Arc Euro Trade used to do a rust remover that worked really well. They may still sell it. It removes rust without discolouring the metal.

As it is a flat bed you can use a brand new Stanley knife blade to scrape across the surface, at a fine angle not like a scraper, and lift off the tiny rust nodules, after oiling. Bit like shaving. It might be a little hazardous if you are not steady handed.

Then perhaps a small brass wire brush, making sure it is brass not plated steel. Then the scourer, by hand. You would have to thoroughly de-oil to use a liquid (phosphoric acid) anti rust. Also avoid wirewool unless the ultra fine variety but that is still a scratch risk probably more cosmetic than damaging.

As you have probably run the saddle up and down to 'test it' you should remove same and clean the bearing faces underneath as they will have picked up some rust aka grinding paste.

I would never waste effort on a mechanical method of removal – why lose any good metal when there are so many chemical approaches that won't affect sound steel/iron? bear in mind rust contains a huge amount of water that 'puffs it up' so it can look far worse than it really is.

If you can find Evapo Rust at fair price, try it. Someone recommended it on here so I arranged a review.

I was knocked out by how well it worked and it's non-toxic. See MEW 233.

the two pics below are a day apart, but to be honest the stuff works in 30 minutes to an hour. It uses chelation rather than acidity.

Neil

Edited By Neil Wyatt on 24/09/2015 19:53:02

The colour is because on carbon steel the carbon in the rust gets left behind as a loose coating

It's not too bad, its different from the iron phosphate coating that becomes part of the surface that some rust removers leave, and different from the effect of electrolysis that creates patches of magnetite. On some stuff (chrome-vanadium sockets for example) it rubs off with your thumb. If you leave the ER on it acts as a rust preventative but it has a slight stick feel so I washed it off and oil the items.