Happy, I may actually be a little helpful on this. Stainless steel is an alloy of steel, and either Nickle Cadmium or both. Different grades of stainless contain different percentages of the other two metals. You also will see it listed as NI-cad steel at some times. The nickel and cadmium, being Non-ferrous, oxidise (tarnish) without a lot of discoloration, and thus the oxide layer is created. Furthermore, as with many alloys, certain metals tend to rise closer to the surface during cooling, so the non-ferrous counterparts in this case tend to be more prevalent at the surface of the stainless steel when it is finished. This oxidation is usually enhanced or created at manufacture. It is extemely easy to oxidize hot metal, and especially molton metals, so once formed, it is only a matter of allowing it to cool in the prescence of oxygen. If the steel is plated. or very low grade scratching it will allow red oxide to form at the scratch. if it is a higher grade of stainless and pure all of the way through, it will seldom rust or visibly tarnish even when scratched. Something you will often notice is dark grey patches on cheaper stainless items. This is the same oxidation that would normally be rust, it is just more controlled and therefore less obvious with stainless. BTW the better the stainless the less attracted it is to a magnet. and also the finer the surface polish of any metal the slower it will oxidise.
Dave
Dave
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) but speaking of citric acid, we get 50lb bags in dry form from a chem. company. At the end of the year, we pour in several pounds into our fiberglass raceways (tanks) to clean the resilient algae that grows into the scratches. Works great! Can't think of anything else, I'm at home doing the "D" w/o a covercharge!