Tank Prep and Sealer

[Vincenthdfan]

I can attest to what Marty says. I have experienced one of the few Caswell liner failures I’ve ever heard of. The tank was already professionally lined when I bought it. So not sure what the reasoning behind the decision for it was. Under the failed portion of the liner the tank is smooth and like new. When I reached out to Caswell about it, they told me the same thing that Marty stated. Their product is designed to bite onto rough/rusty and textured surfaces. Very frustrating as the only way to remove the liner is nasty chemicals that they dont sell to the public consumer.

They do sell their remover now to the general public...

 

[Jim]

they told me the same thing that Marty stated. Their product is designed to bite onto rough/rusty and textured surfaces.

I've read that on their website. I say *cough*bullshit*cough*. If all you need to do to rust is epoxy over it, why do restorers tear cars and bikes apart to sandblast/grind/acid treat rust? Short answer is rust continues to...um... rust. Unless it's removed or chemically treated, rust don't quit. They say the more rust, the better. Again, *cough*bullshit*cough*.

Did they happen to mention how to prep a de-rusted tank for their liner to cling better...etching, etc?

I have a tank in mind to Caswell, but its already been evaporusted, only to find seam leaks after the fact (dang it!).

So its smooth inside...no bueno according to Caswell?

I'd do an acid etch. Hydrochloric acid followed by phosphoric acid. That should give plenty of "teeth" for the epoxy to grab onto.

EDIT: this is all my opinion of course...

 

[jetmechmarty]

Did they happen to mention how to prep a de-rusted tank for their liner to cling better...etching, etc?

I have a tank in mind to Caswell, but its already been evaporusted, only to find seam leaks after the fact (dang it!).

So its smooth inside...no bueno according to Caswell?

I have lined two tanks with Caswell. Both were applied to spotless clean metal. One was done about 12 years ago. It went into service spring of 2023. To my recollection, there was nothing in the literature instructing me to apply it directly to a rusty tank. I don’t think there was anything about prepping the metal either way. I’m not really too concerned about it. @willis is the only Caswell disaster I’ve ever heard of, other than someone who had issue in the application.

 

[Jim]

I have lined two tanks with Caswell. Both were applied to spotless clean metal. One was done about 12 years ago. It went into service spring of 2023. To my recollection, there was nothing in the literature instructing me to apply it directly to a rusty tank. I don’t think there was anything about prepping the metal either way. I’m not really too concerned about it. @willis is the only Caswell disaster I’ve ever heard of, other than someone who had issue in the application.

Caswell's website....

https://caswellplating.com/caswell-epoxy-gas-tank-sealer-car-tanks-up-to-20-gal-1-quart.html

 

[Vincenthdfan]

I've read that on their website. I say *cough*bullshit*cough*. If all you need to do to rust is epoxy over it, why do restorers tear cars and bikes apart to sandblast/grind/acid treat rust? Short answer is rust continues to...um... rust. Unless it's removed or chemically treated, rust don't quit. They say the more rust, the better. Again, *cough*bullshit*cough*.



I'd do an acid etch. Hydrochloric acid followed by phosphoric acid. That should give plenty of "teeth" for the epoxy to grab onto.

EDIT: this is all my opinion of course...

The acid etch was my thought also...except, the paint on the tank is flawless.

Damn, I absolutely hate the thought of harming that exterior finish.

 

[Jim]

The acid etch was my thought also...except, the paint on the tank is flawless.

Damn, I absolutely hate the thought of harming that exterior finish.

I'd stay away from the hydrochloric acid then. It finds the slightest scratch in the paint and it'll get under it and start lifting the paint.

 

[Vincenthdfan]

I'd stay away from the hydrochloric acid then. It finds the slightest scratch in the paint and it'll get under it and start lifting the paint.

I may have to settle for tossing a butt load of drywall screws in there and vigorous shaking to try scratching the interior up some?

Not sure if that would work though, I've never even done that for rust removal before, always had good luck with just soaking & periodically shaking either vinegar or evaporust....never saw the need for the screws before.

 

[jetmechmarty]

I may have to settle for tossing a butt load of drywall screws in there and vigorous shaking to try scratching the interior up some?

Not sure if that would work though, I've never even done that for rust removal before, always had good luck with just soaking & periodically shaking either vinegar or evaporust....never saw the need for the screws before.

Have a look at this thread from some time ago. I had a liner failure after I had the tank painted.
https://xs650temp.proboards.com/thread/17274/failed-tank-liner
From that thread:

I removed all of the rust with diluted phosphoric acid. It worked the charm. The Caswell liner is in there now and looks like a coat of glass. I hope it works because there will be no removing it.

That tank is just fine today.