[TheForge] Stainless contamination

[debmiller at fuse.net]

James,
Sounds like good info!!
Thanks
Ray

---- James Binnion <jbin at well.com> wrote: 
> 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
> 
> 
> 
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