Phosphoric acid wash for mildly rusty tank?

[Billy Ricks]

I worked in a factory that made oil seals. The metal portion is stamped, and comes out of the stamping press covered with oil. The oil was removed in a bath with hot - almost boiling - lye. Parts were then dipped in a solution with phosphoric acid and some other chemicals. This removed rust and left a calcium phosphate coating, which would protect the parts from rust for a vew days, in dry weather. Then parts were dipped into an adhesive to seal the phosphate and to improve adhesion to the rubber that formed the seal. I learned that most stamped parts that will be painted are phosphate coated to help paint stick.

Phosphoric acid will indeed remove rust. It will also make the metal rust very quickly. If you remove rust this way, be prepared to paint the part or otherwise coat it almost immediately.

After using the phosphoric acid I rinsed and dried thoroughly. Since I wasn't going to refill with gas right away I made a mix of naptha and motor oil to coat the inside of the tank. Once the naptha evporates a light coat of oil is left behind to protect against rust.

[J_C]

Good info guys! I'll have to try the naptha/oil trick!