Muriatic acid is simply an industrial grade of hydrochloric acid, versus reagent
grade. It is an excellent steel cleaner, but treacherous to use on cars. IF it
seeps into seams, you will never get it out, and it will open the seam. Only
use where you have large, open surfaces. Best neutralization is with a baking
soda solution, followed by water. However, this will leave an extremely thin
coat of rust (you see it as a very pale golden-brown colorization.)
Muriatic acid is good primarily only for deep rust. After the deep rust has
been completely removed by the muriatic acid, then neutralize, and follow with
metal-etch solution, which can be purchased from any auto paint supplier. Metal
etch is a phosphoric acid solution that gives the metal a microscopic porous
surface and also is highly stable, and rust resistant. After this, follow with
a high quality primer.
Cheers.
William Hooper wrote:
> Cleaning the interior of the tank with muriatic acid may have contributed to
> the returning rust. You must completely neutralize muriatic acid, or it
> will begin a lifetime project of rusting away whatever steel it has touched.
>
> I once painted a room containing a theater organ blower; the cement surfaces
> had to first be scrubbed with muriatic acid. I scrupulously avoided getting
> the muriatic acid on metal parts such as conduit, disconnects, etc. Even
> after washing these metal surfaces with soap & water, enough of the muriatic
> acid *from the fumes* remained to begin the rusting process through enamel
> paint, galvanized coatings, etc.
>
> Original message follows:
> ------------------------------------------
>
> I recently redid my fuel tank for my 1960 TR-3A. For the inside, I
> blocked off the openings and poured in several rinses of muriatic acid (wear
> proper safety protection). After that, I followed up immediately with
> several rinses with lacquer thinner. If you rinse with water, you get
> immediate rust. After that, I poured in some tank slushing compound that I
> got from MOSS.
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