I have an '04 Tacoma and live in an area where salt is used on the roads during winter. There is visible rust on my frame, so far it appears to be surface rust. I purchased the truck new in 2004 and currently have 75,000 miles on it. I removed the skid plates to clean off some spilled engine oil. After removing the skid plates and using a degreaser with a pressure washer I noticed a considerable amount of surface rust. The plates are still sound so I cleaned them up a little more, primed and then painted them with a rust blocking spray paint. I was satisfied with the results. I was contacted by Toyota back in about 2008 and told that the corrosion warranty for my frame was extended. Now that my truck is 12 years old and past it's warranties I'm thinking about painting my frame. A guy I know restored an old Chevy truck and while he had the frame stripped down to the bare metal he had it powder coated. That's a great solution, but probably very expensive and not very practical in my case. I've considered painting the frame with the body left on the frame, but I don't think I could reach everywhere I need to get to. I don't think taking the bed off would be too difficult, but that would only take care of half the problem. I don't think frame corrosion is as much of an issue if the vehicle is being used in warmer climates. The dealership inspected my frame some years back with a small hammer and told me it was sound. If anybody out there has had experience with rust proofing their frame, I'd love to hear about it. Unless you live in an area like mine where salt is used on the roads, I don't think you have much to worry about.