[TheForge] Electrolytic Stainless steel passivation

[Cameron Stoker]

Hi all, and big thanks to Frederick,
     I have a project coming up where I will try this process to =
passivate=20
some ss that will get plastered in place. I was wondering if anyone else=20=

had tried it, and how the surface finish is effected. These are some=20
pieces which will be finished with 120grit flap discs before the electro=20=

process. I am imagining that this will dull the finish a bit.
    I should probably go experiment, but if someone already has I'd be=20=

excited to hear about it.



On Wednesday, August 8, 2001, at 04:41 AM, Frederick Faller wrote:

> For all of you guys who know that knowing why can lead
> to innnovation:
>
> I was asked by my brother to make a custom gaff for
> his fishing passions. He wondered if I could forge it
> out of stainless. I said I could, but, being the sort
> of "do it all myself" kind of guy, I was wondering how
> on earth I would get it passivated without paying
> through the nose or paying at all.
>
> So I looked up passivation (which I use all the time
> at work making medical instruments, but had always had
> other vendors do it) Passivation of stainless pieces
> is necessary if you want to make them truly stainless,
> so if you are forging stainless stuff and are not
> passivating it, you and your customers may be
> disappointed.
>
> Even the best stainless steels still have free iron in
> them. When a stainless piece is machined or forged,
> some of that free iron resides on the surface and will
> rust. Passivation is the process of removing the free
> iron, leaving the manganese, chromium etc. on the
> surface of the piece. This is why if you scratch
> stainless deeply, the scratch will rust.
>
> Well, wouldn't you know, all they do to passivate the
> SS is put it in an electrolyte and run the current so
> that the free iron is removed from the surface!
>
> So . . . all you guys with electrolytic rust removal
> tanks, here's how you can passivate stainless at home:
>
> Put the positive electrode on the piece you want to
> passivate (this is the opposite of the rust removal
> process) and the negative on another chunk of iron in
> the solution. Turn on the charger and the solution
> immediately attacks the SS piece, but can only remove
> the free iron. Leave it for a few hours and then wash
> it off. Now it will not rust.
>
> BTW, this explains why SS electrodes used in the Rust
> removal process last so long. They are just
> passivating and it takes a long time to remove all the
> free iron behind the alloy barrier that is left.
>
> Cool Eh?
>
> Frederick Faller
                                      Cameron Stoker
    				"May you run like a vicu=F1a!"
                                      cameron@stoker.net