The contamination of stainless steel occurs when the stainless comes into contact with an iron object, for example a tool, and as a result the iron particles are ‘smeared’ onto the stainless. When put in a corrosive environment (think most cities on the coast) these iron particles rust, leaving a very unsightly brown rust. The contamination often isn’t apparent until after the installers have left the site but sooner or later, the invisible iron particles will probably rust. This doesn’t look good, and can not only harm the reputation of the installer, but require them to return to the site to remedy the problem.  To help you avoid this headache, we would like to share some tips gleamed from our 20 years of experience:

Avoid Contamination from Tools

• Drive/Screw Tips should be chrome vanadium steel. Chrome vanadium protects the iron in the tool from coming into contact with the fastener;
• Allen keys and security screw tools should be hardened chrome plated.
• Cuttings discs should be made from aluminium oxide, be ‘iron’ or ‘carbon – steel’ free, or be labelled ‘for stainless steel’.
• Hammers should be good quality hardened-chrome plated steel or stainless steel.
• All tools for stainless steel should be kept separate from others and be used exclusively for stainless steel.

Consider Iron Particles in the Environment

• Keep stainless steel products protected from iron in the environment. A classic example is iron filings from grinding and cutting carbon steel on site flying around and ending up all over the stainless. Sooner or later they will be leaving rust marks. So cover the stainless in plastic sheet/wrap until the job is completed.
• This applies to the workshop too – physically separate (preferably with a wall) ‘carbon-steel’ fabrication from stainless steel fabrication.
• Maintain a clean working environment where possible ensuring that immediate working areas are free of any metals filings or particles of aggregate.
• Protect stainless steel from general workshop grime, weld spatter and grinding sparks.
• Avoid walking on stainless steel products with footwear that can damage or impregnate the surface of the material with corrosive particles.

Handle Stainless Correctly

• Don’t use steel straps for packaging. Instead use plastic or plastic covered straps and/or ropes for retaining or lifting stainless steel. It is important to ensure that ropes or straps are themselves free from iron contamination, for example they may have been used to tie steel. Ideally have straps just for use on stainless.
• Don’t use solvents containing chlorine.
• Use marking inks with low chloride content.

 Next month we will be discussing how to clean surface contamination.

For more information on how best to avoid contamination of stainless. Visit the following links:

• Dos and Donts of using Stainless Steel
• British Stainless Steel Association Article - Iron Contamination and Rust Staining on Stainless Steel

NB: This information is provided as a guide only and Anzor does not accept liability for the application of this information. For advice about stainless steel contact the NZ Nickel Institute