[TheForge] Stainless contamination

[Doug Ayen]

Thus Spake James Binnion (jbin at well.com):
> It is the presence of chromium oxide that is formed on the surface of  
> stainless steel that makes it "stainless"  Other alloying components  
> will help in very crrosive environments but the most important one is  
> the chromium.  If you weld, grind wire brush or polish with an  
> abrasive you end up disturbing the chromium oxide layer and you then  
> need to passivate it to restore the "stainless" qualities. This is  
> typically done with a mineral acid (nitric acid is typical) that  
> dissolves the iron from the surface of the stainless and leaves  
> behind a chromium oxide or chromium  surface that rapidly oxidizes  
> and makes the surface "stainless"  again. If your bar top was wire  
> brushed or polished and then plastic sealed without passivating then  
> you will see the rust on the surface as the iron is oxidized. There  
> are citric acid based passivation solutions out there like CitriSurf  
> that are a lot safer to use than the nitric acid based ones. If you  
> weld, grind, wire brush etc  most stainless alloys you need to  
> passivate it before exposing it to corrosive environments like the  
> outdoors.
> 
> 
> James Binnion
> jbin at well.com

Would it be worth it to passivate stainless steel knives? Sure, as soon
as you sharpen it the edge will lose the passivation, but might it help
keep the rest of the blade shiny?

--doug