I've done a search and read a lot - but it's still fairly ambiguous. I am hoping that, for my own information and others on this site, someone can help me lay out a fool-proof method for dealing with rust. I am currently dealing with some very serious rust on my Ranchero. The easy answer that people will give you is "cut it out and replace the metal" That's great... but we all know that in some circumstances that is not a realistic approach. What I am looking for is some constructive information on dealing with rust in two circumstances. 1.) Surface rust on sheet metal. I sandblasted my fenders down to bare metal, and then primered them with rustoleum. It's been a few months (and it's been out in the weather) and I can already see rust coming up through the primer. Is the rustoleum primer I used not waterproof, or did I just not get all the rust before I painted (altho it sure looked rust-free after blasting). What primer should I use if I figure on it sitting a while before getting to paint? (specific, please) 2.) Cancer. It's a unibody car, and suffers from typical cancer. I am not worried about the structural aspect - I feel comfortable fixing that issue. What I am worried about is stopping the existing rust and keeping the cancer from spreading. Short of cutting it out and using new metal (which is not an option for many parts of it) What approach is best for accomplishing this? And please don't say "use a rust neutralizer". Tell me WHICH neutralizer to use as there are about 200 different ones on the market and I am sure they don't all perform the same. Thank You.