done the rust conversion coating in the past with marginal results. the rust will eventually reappear (usually 3-6 years). if you want a long term repair, i'd recommend some type of media blast. most importantly be sure to use a catalyzed primer. valspar and/or morton has a product called direct to metal (dtm). if your set on the conversion coating, i'd primer and then fill the pits with a 2 part (catalyzed) spot putty that can be used over primer. the product i use is called half-time. good luck.