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How To Avoid Stainless Steel Contamination
11 May 2016
Stainless steel contamination occurs when the thin passive film on the surface of the metal is permanently damaged, resulting in corrosion. This surface contamination not only negatively impacts the aesthetics of the steel but can also affect its performance, so avoidance should always be a primary objective.
There are many possible sources of stainless steel contamination including fabrication methods, chemical environment, temperature, product design, carbon steel particles, paint, grease, oil, dust, grime, salt and free metals such as copper, zinc, lead, brass and aluminium. Errors can be costly and difficult to fix so prevention is always a far better course of action.
In the steel fabrication industry, fabricators need to follow very careful storage and handling practices in order to prevent stainless steel contamination and it goes without saying that there’s a correlation between the possibility of contamination and the quality, expertise and experience of the steel fabricator.
Here are some key ways that fabricators can avoid stainless steel contamination:
‘Mixed’ fabrication shops carry a high risk of contamination. Fabricators should have designated areas for both their stainless steel and carbon steel inventory and their fabrication processes. These areas should be kept separate – preferably by physical means such as a wall.
The stainless steel should be protected by plastic or other wrapping to prevent iron filings and other contaminants from settling on the surface and causing damage.
Eliminate possibility of iron or steel dust particles
Loose and embedded iron particles are one of the most common sources of contamination. Many workshop activities such as grinding, blasting, welding and machining produce spatter, filings or dust and this debris can land on the stainless steel and contaminate it. It’s therefore imperative that carbon steel is always handled well away from stainless steel.
Keep tools separate
Fabricators should ensure there’s no contamination from shared tools, equipment and storage fixtures.
Dedicated tools for processing and handling stainless steel are imperative and fabricators should only use tools that are fit for purpose when handling stainless, e.g. carbon-free cutting discs and hammers manufactured from hardened chrome plate.
Sound handling practices
When handling stainless steel, plastic or plastic covered wraps or ropes are preferable. If carbon steel bands are used (which they often are), then cardboard padding or other suitable packaging material (e.g. wood) should be placed on top of the stainless steel to prevent contact with the carbon steel.
Stainless steel sheets should be stored horizontally in a wooden box and covered to prevent contamination from airborne debris, whilst plate should be stored vertically in a dry, covered area. This will also avoid the possibility of impregnating or damaging the surface of the material with corrosive particles (such as iron filings) by walking on it.
Keep it clean
A high standard of cleanliness in the working environment is essential. Fingerprints, chalk marks, paint, oil, grease can also initiate damage, and the stainless steel should kept as clean as possible. It’s best to use a cleaning agent or acid that has a pickling or passivating effect (i.e. which will help the surface layer to replenish itself) but due care and caution must be taken with these as they can be aggressive.
A professional steel fabricator like WA Steel knows how important it is to avoid contamination throughout all stages of the lifetime of the stainless steel item from storage and handling through to fabrication and service life. They have a proud 30-year history as a leading specialist steel fabricator in Perth and if you’d like to see their workmanship, their facilities or their expertise in action, contact them on 08 9377 3778 or or visit their website, www.wasteel.com.au.