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Three of the enemies in my shop are rust, zinc coating and black oxide.
1. Rust: No explanation needed. Rust is the enemy of steel, and steel is what allows us to tame wood.
2. Zinc coating: Many steel fasteners are coated with an ugly layer of zinc to protect them from rust in the outdoors. When I’m building stuff for inside, I’d rather not see the bright zinc.
3. Black oxide: Many pieces of reproduction hardware are coated with black oxide to protect them from rust during transport to market. This dull black oxide is difficult to strip off and looks wrong on reproduction pieces (in my opinion).
To tame these coatings, I usually use a citric acid solution or Evaporust to remove rust. Both are fairly safe chemicals that you can dump down the drain when they are spent. Citric acid also will remove zinc plating, though it struggles with thick coatings.
But neither of these chemicals can touch black oxide in my experience.
To remove black oxide, I usually use elbow grease – Simple Green and a woven gray pad. That’s a decent strategy for a big strap hinge, but it becomes ridiculous when you want to strip black oxide from 100 screws, such as those from Acorn Mfg.
(A personal plea to Acorn: I so wish you would sell your ferrous products without a black oxide coating. Many European hardware makers sell bare iron or steel hardware and do very well.)
So I have been looking for a way to remove black oxide that didn’t make me nuts.
Enter Charles Murray, an Ohio woodworker I’ve known for many years.
On Saturday, I ran into Charles while visiting the Woodworkers of Central Ohio. During our chat he mentioned he had been using “The Works” toilet bowl cleaner to strip rust from tools and hardware. And, he said, it’s about $1.50 for a 32 oz. bottle.
Intrigued, I picked some up at Home Depot and gave it a try today. I was shocked how quickly it removed some crusty rust from some T-hinges that have been sitting around the shop. Then I dunked some zinc-plated steel plates in the stuff. In 30 minutes it had stripped them bare – it took citric acid about six hours to do the same task.
Then I tried it on black oxide. I dumped some Acorn hinges into the solution and within 30 minutes I could wipe away the oxide and see bare metal.
What’s the catch? The Works is 20 percent hydrogen chloride. It is nasty stuff. You don’t want to touch it, breathe its fumes or get it inside you in any way. But when you are done with it you can put it in your toilet and it cleans it of lime scale, rust and hard water stains.
I do not like nasty chemicals. When I use them, I use them in small amounts, with great care and only when I think it is the best solution.
If you decide you want to use “The Works,” download its MSDS here. Read up on hydrogen chloride here. And check up on the product at its web site here. Use it with great care and adequate protection (chemical-resistant gloves etc.).
And ask Acorn and other hardware makers to stop using the ugly black oxide in the first place.
— Christopher Schwarz
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