3 Corrosion Risks in Food-Grade Stainless Steel
Great attention needs to be directed towards preventing corrosion in stainless steel which is used in the food processing industry. In some facilities, the conditions favour certain forms of corrosion. This article discusses risk factors you should address when you are selecting stainless steel products.
Crevice and Pitting Corrosion
Pitting corrosion occurs when deep pits form on small areas of plain surfaces. Crevice corrosion takes place when fluids stagnate in narrow crevices or sharp corners in stainless steel objects.
These two forms of corrosion are likely to occur if the stainless steel surfaces come in contact with acidic fluids. Aqueous solutions with chlorides in them can also accelerate the rate at which crevice and pitting corrosion may occur. The chance of this type of corrosion also increases when the mentioned fluids are present at an elevated temperature.
Crevice and pitting corrosion can be prevented by selecting cleaning products which don't contain the substances mentioned above. Product design can also reduce the risk by eliminating the sharp corners or edges which can trap fluid molecules and trigger corrosion.
Intergranular Corrosion
Stainless steel is also susceptible to intergranular corrosion. This type of corrosion is typically seen in areas around a weld seam. 'Weld decay' is another name for this form of corrosion. The weld seam decays due to the depletion of the chromium in that area as a result of reactions with air during the welding process. Carbon is therefore left exposed to agents of corrosion.
Intergranular corrosion can be prevented by selecting stainless steel which has a low level of carbon in it. Shielding the steel from ordinary air and moisture during the welding process can also avert chromium depletion.
Stress Corrosion Cracks
Stress corrosion cracking happens when high temperatures combine with corrosive fluids to undermine the corrosive resistance of stainless steel. Chlorides are particularly notorious for triggering this type of corrosion. The use of chlorides during cleaning or other processes should therefore be avoided when the stainless steel products, such as process pipes, are still hot.
No amount of corrosion is tolerable in the food and pharmaceutical industries. Extreme care should therefore be taken when selecting stainless steel and the fabrication techniques which will be used to make equipment. Rigorous inspections should also be done on a regular basis in order to identify signs of corrosion so that immediate action can be taken. Failure to do so could compromise the products being manufactured.
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