[TheForge] post sand blasting

[Mike Spencer]

> what about washing it with Phospho right away, would that help?  

That's what I would try.

> I'm not really sure what the phosphoric acid preps actually DO on
> clean metal, obviously they neutralize oxides, but do they stabilize
> steel surfaces that DON'T have oxides on them?

Allegedly, a tightly adhering coat of iron phosphate is formed that
is to some degree water resistant and rust-preventing.

I had a sterling example.  After attending a workshop by Chris Ray
where we learned to do repousse and raising over stakes, I did a bunch
or practice pieces, trying out various ideas I had.  One of these was
kinda pretty so I pickled it clean in phosphoric acid and just wiped
it down instead of rinsing.

Fast forward 10 years. That practice piece along with the others have
been sitting on a shelf in my (mostly) unheated shop a few feet from
the ocean.  All the others have a heavy orange-ish fur of rust fuzz,
much more than could be removed with a little steel wool.  That
phosphated piece is just the way it was when I put it there, grey and
unblemished. 

Fats forward another 10 years.  All the pieces are very rusty.  The
phosphated one has a few little brown spots and a couple of brownish
blotches -- possible where I left occasional finger prints on it over
the years.

Caveat: This was accidental success.  It takes some experimenting
to get the phosphate just right -- temp, acid concentration etc.  I
don't seem to have figured out just *exactly* how to get reproducible
results every time. YMMV, WYSIWYG etc. etc.

FWIW,
- Mike