With the frame modified and refitted, the next step was sandblasting the rest of the rust and paint so it could get a fresh layer of primer and frame paint. I had bought a used 40-pound pot blaster from Craigslist and had to make some minor repairs to it to get it working right. On Saturday I picked up a line dryer, pressure regulator and coal slag and went to work. I set the frame on sawhorses in the backyard, put on a respirator, goggles, ear plugs and welding gloves and got started.
I quickly discovered two problems. First, the previous owner had apparently not used a line dryer and there was too much moisture in the pot blaster. The coal slag kept clumping and fouling the lines and nozzle. I wasted probably half a 50-pound bag of slag just trying to future out what was wrong, and when I did get things somewhat working, I realized the coal slag was no match for the remaining paint in the frame. I had bought the coal slag because it was $9 for the 50-pound bag. It was not worth it.
I did some more research on how or tune the pot blaster for better results and on Sunday bought 50 pounds of 80-grit garnet media. It cost $25, but man did it work better. I think part of the problem was residual moisture in the blaster pot, which the coal slag helped drive out. With a dry blaster and good media, I went to town on the frame, but even the garnet was not strong enough for some of the remaining frame paint. I decided that if a sandblasted couldn’t get rid of it, then I could probably leave it without much worry.
Once I got the frame to a point that looked acceptable, I cleaned the remaining media off the frame with compressed air and prepared a phosphoric acid solution to treat the metal and any remaining rust. There are several companies that make such a product, which you spray or brush onto the metal and let it sit for 30 minutes, then rinse with fresh water. I worked quickly to get a first coat on with a brush, and realized that was not going to get into all the nooks and crannies, so I loaded up a pump sprayer and finished the job. I flipped the frame to get all surfaces and let it sit, and then rinsed and dried the frame as much as I could. I had to flip the frame a couple more times to get all the drain water out of the frame boxes.
It seems like a lot of work so far, but the frame is now ready for primer and paint. The phosphoric acid created a protective layer on the steel so it won’t rust again before I can hit it with primer next weekend. Here are some pictures of the frame:
Next week will be primer time. Can’t wait.