My propane tank was rusty and needed a refinish. No one in my area would touch it as far as sandblasting or painting it, so I took on the project rather than spending $1500 on a new tank. I will post links to some of the useful things I used. I spent a lot of time considering different options and methods for restoring the tank. I considered using a rust converter, rust remover, sanding and grinding options. I also considered leaving the intact paint as is and just addressing the rusty areas. In the end after lots of trial and error, the best solution by far was using an abrasive wheel from harbor freight.
The wheel was made of a very tough plastic attached to my angle grinder. This did, by far, the best at removing rust and paint but not removing good metal. Prior to this, I tried scraping the rust, then I tried sanding with an orbital sander. These did very little. I also tried a pneumatic scaler. This was actually pretty good at removing the layers of scale rust from the tank, but it leaves behind rusty metal. On a separate note, I refinished my house battery cages for the batteries under the van and the scaler was great at this.
I decided that I would rather get the tank down to bare metal rather than try to use a rust converter. I felt that this would be the best option for longevity of the finish. Once I had the vast majority of the rust off I washed the surface with a degreaser and dried it off with a heat gun and then wiped the surface down with acetone. Once this was finished, I immediately put a couple of coats of Rustoleum clean metal primer (for bare, painted or lightly rusted metal) and let it dry overnight. Then I began top coating with Rustoleum Stops Rust Satin Protective Enamel. In my research, these seemed to be the best options for my situation.
Put on 2 light coats a few minutes apart on the top 3/4 of the tank and let it dry for a week to let the paint cure. I then turned it over and painted the bottom 1/4 with 2 light coats. I repeated this process 4 times so that the tank has 8 total coats and always allowed time for the paint to cure between coats. This process worked very well and I did not have any problems at all with coverage, adhesion or quality of finish. It took a very long time to do the painting (about a month because of the dry times. I had no problem with the tank laying on the finished side and damaging the surface because I allowed the cure time. If I had a way to hang the tank, I would have been able to shorten the painting time dramatically.
I installed the tank this weekend. It is a very tight squeeze to get the tank back in but managed it with the help of a floor jack rigged with a board with edge strips to keep the tank from rolling off. I probably have 20 hours into the tank restoration. If I knew at the start what I know now I could have it done in half the time easily. There was a lot of trial and error in my process. I hope this helps someone else shorten the learning curve of restoring a SMB propane tank.
Wheel for removing paint and rust: https://www.harborfreight.com/4-1-2-...eel-94017.html
Scaler for removing rust: https://www.harborfreight.com/compac...ler-96997.html
Before, during and after pictures: