[TheForge] Re: Chemical Questions ?

[Mike Spencer]

Dave wrote:

> I have a couple of old (1930) and very delicate iron panels that need
> refinishing.

What an exciting job!

I had very satisfactory results using glass bead on a set of indoor
gates I made in the early 80s which had been stored in a damp cellar
on a dirt floor for several years.

I used a borrowed, inexpensive sandblast outfit and a tent rigged from
plastic tarps (for media recovery).

Some experimentation with air pressure on a trial piece and then on a
least-exposed area of the real work should make it possible to find a
setting that will remove all the rust with no (or negligible) matting
of the base metal.

I did find, when I came to re-blue and finish in a good light, that a
tiny amount of rust remained in some deeply pitted areas, probably due
to poor visibility through somewhat murky visor rather than failure of
the method.  No rust was left in the hard to get at corners that would
have been difficult to clean up after a chemical treatment (such as
phosphoric acid) and there was, naturally, no problem with residual
water, acid or salts that might have collected in the joints.

The badly corroded and pitted areas came out a bit rough, of
course, but the areas that were lightly rusted looked as good as new
after glass bead, 0000 steel wool, re-blueing and wax.

The only caveat is safety: I was hasty enough [1] to use whatever I
had on hand for protection -- goggles, face shield and wool cap -- and
ended up with a single glass bead in each eye.  Was two weeks before I
got them out.  And they didn't get there while blasting but while I was
washing my hair after work!  Use a proper hood that keeps the stuff
out of your hair as well as your eyes!

- Mike

[1] Omnes festinatio ex parte Diaboli est.
    All haste is of the Devil.

---
Michael Spencer                  Nova Scotia, Canada 
                                 
mspencer@tallships.ca            
http://home.tallships.ca/mspencer/