Tank Rust Removal

[txironhead]

Go to Home Depot, Lowe's, or Walmart and pick up some concrete etcher. It's phosphoric acid which is what Kreem and Por-15 both use to remove and convert rust. It's safe for sound metal and only treats the rust. Dilute it with about 3 or 4 parts water and let it sit in the tank for about 20-30 minutes. Follow with a good water rinse then blow dry the inside of the tank. If you're not going to fill it right away mix a little motor oil with some naptha and coat the inside of the tank with it. Drain the solution and when the naptha evaporates a light coat of oil witll be left behind. The phosphoric acid doesn't seem to hurt the paint if a little seeps out of the tank.

Oh, how I wish this were true.....

I've been to all three places and guess what? All of the concrete etcher is now "environmentally friendly, organic-based compound" with absolutely NO phosphoric acid. At least that's the way it is in Brazoria and Harris (read: Houston area) Counties. Even a trip to the paint shop yielded no results, as well as calls to several industrial supply shops, plumbing shops and industrial cleaning companies. The strongest stuff I could find was OSPHO, which will work as long as you're willing to slosh it around a lot with a double handful of bolts (never thought of the chain idea, gotta give that a try someday).

However, a friend told me that I could get phosphoric acid, in liquid or powder(?) form, from swimming pool supply companies.

After all of this hassle, I think I'm just going to order the POR-15 kit. I've had great success with several of their other products, and I might just get the automotive kit so I can do the GS and the Shadow at the same time.

[Billy Ricks]

I used POR-15 in my tank to eliminate the fine rust that invariably forms and makes its way into the carb bowls. It turned out great and for about $40 shipped it's a bargain.

[N56629]

The availability of phosphoric acid for etching concrete must be a local thing. I found it and muriatic acid to be available everywhere around here.

FWIW, naval jelley is phosphoric acid. It just comes in a gel form. I'm sure it could be thinned out if one desires. It is also less than half the price of a gallon of concrete etcher.

[gsgeezer]

Any radiator shop can blast the inside and coat it with baked on expoxy.
My GS tank was done for about $50.

[Nessism]

Try removing the rust first with the phosphoric acid solution first before using the Por-15 coating stuff. Most likely you don't need the sealer. Enviro-Rust is good stuff and will eat the rust away. You are going to have to turn the tank quite a few times though and shake it up. Don't be in a hurry and it will work. Turn the tank every once in a while and leave it until the rust is gone - might take a couple of days.