I was studying the effect of time on stainless steel equipment, ranging from kitchen utensils to medical equipment. I wanted to understand which component is responsible for losing shine of instruments
To the best of my knowledge the shine in SS is because of the two things:
(1)presence of Cr. If any thing or event alter the chemical composition at the surface (depleting the Cr content below a desirable limit), the shine will also got affected.
(2) polished surface. If the surface get scratches or become rough the shine will again got affected.
I didn't know much about the household utensils but I know about the metallurgical grade SS steels samples, where one more phenomenon is responsible for the blackening of surface, which is decarburization.
Hi, stainless steel appear "stainless" because of a few nm (Nanometer!) thin passive layer, mostly consisting of chromium oxides / hydroxides. In some cases, the layer may grow thicker or may contain other metal oxides (iron oxides e.g.) and that may also change its color. A common phenomenon in hot waters with low conductivity and oxygen content is rouging. It got its name of the appearance: rouge-like color.
Hope that helps a little? ;-)
Best regards,
Andreas
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