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Stainless doesn't mean rust-proof - Soundings Online

Stainless doesn't mean rust-proof

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As far back as 1821, French metallurgist Pierre Berthier recognized the advantages of iron-chromium alloys — essentially a mix of the two elements through melting.

As far back as 1821, French metallurgist Pierre Berthier recognized the advantages of iron-chromium alloys — essentially a mix of the two elements through melting. Objects made from the alloy didn’t rust as quickly and weren’t as prone to staining, and Berthier thought it would be great for use in making cutlery.

Read the other stories in this package: Waxing tips from the pros   Don’t ignore your stainless steel

Advances in metallurgy eventually led to the development of more than 150 grades of stainless steel. Most are susceptible to corrosion and are unfit for use on boats. Marine grade stainless steel (SS316) is the most corrosion-resistant because it’s alloyed with higher percentages of chromium and nickel, and because it contains molybdenum, an element added to SS316 to enhance its corrosion-resistant properties. But all grades of stainless steel, including SS316, also have iron in them, and when iron is exposed to air it rusts.

The chromium in stainless steel forms a very thin, invisible layer of chromium oxide on the surface when oxygen is present and the surface is clean. The layer acts as a buffer, keeping water and air away from the metal and making the iron in the alloy less likely to rust. Stainless steel must be allowed to breathe for this process to occur. Salt attacks chromium oxide, reducing the ability of stainless steel to naturally resist oxidation and corrosion. Regular washdowns and waxing on a schedule will even up the odds.