RS at work wrote:

I finally tried electrolytic de-rusting and I like it. I tried it on
a sheet metal blower housing off a lawn mower and I was really
impressed with the results. The pitted areas of the metal were
blasted completely free of rust and the process removed most of the
paint as well.

The downside is that I now have a dead Harbor Freight battery
charger. I found a 24 V forklift battery charger that runs on 220 or
440 and will deliver 12.5/25 amps. the guy wants $20 so this might be
a good deal.

If it actually works, then yes, it's a hell of a deal. (i.e., good.) :-)

Is this a good candidate for making a dedicated power supply for an
electrolytic de-rusting set up?

Yes, as long as you have control over the current delivered.

I know that a cheapy little battery charger will work but I assume
that the forklift charger has much heavier internal components so it
should last.

Agreed.

I also understand that the power requirements to de-rust vary
depending on the surface area and the conductivity of the solution.
Would it be easy to tweak this charger to make it so I could dial in
an optimal setting?

Only the seller can tell you that.

Also, what sort of fuse or other safety should I be sure to build into
the supply?

If it isn't already fused, breakered, or current limited, I'd say based
on the 25 Amp spec, a 30A slow-blow should be fine. When I worked for
the battery charger manufacturer a few years ago, they used fusible link
wire. :-)

Have Fun!
Rich