[TheForge] last project

[RIES NIEMI]

on 6/5/03 12:03 AM, Paul Hewitt at bugnco@lighthousekeeper.com wrote:

> Ya know it just occurred to me that what your doing isn't really
> electropolish its passivation.  We passivate anything we heat, actually what
> happens when you weld is you burn off some of the nickel and chromium from
> the stainless and float the iron which turns colors to the surface.  Duh
> somedays I should engage the brain.  What was that Dain Bramage.  The answer
> is nitric acid, and electricity.  I have done that but I use a scotch brite
> pad a grey one not a red one.  I have an inverter 300 amp welder that goes
> 0-50 v and 0-300 amps I use it for a power supply to do that but I have
> never used it on a weld per say we have "scrubbed" the inside of finished
> tanks where the weld zone shows through by causing oxidation. Or just plain
> heat marks. Passivation is the removal of iron from the surface to prevent
> discoloration.

I will have to dig out the reference books to check for sure, but as I
understand it electropolishing and passivation are basicly the same thing-
the only difference is the acid, the time in tank, and the shininess of the
result. 
If it comes out gray, its passivated.
If it comes out shiny, its electropolished. Its also passivated too.