Last year I bought some POR-15 to "fix" some minor surface rust on my rear fenders. I only bought the starter kit because there was only a few, very minor rust spots. Followed the directions, removed flaking paint, bubbled spots and sanded. Used the metal prep stuff, let it dry, and then applied the POR-15. Let it dry and then topcoated it with touchup paint. After all of that was done, I put fender flares on the truck to cover up the "not so nice looking" fender. This spring I decided to pull the fender flare off to see how the truck had "weathered" the winter. It didn't fair all that well. The spots that I had uses POR-15 on had bubbled up under the POR-15 and caused more rust. I pressed on one of these bubbles and water squirted out like a blister. Now I need to go back and fix the new rust AND the spots where the POR-15 is. Some of the POR-15 stuck and worked. Most did not. I wrote to them to see if I had done something wrong or if there was a bad batch. But never heard back from them. Does anyone have any other ways to fix rust besides POR-15 or a new fender? The rust is surface rust, the paint is slightly peeling (less than a dime sized spots). There are no holes through the metal (at least not that I can tell). I am having the fender flares painted to match my truck, so now is a good time to fix that rust. Any ideas? The paint shop suggested Rustmort. I have heard of Zerorust and Corroless? Either of these work??