Remove rust from machined metal

So I'm replacing my pinion seal and there is rust on the inner surface off the diff that I need to remove so that the seal sits perfectly. I recently replaced the seal, but it got scraped up and ruined by the rust. What type of abrasive should I use to remove the rust without scuffing and putting the metal surface? Thanks

 

This is the new seal that got trashed.

 

Honestly, what I would probably do is clean that whole thing with alcohol (it evaporates super fast so it it doesn't stay on the metal and rust) then I would use duck tape and "mask" the splines/threads so they don't get chewed up and I would wire brush it, sand it, wire brush, dremel wire brush, sand, and do everything I could do that off of there.

After that I'd probably go with Rustolem Rust Reversal bath and see what that did if I wasn't happy with it. 15 minute bath, wire brush, sand, repeat until I was satisfied with it. I would just make sure you REALLY duck take the splines and threads so the brush doesn't hit it.

 

Thanks for the advice. I have all said materials except for sand paper. What kind should I look for, fine or ultrafine or emerycloth paper, or something like 0000 steel wool?

 

To be totally honest with you, I would go in stages... It can take a while, but you'll get it right. If it were me, I start out with something super coarse, just to get the rust off. Then when that did some good damage and I started to see metal again, I'd probably move to something less course (more fine) and then go another step. Final step would be to go around it or over it to polish it with some steel wool if you REALLY wanted to get it shiny and new.

Once you get the seal in and everything looks good you might want to look at Mavcoat (Wheeler's sells it) or some WD40 White Lithium spray grease just to coat the metal as a preventive and just re-apply after you wash it, a hard rain, or when you feel like doing some maintenance on the truck. Trust me- this will take a good couple of hours to get right and you won't be forgetting about it anytime soon.

You might even have to do in 4 stages with the sand paper on an axle seal, but that's what I would do.

This isn't something you can really screw up, it just takes a TON of time. I almost exclusively use alcohol (the cheapest stuff Wal-Mart sells and a $1.00 spray bottle- which is also at Wal-Mart) for stuff like that to clean it up. It evaporates quick, doesn't leave residue, and still cleans.

 

To get an idea of how much work you are going to have to do- start on the outside of the housing (after masking the splines and threads) and hit it with a wire brush in your vice so you can really get good pressure on it, and then you'll have a good idea of how it's going to be.