Might as well get it sand blasted. There are ag shops that have people doing large equipment all the time. Get the whole thing blasted, then you can see if "surface" rust is really surface. Not that expensive, especially with the results you will get. Make a decision based on results. If all is fine a quick pickling will go a long way. Best primer step for iron / steel is to hit is with phosphoric acid. The result is black iron phosphate which is a dandy anti rust layer and makes a perfect paint surface. Check it out on wikipedia. There are several ways of doing the pickling, including spraying with diluted phosphoric, using "navy jelly" or some variant of that. After the metal turns gray / black, a quick wash with water will get rid of the acid and away you go. So, blast, pickle, wash and paint....


trafdlo