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Posted 1 July 2003

Stainless steel combines structural strength with corrosion resistance to form a superior construction material which additionally supports a range of aesthetically pleasing finishes.

The austenitic grades, typically 304 and 316, are most common and comprise 70% to 80% of all stainless steel used. Their popularity is due to their excellent corrosion resistance and mechanical properties combined with their relatively low cost. Nevertheless, the use of stainless steel hollow sections in construction has been restricted in the past by the unavailability of product larger than 150mm x 150mm x 6mm.

Today, however, the stainless steel industry internationally has the capacity to produce hollow sections up to 300mm x 300mm OD (outside dimensions) in thicknesses up to 12.5mm, matching the size range of carbon steel.

Design Codes and Research
The new AS/NZS 4673 gives minimum design requirements for static load bearing stainless members cold formed from annealed or temper rolled materials. Eurocode 3: Design of steel structures, Part 1-4: General rules - supplementary rules for stainless steel is the draft European standard for structural stainless steel design.

According to AS/NZS 4763, pending the release of Eurocode 3 as a European standard, the National Building Code of Finland used in conjunction with the draft Eurocode 3 part 1.2: General rules, structural fire design contains the most specific guidance on fire design for stainless steel members.

Finnish supplier Stalatube Oy has a research program which has concentrated on maximising stainless steel’s advantages as a construction material – corrosion and fire resistance, mechanical strength, easy maintenance and clean aesthetic looks. Good results have been found particularly in relation to work-hardening, which can more than double yield strength, and hold the increased values at temperatures up to 800°C.

Work Hardening
Normal austenitic stainless steel grades cannot be hardened by heat treatment. Hardening is achieved through cold-forming which increases mechanical properties such as the yield and tensile strength. This is particularly desirable in situations where weight is critical, for example in vehicles, or in construction where the design is enhanced by reducing bulk. Enhanced properties result in cost savings as well. The savings potential can be roughly calculated by comparing the enhanced yield strength to the base yield strength.

According to the European standard EC3 part 1.4 the design is based on the strength values shown in the table below.

Grade 0.2% proof stress, MPa min Tensile strength MPa Elongation A80, % min
EN 1.4301 (closest to grade 304) 220 540-750 45
EN 1.4404 (closest to grade 316L) 230 530-680

40

Table 2 below compares the requirements of EC3 part 1.4 (the European standard for design) and ASTM A666 regarding proof stress (yield) and tensile strength values for austenitic stainless steel grades in cold worked state.

Strength class EN 0.2% proof stress, MPa min Tensile strength, MPa min ASTM A666 nearest temper
C700 350 700 1/8 Hard
C850 530 850 1/4 Hard

he Australian Standard AS/NZS 4673:2001
permits the mechanical properties used for designing with austenitic grades to be established by testing of the finished product, ie, instead of testing a sample of the original plate or sheet, a section of the tube can be stretched to failure in a tensile testing machine to find the proof stress and ultimate tensile strengths. This allows the benefits of increased strength due to work hardening to be included when designing structures to the Australian Standard.

 

Over a short period, austenitic stainless steel sustains its mechanical values at higher temperatures than carbon steel. The figure above shows the reduction factors for elastic-modulus for stainless and 0.2% proof stress for an austenitic stainless steel. The sustainability of mechanical values makes it possible to obtain 30 minute fire resistance in stainless steel structures without any additional fire protection. These mechanical values are accepted in Finland as the basis for fire design in structures made of austenitic stainless steel hollow sections. In Australia it is possible to take advantage of the high temperature properties of stainless steels by carrying out fire tests, or by using the results of fire tests in conjunction with appropriate calculations.

The high temperature properties of stainless steel means that in suitable locations the intumescent coatings or other fire protection materials which would need to be applied to carbon steel are not required, allowing the stainless steel framing to be exposed. This is simpler and results in a much improved appearance and could be more economical and environmentally acceptable.

Designing with Stainless Hollow Sections
The qualities of stainless steel favour lightweight, slender structures, with a modern, classy feel and futuristic overtones. The combination of higher mechanical strength at room temperature and fire resistance makes stainless suitable for glass facades and glass roofs, accessways, stairways and balcony structures. A major application area in Australia is air distribution tube in sewage treatment plants.

For those projects where structural loads are being carried and design strength is critical, structural tube with guaranteed mechanical properties can be obtained; this generally implies a minimum 0.2% proof stress of 350MPa.

Designers opting for stainless steel are discovering that there is a wide range of products on the market. For example, Stalatube’s hollow sections begin with 25mm x 25mm tubes used for decorative purposes and go up to 300mm x 300mm (or 400mm x 200mm) for heavy structures with high load-bearing requirements. Profiles above 100mm x 100mm can be manufactured to customers’ own dimensions for maximum cost effectiveness. Australian stock is generally limited to 150mm in square sections although rectangular sections to 200mm x 100mm are available. Smaller sections down to about 12.7mm are also readily available. In addition to the “direct off mill” tube external finish, which is essentially that of the 2B of HRAP strip from which the tube was manufactured, grit polished product is routinely stocked in most common sizes. The polished finish presents an attractive and cost-effective product for visually exposed building components. Grit polished surfaces not only look more attractive in appropriate applications, the finish is also such that welded joints can be blended in, giving a more finished presentation.

Image 1 A 15m high, 230m long copper wall surrounds the Nordic Embassies in Berlin. A load-bearing stainless steel frame inside the enclosure supports the copper panels. The welded frame is made of polished (grit 320) 316 austenitic stainless steel hollow sections measuring 120mm x 120mm x 5mm. Stainless steel was chosen to satisfy low maintenance requirements and to provide a surface which doesn't react with the copper.

Image 2 Nokia House, Helsinki, has a double facade with single glazing 70cm from the front wall. The double facade has many advantages. The air gap between the wall and glazing cover acts as insulation, reducing the need for heating in winter and cooling in summer. It blocks traffic noise when the internal windows are opened and allows ventilation during rainy weather and below zero temperatures.
The load-bearing structures of the double facade are made from 90mm x 45mm x 3mm austenitic hollow sections with the glass fixed on the narrow side. The dimensions were calculated to satisfy the load bearing needs whilst maintaining the deflection needed to avoid the light atmosphere required. The building is located close to both the sea and the main western suburbs of Helsinki where traffic pollution occurs. Grade 316 tubes were chosen for this harsh environment.
Architect Helin & Co Structural Design Matti Ollila & Co

Words by Pekka Yrjola. Pekka Yrjola is a Research & Development Engineer at Stalatube Oy's head office in Lahti, Finland.

This article featured in Australian Stainless magazine - Issue 25, June 2003.


Posted 1 July 2003

Architect Jan Jensen was a consultant to Brisbane City Council on the design of the Brisbane Riverwalk, currently under construction. The walk will take pedestrians from the CBD to the inner suburb of New Farm along the river.

At this proximity to Moreton Bay, the water is brackish and the air salt-laden - it is destructive to most construction materials. Corrosion-resistant stainless steel was chosen for this landmark project to deliver the 100 year service life required by the asset owner.

The structure consists of floating pontoons, reinforced with 316 stainless steel deformed bar. There are stainless steel balustrades and light poles and a suite of stainless street furniture.

Jensen describes the process of specifying the correct finish, including gaining a theoretical understanding and producing prototypes:

The Starting Point
As a key parameter of design responsibility 'value for money' the decision to use stainless steel was an easy one. Our rationale was: "It doesn't corrode and our work is in salt-affected air; it lasts forever; it is low maintenance; it will save us money and keep on looking good."

We needed a specification to let contracts for the manufacture of street and riverscape elements. Writing a specification required describing and reproducing the manufacturing process exactly to get reliable, predictable, consistent and economic results.

Our research took us to ASSDA's timely seminar on the fifty most frequently asked questions about stainless steel, where we were able to ask about tea-staining and how to avoid it.

Then we talked to manufacturers. The answers to our questions about surface roughness and the finishes available made us realise there were variations within the industry and we needed to define our requirements with scientific precision. Specifically, we needed to know the surface roughness (Ra) in microns (µm), as the labels 2B, No. 4 and so on refer to the method used to achieve the finish and comprise an Ra range.

Building Prototypes
We concluded that to write our specification we needed to build the product first to set it within the theory and the 'standard range of common industry manufacturing practice'. We commissioned prototypes of a balustrade and a light pole then the furniture suite for the Riverwalk: seats, bollards, bins, lights, sign posts and drinking fountain.

Forge Brothers Engineering produced the prototypes. It drew on the expertise of ASSDA and its members University of Queensland Materials Performance, 3M Australia, Heat & Control, Condamine Wellscreens, Ronstan International as well as AbrasiveFlex and Dana Ridge.

We soon realised that:

> The common system of finish grades is not a measure of surface roughness, eg the Ra of No. 4 finish products measures anywhere from 0.45 to 0.8µm depending on product form and supplier. Typical Ra for sheet is 0.3 to 0.4µm while it is not unusual for other products such as flat bar to be rougher. Thick plate, thin plate (sheet), tube, flat bar and hollow bar are manufactured by different processes which produce different finishes. The surface finish changes in hot rolled plate and gets smoother as the plate reduces in thickness.

> Ra meters were not commonly used in the industry although their use is growing.

> All abrasives aren't the same. Wear and tear and pressure make a difference. We tested non-woven abrasive belts, Trizact belts, air wheels and silicon carbide.

> The electro-polishing industry uses a variety of chemical baths and voltages.

Towards a Specification
In arriving at our specification we learned:

> Best practice calls for a finish below 0.5µm combined with electro-polishing to eliminate sulphides and increase the chromium content of the exposed surface.

> Wet blasting at low air pressure levels with a water and abrasive bead mix provides a consistent surface finish and economically removes surface variations ready for electro-polishing. This avoids the unexpected rise in roughness which can occur when electro-polishing removes microscopic peaks, previously flattened by mechanical polishing, to uncover underlying pits.

The proof that our specification works can be seen on the Brisbane River. After twelve months in a salt air environment our prototypes are still looking clean and new.

Words by Jan Jensen.

This article featured in Australian Stainless magazine - Issue 25, July 2003.


Posted 1 July 2003

The long-term cost effectiveness of stainless steel makes it a worthwhile proposition even though the initial outlay can be significant. The construction industry is realising that choosing a cheaper, but less durable material can be a false economy.

Eventually repairs need to be made and this can be at considerable expense. Further, there are likely to be logistical problems absent from the initial construction which add to the cost.

For example, when 101 Collins Street – a prestigious Melbourne high-rise office building – was completed twelve years ago, its two 80,000 litre fire water storage tanks were constructed out of bolted steel with a nylon-coated internal surface. Over time the coating had pitted and the steel was corroding, raising concerns about the future reliability of the system.

It was decided that replacement tanks should be fabricated from 4mm thick 316 stainless steel for long-term reliability.

Access was limited because the tanks had been placed in position with the attendant pumps and fire services system plumbing installed beneath them. In fact, a hatch in the floor above the tanks measuring just under a metre square was the only way in and out of the area.

ASSDA member, J Furphy & Sons of Shepparton, Victoria was the successful tenderer for the construction and installation of the new tanks.

The 7.4m long x 2.4m wide x 4.8m deep tanks were fabricated in individual panels, 4.8m x 900mm. With a hoist assembly above, the panels were lowered into position through the hatch and welded in situ. Other challenges to be overcome were creating adequate occupational health and safety conditions and providing welding power and services to the site.

The final step in the project was in situ hydrostatic testing for leaks which proved successful.

The owners of 101 Collins Street can now look forward to many years of worry-free service performance.

This article featured in Australian Stainless magazine - Issue 25, July 2003.

Sculpting Stainless Steel Mesh with Stone

When Canberra-based Artist, Anna Eggert began sculpting with stainless steel wire mesh two years ago she tried every tool to model the material with little success. 

Almost giving up on completing her installation, Eggert reached for a stone and began attacking the 316 mesh in frustration .... with extraordinary results.

The primitive stone became the perfect tool for modelling the wire mesh into soft folds to resemble drapery.

This modelling skill exploits the material to create smooth flowing lines of a garment pressed against a feminine body. It is an effect that effectively breathes life into material to create the illusion of steel 'blowing in the breeze'.

Metal Mesh in Terry Hills, NSW supplied the sculptor with 0.56mm diameter wire mesh with an aperture of 1mm for strength and rigidity. However, various other sizes are often used to create different visual effects.

Two layers of different size mesh can produce a moire effect, with the lines shimmering in and around the material. In the shade, the mesh becomes transparent and in the sun it shines and glitters, it has a life of it's own.

"I was really lucky to stumble upon Wire Mesh Industries in North Ryde (Sydney). They knit stainless steel wire into all kinds of knitted things, car parts, filters and cables, which make beautiful ribbons and belts", says Eggert.

The works are all put together with 3mm stainless steel rivets supplied by Specialty Fasteners in Canberra.

Anna Eggert was recently a finalist in the National Sculpture Prize at the National Gallery of Australia, Canberra. Her latest work "Belinda's Wedding" features a five piece bridal party. The work will be on show until March 2004 as part of a major exhibition of Australian sculpture at the McClelland Gallery in Langwarrin, Victoria.

Photos by David Paterson and Anna Eggert.

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Council Solves Fishy Problem with Stainless

Coastal areas are popular sites for recreational fun and fantastic fishing. However, the City of Albany in Western Australia had one major problem to deal with - fish waste in the nearby waterways 

Local fishermen were cleaning and filleting fish and disposing of the waste overboard. This waste not only stagnated in the water for days, but also attracted seals and stingrays that can become aggressive when feeding.

Faced with a situation of replacing what was a kitchen sink on rusty legs in the water, the Council turned to local ASSDA member, Austenitic Steel Products, to design and fabricate an innovative new stainless steel fish cleaning station for the Emu Point Boat Ramp.

The circular fish cleaning station is believed to be the first and only one of its design currently available in Australia and measures 1400mm in diameter and 1100mm high.

Produced in 316 stainless, the compact design allows six operators at a time and provides a safe environment with no corners or sharp edges.

All plumbing is internal with access only through a hatch on the face of the cone and fitted security locks. Waste water falls to the centre of the table and flows through a circular screen into a collection hopper before entering a two inch waste pipe concealed in the centre.

Initially, the station requires manual removal of offal, but when funding and municipal sewerage is available, the table can be modified to incorporate an automatic processor to pulverise offal into disposable liquid waste.

Albany City's $13,000 station project has generated interest from other Councils and looks set to appear in local boat launching areas, coastal caravan parks and seaside fishing locations throughout Australia.

This article featured in Australian Stainless magazine - Issue 26, November 2003.


Posted 30 November 2003

The humble stainless steel rail is set to become a visual feature with the introduction of an innovative new product that people just can't keep their hands off.

Decorative Tube or Deco Tube has already started making waves on Queensland's Sunshine Coast with a choice between six different patterns suitable for a whole range of applications.

Caboolture Wheelchairs' new Custom Stallion GT design made with stainless Deco Tube.An Expression of Individuality

Caboolture Wheelchairs manufactures a range of customised manual and electric wheelchairs made of stainless steel for disabled people, sporting wheelies, hospitals and nursing homes.

The company sought to transform an ordinary functional wheelchair frame into a stylish feature by using a Deco N8 tube pattern to create a unique, individualised look (pictured below - left).

Unlike most stainless steel applications, wheelchairs are not polished but powdercoated in a range of colours to overcome the stigmatic 'institutional' image.

Caboolture Wheelchairs applies clear blue or red colour powdercoat on the 1.2mm thickness tube supplied by ASSDA member, Tubesales (Qld) to retain the distinct pattern effect.

Ronca Sheetmetal's office foyer display feature fabricated using Rimex sign lettering and stainless Deco Tube.A Distinctive Foyer Display Feature

Caloundra-based ASSDA member, Ronca Sheetmetal wanted to show their interior design clients a myriad of options available to them using stainless steel materials.

Since the office foyer was due for minor refurbishment, the company opted to create a curved display feature wall that doubled as an internal company sign (pictured below - centre).

A Deco N8 tube was used for the feature rail to highlight the new product ... and to impress.

Manufactured in 304 stainless by ASSDA member, National Tube Mills, the feature rail measures 38.1mm in diameter with a thickness of 1.5mm.

This feature rail was complemented with sign lettering using a passivated 6WL stainless supplied by ASSDA member, Rimex Metals.

A feature rail made with stainless Deco Tube in the wine cellar of Sails Restaurant, NoosaA Wine Cellar with Function and Style

Lyndon Simmons, the owner of Sails Restaurant in Noosa loves stainless steel. Simmons has specified so much stainless steel at the popular restaurant location on Hastings Street that staff nickname him the 'Steel Man'.

So it was no surprise that Simmons jumped at the chance to use Deco Tube for a railing in the restaurant's wine cellar when told of the product by Sunrise Hills Welding and Mechanical.

The Noosaville company installed 304 stainless Deco N8 with a 31.8mm diameter and a thickness of 1.2mm.

The contrast of the timber wine racks combined with the stainless steel railings with minimal lighting creates a warm, alluring visual effect that highlights the quality wine collection.

The Deco N8 tube pattern available in six different patterns increasing to nine in the near future.Properties of Deco Tube

Deco Tube is suitable for bending, polishing and powder coating. Ductility does not change and due to the distinctive patern, tensile strength is increased dramatically. In fact, Deco Tube has approximately 70% higher tensile strength than standard tube, due to the cold working, which is required to produce the patterned surface.

Higher strength can result in weight savings by allowing designs in lighter wall thickness, which can be particularly important in the transportation industry.

Deco Tube is also suitable for use as accessories in bathrooms, marine environments or anywhere where safety is an issue.

The product is expected to be popular with Councils, architects, bending companies, boat manufacturers, home decorators and shopfitters.

Marketed by Tubesales (Qld), Deco Tube is designed and manufactured by National Tube Mills, Brisbane with material supplied by ASSDA member, AvestaPolarit (now trading as Outokumpu).

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Chemical Surface Treatments

Successfully using stainless steel depends on environment, grade selected, surface finish, the expectations of the customer and the maintenance specified.

Stainless steels provide robust solutions, but in harsh or borderline environments with high expectations for durability, surface finish will have a substantial impact on performance. Surface finishes can be applied mechanically (usually with abrasives) and chemically.

Understanding how chemical and mechanical treatments will affect the characteristics of the surface and will enable the best possible outcome for the client and the structure. Chemical treatment can be used to improve the corrosion performance of the steel, and hence its appearance in service.

 

Stainless steels resist corrosion best if they are clean and smooth. Clean means being free of contaminants on or in the surface that can either react with the steel (like carbon steel or salt) or that create crevices or other initiation points where corrosion can start.

Smooth means having a low surface area at the 'micro' level. Mechanically abrading the surface can roughen the steel's surface and may also embed unwanted particles.

The common feature of chemical treatments is that they all clean the surface of the steel. They may also smooth or roughen the steel surface, or leave it unaffected depending on which process is chosen. But if carried out properly, they all increase the corrosion resistance.

Corrosion resistance improves as you go to the right of this graph. The graph shows the relative importance of the smoothness of the surface and chemical treatment of the surface. They can be used together to get the best corrosion resistance.

Corrosion resistance improves as you go to the right of this graph. The graph shows the relative importance of the smoothness of the surface and chemical treatment of the surface. They can be used together to get the best corrosion resistance. The study reported by G. Coates (Materials Performance - August 1990) looked at the effect of various methods of treating an artificial welding heat tint on grade 316, 2B surface.

Stainless Steel Products
During steel making, sulphur in the steel is controlled to very low levels. But even at these levels sulphide particles are left in the steel, and can become points of corrosion attack. This 'achilles heel' can be improved greatly by chemical surface treatment.

Most bar products will be slightly higher in sulphur when produced, so chemical treatment to remove inclusions in the surface of these products becomes more important.

Generally mill finishes for flat products (sheet, plate and strip) will be smoother as their thickness decreases.

A No 1 finish on a thick plate may have dimples or other imperfections and a surface roughness of 5 to 6 micrometres Ra.

A typical 2B cold rolled finish on 1.7mm thick sheet might have a surface roughness of 0.2 micrometres Ra or better as shown in Mill Forms.

New surfaces will be created during fabrication processes, (eg cutting, bending, welding and polishing). The corrosion performance of the new surfaces will generally be lower than the mill supplied product because the surface is rougher, or sulphide inclusions sitting just under the surface have been exposed or mild steel tooling contamination may have occurred.

Chemical treatments correctly performed can clean the surface and ensure the best possible corrosion performance.

Chemical surface treatments can be grouped into four categories:

  • Pickling - acids that remove impurities (including high temperature scale from welding or heat treatment) and etch the steel surface. 'Pickling' means some of the stainless steel surface is removed.
  • Passivation - oxidising acids or chemicals which remove impurities and enhance the chromium level on the surface.
  • Chelating agents are chemicals that can remove surface contaminants.
  • Electropolishing - electrochemical treatments that remove impurities and have the added beneficial effect of smoothing and brightening the surfaces.

Pickling
Mixtures of hydrofluoric (HF) and nitric acid are the most common and are generally the most effective. Acids are available as a bath, a gel or a paste.

Commercially available mixtures contain up to about 25% nitric acid and 8% hydrofluoric acid. These chemicals etch the stainless steel which can roughen and dull the surface.

Care is required with all these chemicals because of both occupational health and safety and environmental considerations. HF is a Schedule 7 poison which has implications for sale or use in most states. See ASSDA's Technical Bulletin on this subject.

Passivation
Nitric acid is most commonly used for this purpose. Passivation treatments are available as a bath, a gel or a paste. Available formulations contain up to about 50% nitric acid and may also contain other oxidisers such as sodium dichromate. Used correctly, a nitric acid treatment should not affect the appearance of the steel although mirror polished surfaces should be tested first.

Passivation works by dissolving any carbon steel contamination from the surface of the stainless steel, and by dissolving out sulphide inclusions breaking the surface.

Nitric acid may also enrich the proportion of chromium at the surface - some chelants are also claimed to do this.

Pickling and passivation: before treatment of fuel tanks for storing helicopter fuel on ships. Pickling and passivation (L-R): after treatment of fuel tanks for storing helicopter fuel on ships.
Pickling and passivation (L-R): before and after treatment of fuel tanks for storing helicopter fuel on ships. Photos courtesy of Alloy Engineers and MME Surface Finishing.

Chelants
Chelants have chemical 'claws' designed to selectively clean the surface.

The carboxylic acid group COOH is the basis for many chelants which are used in cleaners, water softening and lubricants. The pH and temperature must be correct for the chelant to do its job. Turbulent rinsing of pipes and vessels afterwards is important.

Cleaning by chelating agents tends to be based on proprietary knowledge and systems, and is less standardised than the other methods described.

The successful use of these systems needs to be established on a case by case basis.

Electropolishing
Most commonly phosphoric and sulphuric acids are used in conjunction with a high current density to clean and smooth (by metal removal) the surface of the steel.

The process preferentially attacks peaks and rounds valleys on the surface and raises the proportion of chromium at the surface.

The technique can have substantial effect on the appearance increasing lustre and brightness while only changing the measured roughness by about 30%.

Precautions
For chemical processes that etch the stainless steel, reaction times will increase with increasing grade.

More care is required with 'free machining' grades and these will usually require substantially less aggressive chemicals. The sulphur addition in these steels makes them readily attacked by chemical treatments. Care is also required when treating martensitic or low chromium ferritic stainless steels.

Detailed recommendations for each grade of stainless steel are given below.

The four categories of treatment are detailed in a number of Standards, but the most commonly used are:

  • ASTM A380 Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems.
  • ASTM A967 Chemical Passivation Treatments for Stainless Steel Parts.
  • ASTM B912 Passivation of Stainless Steels using Electropolishing.

These very useful documents give detailed recommendations on many aspects of selection, application and evaluation of these treatments. Highly recommended reading.

Dirt and grease will mask the surface from treatments outlined above. Therefore, the steel surfaces must be free of these agents before applying chemical treatments.

Many of the chemical treatments described contain strong acids. Before disposal they will require neutralisation. Check with your local authority concerning the requirements for trade waste, neutralisation and disposal.

Many of the chemicals described above will be classified as hazardous substances under State OHS legislation, with implications for purchasing, transport, storage and handling.

Chemical treatments are useful tools in cost effectively achieving peak performance with stainless steels. With appropriate training, hazards associated with their use can be managed.

This technical article featured in Australian Stainless magazine - Issue 26, November 2003.

Specifying Stainless for Suncorp Stadium

PDT Architects, Brisbane in association with HOK Sport, Venue and Event designed and documented the $280m Suncorp Stadium for the Queensland Government.

"It is the top grade material and that's what we wanted for the stadium...

When you take that the client is the people of Queensland, they expect the best to go into the stadium.

If they're paying $280 million for a stadium they want the thing to last and stainless will give you that longevity."

 

Director, John Brown of PDT Architects described the pros and cons of specifying stainless steel for the redevelopment of Lang Park (Suncorp Stadium).

Ticket Counters
When PDT Architects expressed concerns by Ticketek staff that stainless steel ticket counters would be too glary, ASSDA provided the necessary technical assistance required and prevented a switch to timber material.

JB: The client talked about changing from stainless to timber because Ticketek and others had commented that stainless steel would be too glary.

We found that we could use a brushed finish which wouldn’t throw up too much glare and we also did some sun shade diagrams and all sorts of diagrams to make sure the sun wasn’t hitting the ticket counters.

Full Stainless: Commercial Kitchens
JB: It was always going to be stainless steel, mainly because of the health reasons ... but also for cleaniness and ease of cleaning.

All the commercial kitchens at the stadium have them. All the finishing kitchens, all the food outlets, beverage and of course the main kitchen. All the food is prepared in that kitchen and taken up through the service lifts into the finishing kitchens, warming kitchens and then out into the public.

Stainless Wire Rope for Visibility
PDT Architects has recommended replacing the stadium’s flat bar rails with stainless steel wire rope to improve visibility.

JB: We've been able to convince the State Government code people that we can take a lot of the galvanising rails out and put in stainless steel wire rope which would give a better view.

We’ve put in a report to the Government whereby we can cut out a lot of these flat bars and put in stainless steel wire rope through them which will just open the whole place up.

Stadium Stainless Statistics
ASSDA member Fagersta supplied 60 tonnes of stainless steel coil of various widths and thicknesses to ASSDA member Tom Stoddart. A further 10 tonnes of stainless steel was supplied to Eziform for gutters and box gutters.

Tom Stoddart produced works at a cost of $11 million and approximately 50,000 man hours including full kitchen and bar fitouts, refrigeration units, cash register stations balustrading and some food service equipment.

Fagersta was also the main supplier of stainless steel for Colonial Stadium in Melbourne and Telstra Stadium in Sydney.

The Post Game Wrap-Up
JB: Firstly, it satisfied us as far as an architectural feature went, it satisfied us as far as life cycle went and most certainly it then satisfied us as far as safety issues went.

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Savings for Stainless


Posted 30 November 2003

Researchers from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Cooperative Research Centre for Welded Structures (CRC-WS) have developed a welding process for stainless steels and other corrosion-resistant metals that is significantly faster, cheaper and easier than current practices.

The patented process is an elaboration of standard gas-tungsten arc welding (GTAW), and uses a specially designed torch that establishes and maintains a ‘keyhole’ at the joint.

The weld then proceeds, zipper-like, with the melted sides of the keyhole fusing at the back as the torch melts new material in front of it.

Keyhole GTAW is most effective for materials of low thermal conductivity, such as titanium and stainless steel, but does not work with good thermal conductors such as aluminium.

‘In comparison to conventional GTAW, machining of the edges to be joined is greatly reduced, it uses about one-twentieth the filler material, and reduces the welding time by about tenfold’ says Dr Ted Summerville, a commercial manager at CSIRO Manufacturing & Infrastructure Technology in Adelaide.

Applications of the technology include tube making, welding of rotatable products such as pipes and the joining of large sheets. The technology is particularly advantageous for welding thicker materials.

In keyhole welding, the arc melts the metal right through on both sides of the joint. Via surface tension, this establishes a stable structure which joins the front and rear surfaces through the width of the material. The weld pool is thus anchored, preventing the ejection of molten material.

The result is a process which is not only relatively inexpensive to acquire, but is also cheap to operate. The torch melts right through the joint where the two metal pieces to be welded abut, and molten metal extends through the depth of the material – up to 12mm thick for steels and 16mm for titanium alloys.

Very little filler material is needed to make the joint – about 50g/m for welding 12mm thick stainless steel, compared with about 1kg/m using conventional GTAW. And the joint is made in one pass, compared with up to seven for the thickest steels and titanium alloys.

Reduction to a single pass means that the metal at the site of the weld is only at risk of contamination once, whereas if it is welded seven times, there are seven opportunities for contamination.

The lack of multiple passes also vastly increases welding productivity. Typical examples of keyhole performance include single-pass welding of 12mm thick austenitic stainless steel at speeds of 300mm/min, 8mm carbon–manganese steel at 500mm/min, and 3mm ferritic stainless steel at 1000mm/min.

In one comparison, the welding time of 35min/m for 12mm stainless steel plate using conventional GTAW was reduced to <3.5min/m using the keyhole method.

And the quality of the welds is generally excellent. ‘We have qualified the process against a range of American standards’, says Dr Summerville, ‘and it has always passed’.

In addition, it is clean welding process. Fume generation using conventional GTAW is very low, and the same is true for keyhole GTAW.

The drawback to keyhole GTAW is that the torch can only be used in the conventional downhand position – the joint must be made between horizontal sheets with the torch vertical.

Recent work, however, has demonstrated that it is possible to operate the technology ‘out-of-position’, and this could lead to many new applications in the future.

‘If keyhole welding could be done in any position – for instance, if you could rotate the torch around pipe – it would increase the market for the technology by about ten times’, says Dr Summerville.

The technology is currently being licensed by the joint owners of the technology – CSIRO and the CRC-WS – and licencees are already successfully applying the technology in USA and Finland.

A number of licensees in these markets have reported significant productivity improvements.

Licenses for the keyhole welding technology are being offered in Australia, Europe and USA for use in the manufacture of products ranging from spiral-welded pipe to railway rolling stock.

This article featured in Australian Stainless magazine - Issue 26, November 2003.

Stainless Bathing Box of Shattered Dreams

Tamarama Beach or as local Sydneysiders call it 'Glamarama Beach', is well known as the place for beautiful people to be seen and for the rest of us to dream.

 

Artist, Graham Chalcroft set out to distort self-image in the name of fun by capitalising on the beach's former fairground history to design and fabricate a sculpture - 'Bathing Box: the impossible change room of shattered dreams'.

The stainless steel sculpture was a crowd favourite at the 'Sculpture by the Sea' exhibition held in November 2003 from Bondi Beach to Tamarama Beach in Sydney NSW.

The sculpture's design aesthetic was inspired by archival images of traditional late 19th century bathing boxes and how they have evolved.

Each sculpture profile is based on the curves of the human form - one male and one female. On approaching the convex/concave doors, the mirror distorts the body with startling effects.

ASSDA member, Stainless Sections, kindly donated six sheets of 304 with a No. 8 mirror finish for profiles fitted inside the doorframes.

For accuracy and efficiency, Chalcroft use T & M Engineering Group in Smithfield to computer design and laser cut the sheets to be clamped on the structural wood faces and strips.

"The stainless steel performed extremely well. It handled well in fabrication and the thick protective coating saved the steel from potential scratching," said Graham Chalcroft.

"The mirrored steel coped with the heat, wind, salt spray and suffered no scratching from the many thousands of hands touching the artwork," he said.

'Sculpture by the Sea' is in its seventh year and is the largest free outdoors sculpture exhibition in the worlds with over 200,000 visitors.

Photos by Graham Chalcroft.

This article featured in Australian Stainless magazine - Issue 27, February 2004.

Restoring Stainless

Brewed for Efficiency

When Carlton & United Breweries (CUB) announced plans last year to expand production capacity at the Yatala site in Queensland, the company considered both purchase of new stainless tankage as well as transfer of tanks from its Sydney brewery and re-use of second hand tanks in its inventory.

 Six such vessels had been stored by CUB on leased land in the City of Redcliffe, unsealed and exposed to the weather.

Constructed in 321 stainless, the 3 x 12 metre tanks were out of service for the last ten years and placed in the yard for future use.

The six beer storage tanks are part of a series of 16 tanks built in 1966, that have proven the test of time and reinforced the material's durability and returned back to service 'as good as new'.

ASSDA member, D & R Stainless was approached to upgrade the six 1,000 hectalitre (hl) vessels to the new fittings with design verification and tested to meet AS 1220 Standard.

The Brisbane-based fabricator modified, checked and tested the beer storage tanks so as to meet CUB's exacting standards for beer production which would include popular CUB brands such as VB, Fosters Lager, Carlton Midstrength and Crown Lager, allowing them to be used as part of the ongoing expansion.

Work on the six tanks involved cleaning down and refurbishing with new stainless steel tubes and fittings supplied by Matrix Process Solutions.

The six tanks were taken to D & R Stainless and pumped with 4,000 litres of water constantly through the system and back through the CIP spray balls so that all of the tank area was wet to see if there was any carbon steel pick up.

All tanks were checked thoroughly for any rust spots and repolished where required. New nozzles were also installed and internally polished.

D & R Stainless Manager, Ray Powell was initially concerned that the carbon steel supporting rings around the vessel would bleed through onto the stainless as there were no compensating plates.

"We only had one tank [the first tank] that had a problem and that was laminating in the heat effected zones. And that was only on one tank on the bottom of the seams, so we came back in and dye checked, found the problems, ground back and repaired," Mr Powell said.

"The quality of the tank is in good condition. The beauty of stainless is that if it's looked after it will last forever and proof's in the pudding, they're coming up nearly 40 years old - they've certainly proved the test of time," he said.

The expansion of CUB's Yatala facility follows an announcement in April last year of the closure of the Kent Brewery in NSW by February 2005.

This operational review will see the relocation of over 50 beer fermentation and storage tanks from Sydney, a brand new twin stream brewhouse and new filtration equipment to the Queensland facility, which is CUB's most efficient brewery. Total project cost is around $170 million.

As a result of the review, the Yatala facility will double its capacity from 230 million litres of beer a year to over 500 million litres.

Despite being out of service for more than a decade, the excellent condition of the tanks ensures that stainless steel has significantly contributed to product quality and cost efficiency for Carlton & United Breweries long into the future.

This article featured in Australian Stainless magazine - Issue 27, February 2004.

Threaded Fittings to ISO 4144 Standard

For many years there has not been a Standard to cover the low pressure stainless steel cast pipe fittings commonly used in Australia and other countries around the world.

These are commonly termed “150lb” or “BSP” pipe fittings. In most cases the fittings that have been supplied were a mismatch of various Standards.

The fittings were dimensionally in accordance with a number of American Standards, whilst British Standard threads were used. This led to the fittings having threads that in some cases were non-compliant - basically there was insufficient length to accommodate the thread.

ASSDA, through its Technical Committee, identified this problem in the early 90s and through the publication of ASSDA’s Technical Bulletin No 1, highlighted the problems to the Australian market. ASSDA also looked for a mechanism to have these problems rectified.

ISO 4144 "Pipework - Stainless Steel Fittings Threaded in Accordance with ISO 7-1"
After investigating the alternatives it was decided that International Standard ISO 4144 could be the conduit to rectifying the problems. ISO 4144 in its 1979 form covered most of the committee’s concerns, but it did not allow for cast fittings - only wrought stainless steel.

After correspondence with the Australian and International Standard bodies, it was ascertained that ISO 4144 was due for revision, which presented a golden opportunity to have the standard rewritten to cover all of the Technical Committee’s concerns.

ASSDA was invited to represent Australia on the committee established to review the Standard and actively took part in the full process of its revision. Not all of the Committee’s recommendations were accepted. Finally, in early 2003 the new Standard was published.

What has been achieved?
The major improvements that have been adopted in the new Standard are:

a.    The use of castings as well as wrought materials.
b.    All cast fittings are to be properly heat-treated by solution annealing.
c.    The reduction in dimension, a more economical fitting.
d.    The thread standards allowed have been clearly defined.
e.    An introduction of pressure-temperature ratings for application of the fittings.
f.    The inclusion of eight new types of fittings into the Standard.
g.    The inclusion of DN 100 (4”) fittings.

Now that ISO 4144:2003 allows for the use of castings, Australia finally has a Standard that covers the products that have been in common use for many years.

The requirement that all castings are to be fully heat-treated will alleviate some of the corrosion problems that have been encountered in the past.

The dimensions of the fittings have been revised dramatically, thus giving a lighter and more economical fitting.

The wall thickness is the major dimension that has been reduced and it can be reduced by a further 20% if the fitting is made from wrought material.

ISO 7-1 sealing pipe threads are to be used on all fittings. The external and internal threads are to be tapered, but the internal threads may be parallel. The only exception to this is the threads on the Unions and their mating nut, which are allowed to have a variety of parallel threads.

Pressure temperature ratings for application of fittings have been specified (refer to Table 1).

Table 1 - Pressure-Temperature Rating

ome fitting types supplied into Australia were not covered in the old ISO 4144 Standard.

Eight new types have been included in the new Standard: these are 90° Reducing Female Elbows, Reducing Female Tees, 45° Equal Female Elbows, 90° Male x Female Elbows, Crosses, Reducing Nipples, Male x Female Unions and Male x Male Unions.

With the inclusion of the DN 100 (4”) fittings, the Standard now has a comprehensive range of products.

Some Disappointments with the New Standard
In the new Standard, apart from some minor editorial errors, there are two points of concern to the ASSDA Technical Committee.

Firstly, the new wall thicknesses that are stated as minimum could lead to a product being supplied that may not meet the expectations of the customer.

Even though the Standard allows for thin wall product, such thin walled fittings could be subject to distortion during the threading process or during installation. Care must be taken that this does not occur.

The second concern within the Standard is the length of the minimum external thread that has been adopted. The title of ISO 7-1 is “pipe threads where pressure tight joints are made on the threads”.

The minimum length specified can accommodate a thread that seals if it is manufactured to close tolerance. Care is required in manufacture to achieve this outcome.

Although it was recommended to the International Committee that it accept external thread lengths that could accommodate a thread at both ends of the tolerance range, the Committee did not adopt these recommendations.

Table 2 highlights the external thread lengths that were adopted compared to the external thread lengths that were recommended by Australia.

Table 2 - External Thread Length Comparisons

Conclusion
ASSDA believes minimum thread length is a concern to all suppliers and users of these fittings and care should be taken in their selection.

If mating fittings do not seal on the threads and interfere with the washout they may leak.

It is recommended that fittings should only be sourced from reputable and experienced manufacturers and supplied to ISO 4144:2003.

Overall, the Standard is a considerable improvement on what was available, and with care in the selection, the end user will be in a more certain and much safer environment than in the past.

Credits
This article was written by Kim Burton, Group Supply Manager of Prochem Pipeline Products Pty Ltd and an ASSDA Technical Committee member. ASSDA also acknowledges the contribution of Technical Committee member Peter Moore, Technical Services Manager of Atlas Specialty Metals, in the development of this article.

Download Technical Bulletin (April 1997 - pdf 920k)

This technical article featured in Australian Stainless magazine - Issue 27, February 2004.

Cleaning and Protecting Stainless Sculptures

"Windhover" is a dramatic stainless steel sculpture created by the late Lenton Parr, located on the eastern foreshore of Port Phillip Bay in Sandringham, Melbourne.

Unveiled in December 2001, the sculpture's vertical lines and arcs are evocative of the yachts often seen sailing out on the Bay.

However, two and a half years of zero maintenance and exposure to salt spray from the bay have taken their toll, turning the surface of the stainless steel a blotchy brown.

Called tea staining, it's caused by deposition of salt on the surface which is then trapped in the crevices of the brushed finish.

Regular reactivation by rain has perpetuated a corrosion cycle leading to quite rapid and severe surface staining.

The problem was how to clean the sculpture and then to ensure that it would remain protected from tea staining in the future.

Conventional weld pickling products containing hydrofluoric acid are very aggressive and risk damage to or discolouration of the surface.

Strong acids may also create an environmental and safety hazard when used in such a public place.

Many cleaning formulations are available based on phosphoric, sulphamic, oxalic or nitric acids. They have various degrees of handling and disposal restrictions.

The formulations may also contain mid abrasives and wetting agents/detergents to aid the cleaning process.

In July 2004, ASSDA Member, Revolution Advanced Metals and Materials, used a cleaning paste based on a moderate concentration of phosphoric acid which is relatively safe to handle.

Inadvertent skin contact by this product does not cause the burning and possible ulceration associated with strong concentrations of nitric and hydrofluoric acid preparations.

The cleaning product was brushed on and left to react for 3-4 hours. The brown tea staining gradually disappeared.

In some particularly bad sections a second application was necessary to completely remove all traces of the staining, but it left a completely blemish-free surface.

In this case, residue from the cleaning product was simply washed away with water. In other cases, however, check with local authorities for correct disposal procedures.

One of the problems when washing stainless steel with water is the streaking caused by uneven drying.

This was very noticeable on the sculpture.

Also, because it is unlikely that ongoing regular cleaning will occur, it is also important to limit the access of chlorides to the surface. Otherwise the staining problem will recur.

To overcome both these problems, a water-based protective product with oils and non-ionic surfactants but no phosphates was sprayed on and wiped over.

After polishing with a dry cloth all streaking vanished. It left an invisible film that stopped further streaking and fingermarks.

Best of all, it brought up the lustre of the brushed finish, and left Windhover looking as good as the day it was made.

Regular re-application should maintain the finish and help prevent tea staining in future.

Correct design, fabrication and on-going maintenance will all assist in keeping stainless steel sculptures and other structures erected adjacent to the coast in good condition.

Words and images courtesy of Jim Picot, Revolution Advanced Metals & Materials.

This article featured in Australian Stainless magazine - Issue 29, September 2004.

Crevices and Corrosion

A crevice is a narrow gap between a piece of metal and another piece of metal or tightly adhering material like plastic or a film of bacterial growth.

Many metals and alloys are susceptible to crevice corrosion, but in stainless steel, crevices are the first and most common place for corrosive attack to begin. With a little understanding, crevice corrosion can either be avoided or minimised.

Crevices can be:
• The space under a washer or bolt head.
• The gap between plates bolted together.
• The gap between components intermittently welded.
• The space under a sticky label.
• The space between a gasket and the metal in a flange (especially if the gasket is absorbent).
• Any other tight gap.

Crevices can be designed into the structure, they can be created during fabrication or can occur during service.

Prevention measures should therefore also aim at design, fabrication and service.

Why crevices can corrode
To work at its best, stainless needs free access to oxygen. Crevices are wide enough to permit entry of moisture, but narrow enough to prevent free circulation.

The result is that the oxygen in the moisture is used up. In addition, if chlorides are present they will concentrate in the stagnant conditions and, by a combination of reactions, the moisture can become acidic.

These are all conditions that can lead to the breakdown of the passive film on the stainless. Attack can then progress rapidly.

Crevices can create conditions much more aggressive than on adjacent surfaces. Having crevices builds in weak spots where attack can begin and begin in much less severe conditions than anticipated for the remainder of the structure.

Table one shows laboratory measurements of critical temperatures needed to cause pitting on an open surface (CPT) and crevice (CCT) attack of a metal plate beneath a PTFE washer in a 10% ferric chloride solution.

The CCT is at least 20˚C lower than the temperature to cause pitting corrosion in this aggressive liquid. (Ferric chloride solution is an aggressive corrodent and is used because it is similar to the liquid in a pit when it is actively corroding.)

Factors influencing crevices:

Crevice Shape
The geometry of the crevice will influence its susceptibility to attack and the speed of progress. The narrower and deeper (relative to its width) a crevice is the worse attack will be.

Metal to flexible plastic crevices tend to be narrower than rigid metal to metal gaps so metal to plastic joints provide more aggressive crevices.

Environment
The more aggressive the liquid outside the crevice, the more likely it is that the crevice will be attacked.

This is why crevice attack can be a problem in a salty swimming pool but not in a fresh water tank.

In the atmosphere, crevices beside the sea give more problems than in rural environments. If the liquid outside the crevice is very oxidising, eg with bleach, hydrogen peroxide or ozone, then crevice attack will tend to be more severe.

Temperature
Once the CCT is exceeded, then as with pitting corrosion, higher temperatures mean corrosion is more rapid. The rule of thumb is that a 10˚C rise in temperature will double the corrosion rate.

This means that when comparing Far North Queensland to Tasmania, not only are crevices more likely to start corroding but also that once they do, they will corrode faster because the temperature is consistently higher.

Alloy resistance
Using a more corrosion resistant alloy gives less crevice attack. For example, in seawater at ambient temperature, crevices will form on 304 if there is a 0.9mm gap, on 316 if there is a 0.4mm gap and on 904L (similar corrosion resistance to 2205) if there is a 0.15mm gap.

Minimising the risk of crevice corrosion

Good design, fabrication and operating practices will anticipate and hence minimise crevice corrosion.

Design
Design to minimise the occurrence of crevices.  If a crevice is a necessary part of a component’s design – can it be made wider?

Full penetration butt welds are best for joints.  Seal lap joints and avoid gaps between pipes and fittings.

Minimise use of bolted connections and other fasteners. Where crevices can’t be avoided use a steel grade resistant to crevice corrosion in the operating environment. It is also possible to seal the crevices to keep out corrosive liquids, but care must be taken that the seal is permanent.

Be careful that the sealant “wets” the surface. If it doesn’t it may form its own crevice. Sealants that dry and shrink can form their own crevices.

Gaskets between flanges will probably form a slight crevice, but if the gasket does not absorb the liquid and is compressed between the surfaces (and not bulging around the flange), then the crevice is usually shallow enough so that crevice corrosion is not a problem.

Fabrication
Ensure full root penetration of welded joints with smooth weld bead. Avoid under cut and cracks in welding. Use of sticky labels or markers of various kinds (such as crayons) should be avoided, as should smears of grease or oil.

“Smooth and clean” at all times. ASSDA Accredited Fabricators are assessed on their knowledge of crevice corrosion.

Operation
Sediment and scale can both result in crevices.

If the problem can’t be designed out, routine maintenance will minimise risk. Crevice corrosion under bacteria film can occur. Maintaining circulation reduces the risk that debris will collect and form crevices in dead legs or low flow areas.

Further Reading
The Nickel Institute’s free publication #11021 “High Performance Stainless Steels” contains much of the information used in this article.

This publication and a mathematical model useful for assessing crevice corrosion risk can be downloaded from the Nickel Institute website - www.nickelinstitute.org

If more detailed corrosion mechanism information is required, then “Corrosion of Stainless Steels” by A. John Sedriks is a good intermediate point.


Reinforcing pad, staggered welds - adequate strength.


Reinforced pad, seal weld - best corrosion resistance.


Staggered fillets - severe crevice


Continuous fillets both sides - crevice sealed


Figure 1: Typical crack defects around a weld (WTIA)

Credits
The Australian Stainless Steel Development Association (ASSDA) would like to acknowledge the contribution of the following Technical Committee members for their contribution to the production of this article.
•  Richard Matheson - Executive Director, ASSDA
•  Graham Sussex - Technical Specialist, ASSDA
•  Peter Moore - Technical Services Manager, Atlas Specialty Metals

This article featured in Australian Stainless magazine - Issue 29, January 2004.

Versatile Style with Stainless Decorative Tiles

A revolution is about to take place in the tiling industry with the introduction of stainless steel decorative tiles with a versatile design that will add style to any kitchen, bathroom, restaurant, bar and even as a feature wall.

There are many benefits to using stainless steel tiles. The tiles cannot burn or crack, graffiti can be easily removed, will not rust and is a stylish upgrade to the standard one piece splashbacks.

Available from Futura Tiles (Border Sheetmetal), the tiles are available in a wide variety of sizes, patterns, finishes and grades. Size ranges include: 65 x 290mm freeze, 290 x 290mm tile, 390 x 390mm tile.

Runaway Bay Designer Builder, Kerri Phillips, was so happy with the product that he installed the stainless tiles in his own kitchen and found cutting the tiles no problem at all.

"They provide you with special blades. It's a delicate operation, as long as you're careful it's fine," says Phillips.

ASSDA major sponsor, Fagersta Steels, supplies grade 304 stainless and patterned sheet from ASSDA member, Rimex Metals to Futura Tiles (Border Sheetmetal) to produce the tiles.

The tiles are also available in various Rimex patterns and finishes including the standard brush finish, 5WL and 6WL surface finishes.

Manufactured from grade 304 stainless as standard, the tiles are also available in grade 316 stainless for applications with a close proximity to marine environments.

Installing stainless steel tiles
Stainless steel tiles are basically the same as laying most floor and wall tiles. Cut tiles using similar ceramic grinding methods by using blades with 1mm steel cutting wheels.

Grouting
When grouting, apply grout to tiles leaving the protective film covering on the face of the tile. Use only fine, sanitised water resistant grouts and do not apply sanded or abrasive grouts. Remove excess grout with a clean sponge leaving a smooth grout line.

Removing film covering
Peel the protective film covering from the tiles, then with a clean sponge, remove any grout left behind from the edges of the covering. Leave approximately 30 minutes and dust off with a clean lint free cloth.

Protecting
After all dust film from the grouting has been removed apply a small amount of polishing oil to a clean rag and wipe with the grain of the tile to remove any excess oil. This will resist finger printing and water spotting and will enhance and protect the stainless steel surface.

Images courtesy of Karl Johnson, Futura Tiles (Border Sheetmetal).

This article featured in Australian Stainless magazine - Issue 29, September 2004.

Stainless Steel Enhances Hayman Island Views

North Queensland's Hayman Island Resort welcomes thousands of guests every year to the Great Barrier Reef island destination. Also attracted by the beauty of the resort, cockatoos have eaten away at the timber balcony railings and balustrades

 

To combat the work of the troublesome cockatoos, the resort management called for stainless steel to replace the timber railings and balustrades on the fifteen year old building.

ASSDA major sponsor, Atlas Specialty Metals, supplied approximately 1,000 linear metres of grade 316 stainless steel including 76 x 42mm oval tube and 38mm diameter round tube in high polish to Mackay-based fabricator, Jeff Eales Sheetmetal for the project.

Stainless steel was used extensively for the balcony top rail and posts on all three levels of the pool wing accommodation block. Because many of the balconies are at the edge of the pool, oval profile tube was specified to prevent glasses or bottles being placed on the rail and then being bumped into the pool.

Also, to ensure guests receive uninterrupted ocean views, stainless steel wire rope was installed on each of the balustrades. This helped to eliminate the restricted views given by the previous timber material.

ASSDA member, Arcus Australia Pty Ltd supplied stainless steel wire for the balcony balustrades and ASSDA member Bridco supplied the wire fittings, turnbuckles and swages for the resort balustrading redevelopment.

Guests have commented on how the use of stainless steel complements the surroundings, improves the views and suits the building style.

Hayman Island Resort management are also impressed with the new stainless steel railing as it stops the bird problem, requires low maintenance and is easy to clean. All these qualities make the tropical ocean views much better.

This article featured in Australian Stainless magazine - Issue 30, January 2005.


Posted 31 January 2005

Sydney's New Year's Eve has always been celebrated in spectacular style and this year's event shined with the inclusion of a giant glitter ball featuring stainless steel.

Hanging from the Sydney Harbour Bridge was 'Fanfare', a five storey-high spherical structure covered in 354 stainless steel pinwheels that spin as the ball rotates.

The sculpture, designed by New Zealand artist Neil Dawson, is Sydney's first three-dimensional bridge effect in the event's history.

ASSDA major sponsor, Sandvik Australia Pty Ltd and ASSDA member, Stainless Sections supplied 90 sheets of 10' x 4' x 1mm or approximately 2.7 tonnes of stainless steel in number 8 finish to ASSDA member, DME Engineering Services for the fabrication of the pinwheels surrounding the structure.

During the day the pinwheels of  'Fanfare' spin in the winds of Sydney Harbour reflecting the many colours of the sky. At night the sculpture becomes a part of the light show, acting as a canvas for projections and reflections.

This article featured in Australian Stainless magazine - Issue 30, January 2005.

Solving the puzzle with stainless mainline fittings

Choosing mainline fittings for irrigation applications can often seem like building a giant puzzle with elbows, tees, crosses and coupler sets - various fittings required to connect irrigation pipework together.

Pierce AustraliaHowever, Geoff Mellows from Yarrawonga Irrigation in Victoria may have solved the puzzle by using stainless steel mainline fittings - something that plastic fittings cannot yet match.

Poly, pvc and avs fittings are common materials in irrigation applications but because they are produced out of a mould, the combinations of size and outlet configuration are restricted.

Mellows said that by using stainless mainline fittings by ASSDA member, Pierce Australia, he can now “manipulate the angle, the shape, the variation and combination of outlets.“

The difference is simple. PVC and poly are bolted on, or welded and glued - making it difficult to change fittings”.

Stainless steel mainline fittings are the only rubber-ring jointed fittings available on the marketplace manufactured to the customers specific needs and can be fitted on any other combination because they are fabricated.

Stainless steel mainline fittings also provide flexibility of design in the angle of the fittings.

This also applies to the combination of outlets on those fittings and any other additional connections to that fitting.

With versatile stainless steel fittings, Mellows advice to customers is simple - “lay the pipe first and worry about the fittings later!”

This article featured in Australia Stainless Issue 28, May 2004.

Photos courtesy of Pierce Australia.

Stainless technology to remember war heroes

The Australian War Memorial in Hyde Park Corner, London stands as a symbol of freedom and an enduring spirit of strength.

To commemorate the men and women who fought and died for Australia alongside Britons in the two World Wars, Australian architectural firm Tonkin Zulaikha Greer and artist Janet Laurence designed the Memorial to reflect the sweep of the Australian landscape.

The result was a highly durable structure featuring a long, curved wave wall constructed out of West Australian green granite and supported by grade 316L stainless steel.

ASSDA Major Sponsor, Atlas Specialty Metals, and ASSDA members, M & S Stainless Supplies and Dalsteel Stainless supplied approximately 9000 kilos of stainless steel for the structure including 8mm plate, pipe, angles and 3mm sheet.

Grade 316L was specified for its corrosion resistance, particularly as the Memorial comprises a water feature that periodically cascades water across the wall to highlight the names of the hometowns of our soldiers.

Stainless steel was used primarily in the construction of stainless steel cradles which were fabricated in Australia, shipped, positioned and lifted into place to support the granite.

All welds were pickled and passivated to provide protection from the bromine and chlorine’s likely to be deposited on the frames from the water forms built into the Memorial.

Australian-based firm Design and Survey Neon (DSN) played a leading role in the design and manufacture of the supporting structure by using 3D modelling techniques.

The 3D modelling allowed the manufacture of components and assembly of the job to become a seamless process.

DSN modelled the granite wave wall and supporting cradles. The templates for the granite blocks and their fixings were then lifted from the model to enable the fixings to be pre-drilled prior to assembly.

The use of laser cutting and CNC technologies allowed DSN to fabricate to near machining tolerances. Laser etching of assembly notches were added for simple fabrication and installation.

Coordinates for supporting cradles from the model were used to determine correct on-site positioning via electronic theodolites.

The granite blocks were positioned with a 6mm gap vertically and horizontally to a tolerance of plus or minus 1mm. Precise accuracy was required to avoid accumulation of errors because of its wave like design.

Most of the components for the Memorial were imported from Australia. Water features and water effects were created by Waterforms International and all the stone work was assembled by Australians.

This article was featured in Australian Stainless Issue 28, May 2004.

Photos courtesy of Department of Veteran Affairs & Design and Survey Neon (DSN).

Main image: The Australian War Memorial 'Dedication Day Wreaths' placed in front of the curved granite wave wall. Photo courtesy of the Department of Veterans Affairs, copyright Commonwealth of Australia. Reproduced by permission.

Other images: 316 stainless steel cradles were lifted into place to support the granite blocks that form the wave wall.

Cleaning of exterior stainless steel

The visual performance of outdoor stainless steel depends on five interrelated factors:

• Surface finish - smooth and clean and free of crevices.
• Grade selection - appropriate for environment.
• Good design - rain washing and uniform draining.
• Maintenance program - regular cleaning.
• End user expectations.

This technical article provides suggestions on a maintenance program for cleaning of exterior stainless steel, together with some recommendations for remedial action if stains occur beyond regular maintenance or where such maintenance has not been performed.

Maintenance: routine removal of grime

Stainless steel holds its appearance best if it is washed regularly. When washing use soap or detergent or 1% ammonia solution in warm, low chloride water with cloths or soft brushes to avoid scratching the surface.

Smears will be reduced if the surface is dried afterwards. This treatment applies to bare stainless steel but care should be taken with coloured surfaces.

Coloured and very smooth finished (eg BA or No. 8) surfaces subjected to excessive brushing or rubbing may lose gloss or even become scratched. Bleaches are not recommended.

Simply wiping with a damp cloth is not adequate as it smears corrosive deposits without removing them.

Table 1 from the ASSDA ‘Tea Staining’ Technical Bulletin provides a guide to the recommended frequency for cleaning exterior stainless steel. This Bulletin is available for viewing or download from ASSDA’s website.

Grease, oily films and other organic contamination

Oils and grease may be removed by alkaline formulations or hot water and detergents or, if necessary, by hydrocarbon solvents such as alcohol, acetone or thinners or eucalyptus oil. In all cases the surface should be rinsed with clean water and preferably dried.

For directionally grit polished finishes, wiping along the polish direction with very hot clean water and a soft, absorbent cloth is a good final step to reduce smears.

Heat from a hair dryer or glue gun may soften adhesive remnants from labels or protective films for removal.

After exposure to UV degradation from sunlight, adhesives may require similar treatment to grease stains or even abrasion, with the probability of a bright or scratched spot.

Adherent Scales and Mortar

Adherent scales and mortar may be removed chemically but NOT using chemicals containing chlorides.

NEVER use brick cleaning liquids that contain hydrochloric acid. Hot 25% acetic acid (vinegar) or warm 10% phosphoric acid are effective in removing hard water scales and dried mortar splashes.

Following the acid wash, the surface should be neutralised with dilute ammonia or sodium bicarbonate solution, rinsed and dried.

Remedial Work

The brown surface stains that can occur on stainless steel during atmospheric exposure are simply cosmetic rust stains.

This brown ‘tea staining’ on stainless steels will not progress to potential structural damage as could occur with a carbon steel structure.

The procedures outlined below may enable you to remove the tea staining. However, if the progression of damage is beyond these recommendations it is advisable to employ an experienced contractor.

Cleaning Rust Stained Flat Surfaces

Early action after the onset of tea staining is desirable, before the appearance of the underlying surface is changed.

If the surface is pitted, then it is probable that it will require mechanical repolishing. After mechanically cleaning off tea staining, it is preferable to passivate the surface by using a nitric acid gel or, if the item is portable, by immersion in a nitric acid bath. For marine exposures, passivation is very strongly recommended.

In contrast to other acids, nitric acid is a strong, oxidising acid cleaner and has the added advantage that it is a passivating agent.

The Nickel Institute has suggested that rust may be removed by the use of a 10% phosphoric or oxalic acid followed by a 1% ammonia solution neutralisation and then a water rinse.

Alternatively a mild acid based cleaner such as sulphamic acid (used in some saucepan cleaners) can be used with some care to avoid local changes in appearance. NEVER EVER use hydrochloric or sulphuric acids.

There are also proprietary chemical cleaning treatments often based on citric acid or other chelating compounds. Although these agents passivate in the sense of removing free iron and other foreign matter, they do not augment the surface oxide film.

Use of liquid acids on site is generally unsatisfactory as contact time is short and the acid may run off and damage adjacent components.

Unlike the hydrofluoric acid pickling process used after welding, a nitric acid passivation process does not normally change the surface appearance of stainless steel, although it may cloud a mirror polished surface. Careful trials on inconspicuous areas are recommended prior to full scale cleaning.

Electropolishing is also used by some contractors to smooth rough edges and both clean and passivate the surface. It can be carried out on site or, more usually, in purpose-built tanks.
Afterwards – prevention of recurrence

If tea staining has occurred, one or more of the five factors outlined in the introduction have not been considered carefully enough when the structure was designed and/or built.
To improve the structure, the following steps may be taken to prevent recurrence:
• Increase the frequency of maintenance.
• Improve the surface finish - mechanical polishing and chemical treatment on-site.
• Alter the design of the structure - redesign and replace the affected part of the structure.
• Improve grade selection - replace the structure with a more suitable grade of stainless steel.


ABOVE: A successful stainless steel installation in an outdoor application.

If consideration of the aforementioned steps indicates an uneconomic result, the stainless steel can be painted.

Paint systems using lacquers and polyurethane top coats are available and have been used successfully, but care and understanding is required.

Painting the stainless steel is a step that should only be used as a last option as it is irreversible.

This technical article was published in Australian Stainless Issue 28, May 2004. It is an extract of a Technical FAQ on ‘Exterior Cleaning of Stainless Steel’.

For technical support and advice contact ASSDA on 07 3220 0722 or email This email address is being protected from spambots. You need JavaScript enabled to view it.