The Stovebolt Site Forums The Shop Area Paint and Body Shop Gas Tank Sealer

Hey guys,

I originally posted this in the Engine and Driveline Forum, but I think it fits better here.

I'm planning on using electrolysis to get the rust out of my gas tank. The idea is to use a piece of rebar down inside of the tank as the positive electrode, and the tank itself as the submerging tank & negative electrode. Does anyone have any suggestions on a good gas tank coating/sealer to prevent it from coming back?

Some I've seen (including Redkote, Kreem) contain Methyl Ethyl Ketone and seem to me to be inferior, but the products from KBS Coatings and POR 15 don't. POR 15 I know is a Isocyanate Prepolymer which I think is similiar to superglue. Does anyone know what the difference is? Or better yet, Which is better?

Right now I'm leaning toward KBS Coatings

I used the Por15 kit on my 37 pickup almost 9 years ago and it still looks great inside. The kit also comes with stuff to do the outside to. I plan to use it on my panel tank. I have NOT used the others so I can't speak for them but I am happy with the POR15 and so are quite a few others I've talked to.

Inferior???? I used Redkote and am quite pleased with it's performance. It's rock hard while remaining flexible and it did a great job of plugging several pinholes. It's been three years since I put it in my 38's tank and no issues with it at all.

Hi Bryan, I had a crazy thought. Why not submerge the whole tank in vinegar to clean it? After reading the tech tip on this method recently. I built a wooden box to be used as a vat,laid heavy duty plastic to hold vinegar. The box is built somewhat larger than the pcs. Then I use deviders to make the area smaller to accomodate smaller pieces & only fill in the vinegar as required. I am very impressed with the job that this is doing. After about 7 days, when it comes out I pressure wash & clean off the rust just like cleaning off mud. It removes all the rust & leaves only the good metal. Wipe it down & use a heat gun to dry it good. Sand lightly with 80 grit. Then it can be welded,repaired,sealed or primed. It comes out super clean & gets into every nook & cranny. I think most of it evaporates. I have cleaned many small and some fairly large pcs successively using this method. The results are awsome. I like this method much better than electrolysis. Its cheap, & safe for our enviroment. I had my tank sealed by a local gas tank specialty shop. The cost was very low because it was a clean tank. Just a thought. Hope this can help someone.

Tiny-

I have no idea what Methyl Ethyl Ketone is, but when both KBS and POR 15 touted that their products don't contain it, it made me think that it's somehow an inferior product. Maybe I got roped into some clever marketing.

Vick-

I've used vinegar to de-rust things before. I wasn't all that pleased with the results. One of the problems with vinegar is that it takes a long time, and it's just an acid, and it will eat away at rust and metal alike (obviously rust faster, but still....) Plus I've dumped out vinegar on my lawn before and it killed it. For electrolysis as long as you don't use a stainless steel positive electrode, all you end up with is iron-rich water.


I'd love to hear from someone who has used the KBS product!!!

THANKS FOR ALL THE ADVICE GUYS, KEEP IT COMING!!

MEK is a polymerizing catalyst, as used in fiberglasing, and the marketing ploy is they're playing on folks fear of the chemical - in concentration under the right circumstances it can be explosive .... but then so can gasoline ... just means after application don't try peering into the tank using a match for light

yes, vinegar is a good weed killer, in concentration - not real useful for rust removal cuz as Bryan sez, it dissolves good metal as well as bad .... if used make sure you don't splash any on concrete, it dissolves the lime in cement and etchs the surface - also the fumes can be corrosive to other metal objects nearby, use out in the open air .... it's a good 'priming' pre-treatment for galvanized metal to let paint stick, but even better for soaking your tired feet, keeps foot fungus under control electrolysis is way better and very benign

Bill [the vinegar maker]

Bryan, my concern with this method is that electrolysis splits the water to hydrogen & oxygen(2 parts hydrogen, 1 part oxygen) I have read that hydrogen gas is very light and will rise and stay in the ceiling area of a room. Remember the Hindenburgh!!
But at the same time there are many good articles that have been written on the safety precautions & very fine results of this method. It sounds like you have done some research. Just like to be safe and help others with the danger of it. The vinegar for me is just a safer personal choice.

Note that whatever you try will cause any rusty spots to get very thin or even leak. I did a motorcycle tank about 5 years ago with POR-15 and it still is holding up, but I made sure I got the entire thing well coated. I must have tumbled that thing over and over for at least an hour, it was tedious. I used phosphoric acid to etch it first. Electrolysis may get rid of most of the rust but it may not provide enough tooth to adhere the coating, at which point the tank is ruined. Make sure to etch the tank with whatever the coating says to use, and follow the instructions to the letter.

I wouldn't do it again unless I had a tank that I couldn't get a reproduction for. The bike tank was one of those.

Just pulled the tank the other day, and looked inside (not with a match for light, mind you). I didn't think it would be possible, but the inside of the tank was rustier than the outside of my truck! I just hope that when I do the elcetrolysis, that I don't spring a leak!!! For clarification, the KBS Coatings kit I'm planning on using has de-rusting, and surface prep stuff included in the kit. The electrolysis is going to be used just to get the worst of the rust out.

Update:

I've had the electrolysis running on the tank for about a week now. I'm using a 12-volt 6-amp battery charger. I've dumped the solution and replaced it twice now, I've also tried shaking pea gravel around inside of it, to knock some of the loose stuff off. So far so good, it's taking a little longer than I thought, but there's alot of surface area to de-rust. My cathode is a piece of 3/4" metal strap that has been eroded to about half of it's original thickness, and is VERY brittle due to the hydrogen embrittlement. I've peered down inside of it with a flashlight, and there are patches of bright shiny metal!! More to come!


By the Way...I've heard that using a diluted mixture of hydrochloric acid after the electrolysis process will help to remove the black crud that the electrolysis leaves behind. Is this true? Is there anything else that will do that?

if there's real 'crud' a good rinse will get rid of it [if it's impacted, use a high pressure hose], if you mean the black surface, that's the color of the converted metal and it won't change, the previously rusted areas won't get looking like "new" again, which is why afterward you need to use the sealer/sloshing compound, same as you'd have to use primer and paint on body panels - if you try to get it all perfectly clean you'll wind up eating the metal away like your electrode

also you shouldn't need to replace the solution, just settle out the particulate and re-use it, it's effective almost indefinitely

Bill

I checked the tank the other day, and I was really impressed! All the rust is gone! Now I need to get the black stuff out. Normally this stuff can be easily scrubbed off whatever is being de-rusted, but I can't reach inside the tank. I've tried tumbling pea gravel around inside, but it doesn't work so well...

CAN ANYONE RECOMMEND AN ACID OR CHEMICAL THAT WILL DISSOLVE THE BLACK STUFF LEFT BEHIND BY THE ELECTROLYSIS PROCESS, WITHOUT EATING AWAY THE METAL TOO BADLY???

Thanks guys, I promise to post some pictures when I get this done with.