De-rusting with vinegar
When I venture into garage sales and antique shops, I often end up buying a few rusty tools.
My technique for cleaning them up is to soak them in cheap vinegar for a week -- then rinse them off with water, while scrubbing them with a handheld wire brush -- and then drying them with a rag, and spraying them with WD-40 (and also spraying the bristles of the wire brush, so that it doesn't rust!).
Some people use something alkaline to "stop" the acid. I used to make a solution of water and baking soda and dunk the tools after the initial water-rinse -- but I stopped doing that long ago, with no apparent(!!!) ill effects.
Also: if you're as cheap as I am -- pretty much anything acidic seems to work. I've used my wife's expired Diet Coke (the artificial sweeteners turn sour after a year or so), and also the squeezings of lemons that have started to go bad. They all seem to work -- although I hedge my bets my mixing them in with the vinegar.
Here's a recent example. I'd picked up the tools at a garage sale a few months ago.
I have a few different plastic tubs to choose from. I try to get one that best fits the size of what I'm soaking, just to make the most efficient use of vinegar.
Here's the tools submerged in vinegar. I also have a few rocks that I put in, to fill in the empty spaces. Note that the metal pieces are touching each other: this doesn't seem to be a problem; the "touching" areas also end up de-rusted.
Then I just put it off to the side, and wait a week. Occasionally I'll jiggle the tub a bit, so that the vinegar slooshes around. It could be that my agitating the tub occasionally permits the rust removal at the points where the metal bits are touching.
By the end of the week, there's a weird layer of orange foamy scuzz floating on the top of the vinegar. But it's harmless. I just dump it out on the lawn.
One of the people on the woodworking handtools e-mail list that I belong to says that two days is better, because longer than that and the vinegar actually eats into the metal itself. But I haven't found that.
Plus, for me, "from weekend to weekend" suits my available worktimes.
And, here's the finished results. I've used this de-rusting approach a lot over the years -- but never with items with moving parts. So I was pleased that even through the wrench and the callipers were "stuck" when I put them into the vinegar, they actually moved freely once I took them out.
I actually took the wrench completely apart to scrub it with the wire brush, and I dried it and WD-40'd it inside and out.
Some people don't like the resulting grey color. But I think it's pretty cool.
Note that when you rinse and scrub the items under water, it tends to stain your hands.
Also, I end up having to use soap and water to clean the residual WD-40 off of my skin. I should probably wear protective gloves.