Ron Nielson wrote:
Wash them with a stiff brush. Let dry. Apply OSPHO rust converter/metal primer with a spray bottle. OSPHO RUST CONVERTER Make sure you use goggles for eye protection. After it dries, spray with rust resistant paint. Should never have problems again. I did my entire trailer frame with this stuff and it works great.
OSPHO is no longer on the shelf here locally. I got the same stuff in a gallon jug at Home Depot. it is in the paint prep section. Basically all the stuff is a solution of phosphoric acid. it converts the iron oxide (rust) to iron phosphate which is inert.