Cleaning up Corrosion on the Front Spar

Now that all the rivets and fittings are off cleaning the light corrion and remainging crud on the spar is easy. First I washed off any remaining paint residue with MEK. To clean the corrosion I glass bead blasted with AC beads at 20 psi. Glass beeds can be sieved and re-used up to 30 times if you keep the pressure low enough not to smash the beads, and blast at a 45 - 60 degree angle so you're scrubbing the surface not just peening it. When I first bought glass beeds the young lady selling them explanied that the pressure should be very low, if you can see something happening it's probably to high. This was slow work but well worth it to make sure there is no corrosion trapped and growing under the expoxy primer when we're done. Also, you're only blasting any spots of surface corrosion. This is a 53 year old spar so there was a fair amount even if nothing serious. The biggest problem was how to get a wing spar in my blasting cabinet. There is a door on one side so I put a metal cutting blade in my circular saw and cut a hole in the other end of the cabinet so the spar could pass through (this will also work for grit blasting the wing struts). I then took some scraps of a stiff foam rubber and made plugs for the holes. I cut the plugs about 3/4" large than the holes and split the edge of the foam so it fit over the edge of the metal making a nice seal. I adjusted my roller stands for my table saw and placed one on each side of the cabinet for the spar to roll on. Next I cut "I" shaped slits in the foam for the spar to pass through laying on it's side. Problem solved, no mess in the shop, put on a head set with something to relieve the boredum and blast away. The spar really cleaned up nice. With the cleaning done the spar was treated with a Phosphoric Acid Etch & Brightener, and then a Conversion Coating to assure no corrosion is left and the primer bonds well.