Tank Cleaning: Phosphoric Acid vs. Rubber

[Tracer]

Will the rubber gasket/seal used on the sending unit in the tank hold up against the acid treatment I'm going to put in the tank?

I've fabricated from sheet metal a cover for the sending unit hole, and I'm using the sending unit's rubber gasket while I swish some diesel and chains around inside the tank.

I'm curious if I can use this rubber gasket when I do the acid treatment to the tank next.

Thanks a heap!

[almarconi]

Don't use the gasket from the sending unit, use some rtv gasket maker (between the tank and sheet metal cover) or go to home depot and get a small piece of rubber sheet (usually available in the plumbing dept).
You could also use a piece of rubber from an old inner tube. When you are soaking the tank, put the tank in a large plastic tub so if any acid leaks it won't do any damage.

[almarconi]

To answer your question butyl rubber, natural rubber, neoprene, nitrile rubber, polyethylene and polyvinyl chloride all have good chemical resistance to 70% phosphoric acid. For our applications the concentrations are substantially weaker so all the above material would be suitable. I still would make my own gasket out of a scrap piece of rubber.

[J_C]

Are you talking about the rubber gasket that is glued to the tank? If so, mine held up fine with a 50-50 phosphoric acid and water solution. I used a sheet metal cover as you mentioned.

[duaneage]

Watch the paint, don't worry about the rubber.

[bwringer]

Why is anyone still using phosphoric acid?

I've used Evapo-Rust on a lot of rusty parts, and it actually works a lot better than phosphoric acid ever did. You can also leave your part in the Evapo-Rust as long as you like -- it won't harm sound metal.

This stuff is pretty much harmless to anything except rust -- you don't need rubber gloves or a hazmat suit. It even smells nice.

http://www.evapo-rust.com/

I've tried using phosphoric acid and its variations (naval jelly, etc.) many times, and it never seems to do a complete job. And then you have a hazardous acid to deal with.

[ktp1598]

Damn! Time to go get some!

[Tracer]

Bwinger,

For the inside of a gas tank, would I fill the whole tank with the stuff?

And then to prevent flash rust, would I lightly coat the inside with the evapo-rust and let air dry?

At least that's what I'm thinking after looking over their website.

Finally, it sounds as though I can flush it down the toilet when done.

Thanks for the tip.