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Rust removal from tolerance critical parts ?

OK, I know allot about rust removal various ways. Normally for tolerance critical parts I would choose reverse electrolysis for anything that can be tanked. This simply dissolves the rust without harming good metals. Loosens frozen parts etc... and a great way to get rid of rust easy and cheap and safe.

So what about parts we can not tank, or things we don't want to dissemble much?

I have some thoughts and ideas but looking to see if anyone else has better ones.

I have not used my lathe/mill for a couple years, the oil coating dried up, it's very humid around here, all the bare steel not painted parts now have surface rust!

Of course I cannot just tank the entire machine! Far too much to remove and replace to totally disassemble to tank each part.
Do to critical tolerances I do not want to use any abrasives, no sanding etc.. and no grits in cracks crevises tight joints or bearings!

Even mild acids can get into the places I don't want grit above, as well as "soak" into porous metals. Once an acid, even mild ones, disolve rust they will often either eat into good metal or be the cause of much worse rusting later if not properly cleaned away.

So I have some parts to be making before to long and I find I have surface rust to some degree everywhere! Many parts I can easily remove and tank like the chucks, tool holder, compound slide etc.. if needed.
Getting stuff like the cross-feed bed off, lead screws, etc are a bit more difficult. Then of course there is the main bed.

I figure any way I clean my tools would in some ways perhaps be useful in cleaning up neglected wings also, or various ways of cleaning a neglected wing may be useful for the lathe too?

One thing I may try is a molasses concoction as it has a chemical effect to dissolve rust but is pretty safe, but then I'll probably have a big gooey mess and be covered with ants and bees for years to come LOL
 

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On some older (now restored) stuff around here I used a product called "Evapo-Rust" from the local Ace hardware store. The stuff that I couldn't soak i covered in those cheap-white (terrycloth?) shop towels soaked in the stuff then covered the wet towels with stretchy plactic wrap. That got the worst of everything off with 2 or 3 passes of that approach, then I went back with WD40 and the Scotch-Brite Ultra-Fine (Gray) or Light duty (Darker gray) pads.

This has worked for me on the deck of an old Bridgeport that had been stored dry, the ways of an old Chineese mini-lathe, and too many handguns to count.

A good de-greasing should be done first and immediatly beforehand (you'll create more flash-rust than you already have if you degrease then wait), For degreasing, I used that purple bio-degradeable stuff a little brush scrubbing and the light gray pads (with good gloves). Working one section/assembly at a time so that nothing waited too long before being covered.

The molassis trick (or coke, etc) is creating a weak acid with 'clinging' jelly-like properties. These are generally not much different than using a "Naval Jelly" type of product (weak phosphoric acid, IIRC), which does work quite well without leaving sticky water-attracting sugars and stuff behind afer treatments.

Don't put too much trust in electrolysis "not damaging" the underlying metals - electrolytic etching is a pretty common process for blasting off the surface of metals, which is what the rust removal process really is - The electrolysis processes we use to clean tanks is not just limited to the oxides, but the weaker bonds do usually break first (but not only).
 

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I recently used EvapoRust to remove the rust from the gas tank of my '78 GL1000. It worked great and is an environmentally friendly product.
 

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In my restoration buisness, I often have to polish rust and grime off of thinly plated tin. To avoid removing any plating, I use hot white vinegar. For the real bad stuff, I use ferric acid. I know your concerns for tolerances, but ferric acid will only remove oxidized iron. Never has been a problem for me, and some of this stuff is gold, silver, brass, etc. . To neutralize, I use sodium bicarb and hot water. Following that with a blow job,:ssshh: from the air compressor, and a bath of oil does the trick for slowing new surface rust development. I have even done this on fine firearms with no problems. Of course, ya don't want to leave stuff in there more than a few minutes. Just my experience. I restored 2 ShopSmith machines this way. One is a 1955 10R, and the other one I found on the side of the road, which was manufactured in 1998! Both were badly rusted. Now, they are used daily in the shop. Still dead on accurate. jimsjinx
 
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