On Tue, 05 Apr 2005 13:22:32 +0100, The Natural Philosopher
wrote:

Also good for removing surface rust!

Phosphoric acid probably then.

Phosphoric acid won't remove rust at all. Instead it converts it to
phosphides. If you've already wire brushed it to remove the bulk,
then this might give you a useful surface for painting, but it's
_stabilisation_, rather than removal.

The best acid for careful de-rusting is citric. Sulphamic acid, as
used in most descalers, isn't bad either. Hydrochloric (aka muriatic
or brick acid) is pretty lousy in comparison.

But if you really want to de-rust, use electrolysis. Easy and the
results are vastly better.