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Discussion Starter #1
I'm about to have my gas tank painted and I'm going back and forth on whether I should seal it with Caswell or Red-Kote, or just keep the tank full of gas all the time.

I de-rusted the tank a couple months back with Phosphoric Acid. After drying it I immediately sprayed it with WD-40 and poured in a bottle of 2-stroke oil. For the first couple weeks no rust formed as long as I rotated the tank every couple days. But then I had to drop the tank off with a friend to finish some metal fabrication on it and when I got the tank back it was all rusted out inside again.

So now I'm wondering if I should:

a. De-rust, then seal it with Caswell before giving it to the painter or
b. give it to the painter and attempt to de-rust it afterwards (with the fear of potentially messing up my new paint), and then just keep the tank full of gas all the time.


I was leaning towards sealing it, but I'm also worried about the longevity of the sealer. I've heard when it comes apart its a real PITA to remove.

Thoughts? Experiences?
 

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I vote for not coating it especially since it seems to be relatively clean. I don't trust any of the pour in tank linings personally, would rather deal with a little rust.
 

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Well I had a very rusted tank. The bike had been left with gas in the tank in 1993. I got the bike in 2014. The tank was mess with rust and varnish. I used the POR15 motorcycle tank treatment kit, and followed directions. That was four years ago and the coating is still in perfect condition. The bike is stored with the tank empty each winter. No rust, or no coating failure.
I would not hesitate to coat a tank. POR-15 system is by far the best way to go.
 

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I removed the rust from my gas tank and it was very easy by using a product cal "Evapo-Rust", it so easy I will never seal another tank. The tank I did seal rusted and it very difficult to remove the sealant crap. Do not seal the tank! Ever.
 

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I discovered blisters in the paint on my GL500 in 2003 and when I pierced one it bled gas. I sanded it off in the blistered area and discovered that it had rusted out from the inside. ("Rusted out" very specifically means that the rust has made a hole in the metal. Something with "flash" or surface rust is not rusted out.) I made a few calls and took it to a rad repair place where they soldered up the biggest of the holes and "lined" it for about the price of a POR kit to do it myself. That tank was on the 500 for a couple more years and has been on my CX650E based machine since 2006. 15 years later there is no sign of the coating coming off or the leaks coming back.

I was warned that they could not guarantee that the tape used to seal the openings when they worked on it wouldn't damage the paint and I did have to touch up at least one place (but I had to work on the area where the holes are anyway) so if you are going to coat it, before painting would be the best bet.

BUT I would be asking why it is rusting. What did you do between pouring out the acid and pouring in the oil? If you just drained the acid and added the oil, the acid would still be on the surface of the metal so any time it is exposed to air it will start to corrode. Ideally, immediately after removing the acid you would have flushed the tank by filling it with clean water several times to remove all traces of the acid and then added a litre or so of a solvent like lacquer thinner or gasoline and shaken it around (repeat several times) to flush the water out.

BTW: Why did you use both WD40 and 2 stroke oil?
 

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Denatured alcohol or Acetone will absorb any water. Acetone will destroy any paint as well... Caswell's Epoxy system or POR15 if you follow their directions to the letter and dry the tank so it is bone dry before coating. If you have rust in the seam it is very difficult to stop that and rust expands steel to 10x its size and it absorbs and holds water. If your seams are rusting, it is probably too late as it is nearly impossible to stop. You are talking about flash rusting but with the tank coated in 2 stroke something else is going on as a phosphoric acid treatment should have left you with a phosphate coating on any rusty areas.

A hair dryer or heat gun into the tank neck for about an 30 min to an hour should dry the tank.

Definitely line before any paintwork and plan on paint. If you friend had to do any welding or soldering he had to get rid of your oil because it would contaminate a solder or braze/welding...
 
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Discussion Starter #9
RAFster122s are you suggesting that i scrap the tank if the seams are rusting?

I just gave the tank another quick phosphoric acid treatment and noticed there is a leak from one of the seams. I dropped it off at a radiator shop to have them check it out and see if it can be soldered, and pressure-test it. Then my gameplan was going to be to seal it with Caswell before having it painted. This is all assuming the rad shop thinks its fixable.
 

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IF there is any chance of rust in the seam and we are not talking about started but it is starting to expand, then you are not going to get it to dry the rusted area. POR will trap the water and its sin is that it will do that...it then rusts even faster if it is ANYTHING like their rust paint. You can't just metal ready it (phosphoric acid wash) it and then rinse with water and dry it with an acetone wash and then dry the tank...it simply will not dry that rusty seam.
If it is deep in the seam then it is a bandaid to line it, you need to go ahead and line it and start looking for a new tank.
Want to see something interesting. Use paint stripper on a rusty area and see if you do not see little lines of rust branching out like capillary tubes away from that rusty spot. That is why rust is hard to eliminate.
My honest opinon
 

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You ment to say POR 15 didn't you. POR has a kit that includes a cleaner, rust converter and sealer.

The cleaner may be the most important part. I cleaned my tank with simple green and very hot and a power washer. I was sure it was clean. Since the POR kit came with a tank cleaner I used it. Boy was I suprized. The crap that came out of my clean tank was shocking. It was brown crud. I suppose varnish and rust that simple green did it not dissolve.

Converting the rust just eats away more of your tank each time. My experience is POR works, but you have to follow directions to the letter. POR is a moisture cured product. If the tank has moisture in it the final coating will fail. If it is to humid on the day to do the job the coating will fail. If you don't rotate and drain the excess the coating will fail. If you can read and follow directions the product will preform as described. If you like short cuts forgetaboutit.
 

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Phosphoric acid products like fertan convert and stabilise the rust without removing any of it.

I treated my 500Cs tank about 9 years ago. This was done due to a small pull on the spotweld on the front tank mount having caused a pinhole leak.

I used a caustic salt type degreaser to clean, fertan to treat and acetone to dry. And much rolling with chains with bolts through them.

That tank is still good.
 
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