Removing Iron and Stainless Steel Contamination
Any cleaning process that can remove embedded iron can be used. It is important to ensure that all the contamination is removed or not spread to other areas of the stainless steel product surface, otherwise rust staining can recur. In this respect, chemical, rather than abrasive cleaning may be advisable.
Cleaning and iron recontamination is well documented in stainless steel cleaning product suppliers literature and literature published by the Nickel Development Institute.
As with cleaning, a stepwise approach, depending on the severity of the staining should be considered. Nitric acid or nitric / hydrofluoric acid preparations are the most effective but may cause surface etching, which may be unacceptable on the restored item.
Methods for removing 'iron' contamination
Mild staining or surface 'bloom'. Mild-non scratching domestic cleaning creams or polishes can be used. These usually contain calcium carbonate, with surfactant additions. 'Jif' kitchen cream cleaner (Lever Brothers Ltd) is an example of such a product. Domestic stainless steel cleaners, which may contain citric acid can also be used. Shiny Sinks -(Home Products Ltd) is an example of such a product.
Fresh iron / steel grinding grit or dust
A saturated solution of oxalic acid, applied with a soft cloth or cotton wool and allowed to stand for a few minutes, without rubbing or abrading. This should etch out the iron particles, without leaving scratches or significantly altering the surface texture of the stainless steel.
Moderate rust staining
Phosphoric acid cleaners can be effective if sufficient time and care is taken, with minimal risk of etching the surface. Alternatively, dilute nitric acid should remove small amounts of embedded iron and will help repassivate the cleaned surface.
More severe rust staining
Nitric acid / hydrofluoric acid pickling preparations should remove more embedded iron than nitric acid alone. Surface etching is likely and so complete restoration to the original finish and surface texture may not be possible. If these preparations are left on stainless steel surface too long, pitting can be caused.
There is a limit to what can be achieved. Although contamination may be removed, these treatments will not remove any pitting associated with severe staining. In such cases mechanical grinding may have to be considered to 'bottom-out' the pits which means that a complete restoration of the surface will then be needed.
Iron Contamination and Rust Staining on Stainless Stee
Avoiding Iron and Stainless Steel Contamination
Testing for Iron and Stainless Steel Contamination
Removing Iron and Stainless Steel Contamination
Cleaning methods for Stainless Steel
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