Mark, In the marine business in southWET Florida I've learned to use a product called OSPHO, and it's a rust converter. Recently, I needed some here in Indiana and couldn't find any, so I bought a product at Menards (kinda like Lowes and Home Depot). It's by KleenStrip, which is a recognizable brand and available brand.
There are two kinds of Rust, FE2O3 and FE3O2, and I can never recall which is which. BUT, if you pick up some 4130 tubing or plate you'll see that it is very dark in color. That's the good rust, and if you'll take some sandpaper and clean some of it off, you'll get the Orange stuff we commonly call rust (usually overnight). That black coating normally forms at a higher temperature, which is why your welded parts have dark joints, and hold up pretty well with no support on your part. The OSPHO or RustConverter turns red rust into the black kind, and it's quite hard, and you should paint right over it. In my usages, it seems to do somewhat the same thing on bare steel too. It's complicated chemically, but easy to do. It's why we also just wire brush a welded airframe and NEVER clean it "bright" before chromating (ancient technology) or epoxy painting You must first clean off scale and oil. After treating the holes and your scraped up bolts, I would then put some epoxy on them and push them into place. Another thought; you can get an adjustable reamer at a machine shop. Those have a small screw protruding from the "business" end, and you can adjust them up to maybe .005 over nominal size. Bring those holes out to a reasonable fit, and use new bolts while you're at it. There's many an aircraft bolt that's been scraped a bit at assembly, and we never hear much about it if they're in a dry location. Keep on keepin' on..... Ron Freiberger mailto: rfreiber...@swfla.rr.com
