> >Phosphoric acid is the first choice for this, but hydrochloric works,too.
> >Paint shops sell hydrochloric labeled as muriatic acid, used to etch
> >masonry before painting. Phosphoric acid can be found as a paint prep. or
> >sold under the trade name "Naval Jelly" here in the States.
>
> Thanks very much indeed. Do these acids not react with the steel as
> well?
Phosphoric acid reacts very slowly with the base steel, it won't do any
damage as long as it's removed in a reasonable length of time (a day or so).
Hydrochloric attacks a bit faster, but still within reason. In both cases
you have to be very sure to get all the acid off.
> >
> >There are some paints and coatings that complex and neutralize the rust,
> >preventing the spread of it. Loctite sells a material called
> "Extend" which
> >is very effective. I think POR15 does this, too.
>
> Yes, I have come across these, and they are very useful for areas which
> are out of sight; less so for external bodywork, as they tend to leave a
> rough surface that has to be sanded or ground down.
The reason for this is that the original surface is now rough. Not much can
be done about that, the original metal is no longer there and even if you
could turn the rust back to metal, it would still be rough. But a
high-build primer will usually smooth out all but the worst pits.
For smaller parts, you could also investigate
http://users.interconnect.net/nlindsey/rusty2l/electrolysis/electrolysis.htm
Haven't tried it myself, but I'm told it works by others who have.
Randall
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