Has Anyone Stripped and Repainted Steel Tanks?

[MilitantMedic]

I believe 300F condems a tank....not 100% sure though.

According to ZRC and FredT the ZRC CG can be topcoated. We'll just have to see though.

 

[fishoutawater]

Maybe the ZRC is a different formulation. If I try to topcoat the stuff I use, paint beads up like water on a fresh waxed car.

 

[MilitantMedic]

Did you give it a good scrub down with a mild soap?? Might still have a "extra" coating, like aerosol residue.

 

[Jim Lapenta]

I gotta interject here. Laughintom did say his tank has surface rust, so I can assume his is a steel tank. The wire wheel and cold galvanizing would be great for that, but I'm worried someone with an aluminum tank would try the same method.
Do NOT use a steel wire brush on an aluminum tank. Traces of the steel wire brush will become imbedded in the surface of the aluminum. This will cause galvanic corrosion, which is caused by placing dissimilar metals together. An electrical current is induced between the steel traces and the aluminum, and will corrode no matter what you paint it with. Same for the cold galvanizing compound. Although next to each other on the galvanic scale, zinc, like steel, will react with the aluminum and eventually cause corrosion, especially in salt water.
(I'm an Inspector on fighter jets. They drilled this into my head years ago)

And Militantmedic,
I've had trouble getting paint to stick to cold galvanizing coated parts. I also build custom cars. I only use CG on hidden undercarriage parts and between welded seams.
It's pretty tough stuff by itself though, and would look good on a tank.

But if you have an aluminum tank that needs refinishing, use only aluminum oxide blast media or paper (no wire brushes or steel wool). Then paint it with epoxy primer and epoxy paint.

Jimlap, you can't powdercoat aluminum? I know how hot powdercoating is, but aluminum doesn't melt before about 1400 deg. (Might weaken it though) But if it won't hurt the tank, it sure seems like it would be the way to go. Very tough stuff.

I did not say you could not powder coat aluminum. We do it all the time. You cannot however subject an aluminum TANK to the 375-400 degree temperatures that standard powder coating requires. It is not just heating the paint up to 400 degrees. The base metal must reach that temp for proper curing to take place.something as thick as a tank may require 20-30 min or more at that temp. I see 1/4 inch al warp all the time from 8 min at that temp. I don't know about you all but I learned in my ow course that a tank subjected to more than 180 degrees must be condemned. There are uv powder coatings that require no heat only uv light. I personally have no experience with these so don't know how tough they are. They are used for coating wood and plastic.

 

[MilitantMedic]

I don't think 180 is accurate, becuase if you leave a tank (AL) out in the sun it will reach 180 no prob. I've seen quite a few tanks blow their discs in the sun, sorry to lazy to do the math to figure out what temp. it would take to make a 3100 psi tank pop off. Those tanks are usally black, however I would highly doubt that they fail hydro or get automatically comdemed.

 

[Spoon]

wow never knew that there were so many possibilities. always thought it was a no brainer. il just let the pros take care of that for me and save me the headaches

 

[dmdalton]

300 degrees is the not to exceed point for aluminum cylinders (6351 & 6061). Consequently no powercoating or heat cured painting.

While tanks get hot in the sun, I would be surprised if they will reach 180. I did the math on the gas expansion and tanks in the hot trunk of a car reaching 130 or so would not be cause enough expanison to burst a disc that is right for the tank (test pressure +/- 10% which would be 5000 psi for an AL 80).

Galvanizing is very hard to paint. Let it weather for a while outside or coat it with vinegar and let it sit for a while. Should help. Or just forget about the painting. the ZRC will serve as a fine topcoat.

Dave D

 

[MilitantMedic]

I've seen 3 tanks blow their discs while being left in the sun. Still trying to figure out how they would pop off.

 

[MilitantMedic]

OK some further reading shows (according to Vance Harlow)...

Burst Disc Pressure @ 4200psi
Alu Cyl. Condemnation @ 350F

Doing some more math I get burst discs going around 200F, for "hot fills." I've had a fill @3800psi @ ambient temp. so who knows.

 

[dmdalton]

OK some further reading shows (according to Vance Harlow)...

Burst Disc Pressure @ 4200psi
Alu Cyl. Condemnation @ 350F

Doing some more math I get burst discs going around 200F, for "hot fills." I've had a fill @3800psi @ ambient temp. so who knows.

Last I've seen from DOT on burst disks was hydro test pressure +/- 10%. Every AL 80 I've seen (3000 psi working pressure 5000 psi test pressure) has a 5000 psi burst disk in it.

4200 would be about right for a LP steel.

You've gotten 3800 fills on AL 80's or on a LP steel? If on a low pressure steel with the original burst disc (4200 psi or so) you could indeed have a failure.

Dave D