[TheForge] stainless rust

[James Binnion]

On May 12, 2009, at 9:20 PM, ries wrote:
>
>
> So its my story, and I am sticking to it, that most rust on stainless
> is caused by polluting the surface with mild steel inclusions.

Welding on stainless can also can be a cause of rusting.

>
>
> I know that under normal circumstances, stainless forms a chromium
> oxide layer, which does not rust.
>
> In Seattle, near where I live, there is a large outdoor stainless
> sculpture that was installed in the mid 70's. As far as I know, no
> passivation, no electropolishing, just sanding with a large sanding
> disc on a big 9" grinder. 30 odd years later, in Seattle weather,
> which is wet, to say the least, no rust.


Stainless self passivate when given a chance. As you point out  
contaminating the surface with carbon steel is probably the biggest  
source of rust initiation.



James Binnion
jbin at well.com