>
> Resto:
> Homebrew rust remover. I know, gone over before! Greg said it's poss. to
> use vinegar solution over a few weeks, and I've heard of people using coke
>(!).
> It seems the prefered NastyStuff (tm) is phosphoric acid. Do you just
> waltz into your local hardware shop and say "a gallon of your finest
> phosphoric acid my good man....heres a nickel for your trouble"? I'm
> just wondering where to get it....and what strength solution to use,
> AND then how long to leave parts in?
Phosphoric acid isn't THAT nasty. I've gotten tons of it on my skin and
lived to tell about it. Mostly it's just mildly irritating. This is
not to say I don't wash it off ASAP and I don't recommend squirting it
into you eye. But I've never gotten a burn from it.
I don't think you'll have any trouble finding de-rusters with phosphoric
acid in them at your local hardware store. The most popular brand is
probably Navel Jelly. I've seen other brands as well. Metal etched
usually have phosphoric acid in them; I've even have some tile lime
remover that has phosphoric acid in it. And of course auto paint stores
carry various metal preparations that contain phosphoric acid; e.g.,
Metalprep.
There are alternatives to phosphoric acid that work about as well but
they tend to be more expensive and are harder to find. These are
sometimes referred to as oxygen scavengers. I think they are just
organic acids and work on the same principle as phosphoric acid do.
Places like Eastwood and JC Whitney sell them. I found some at a local
Home Depot building supply store once.
As for vinegar, I've also heard that it works. I've tried it and if it
does, it works Veeeery slowly. I experimented with it on some rusted
steel once and after several day couldn't detect any action at all.
I've also used muriatic acid (HCl used in swimming pools). The up side
to this stuff is that it works fast and doesn't leave a residue. Not
leaving a residue is a plus if you plan to solder or weld the de-rusted
area. I use it on my gas tank, for example. But there are some serious
negatives to using muriatic acid: 1) It's a FAR FAR stronger acid than
phosphoric!! 2) It eats metal at about the same rate as it eats rust.
This is okay if the only alternatives is to grind off the rust, but not
generally what you want. 3) The de-rusted area re-rusts almost
instantly because of the Cl (road salt rusting action), so something has
to be done right away to protect the metal. What I've done is to rinse
thoroughly and retreat with phosphoric acid which leave a residue that
gives temporary rust protection. 4) The fumes are very corrosive both
to humans and to any nearby bare metal surfaces. 5) Storage is a pain
because it's far more dangerous than phosphoric acid. The fumes tend to
migrate through the plastic bottles that it's sold in.
Roland Dudley
cobra@cdc.hp.com
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