Chromed key stock?

[bgf]

I can't find simple hot-/cold- rolled mild steel in small solid square section locally, but I have some 1/2" key stock.  It appears to be chromed (zinc chromate?).  Commonly this appears to be 1045 or similar steel, which should be fine for what I want to do with it, and I only need a couple of small pieces.  What is the best way to remove the coating?  Before I start trying toilet bowl cleaner and other stuff, maybe someone knows exactly what to do -- worst case, I'll just file it off !

[Acer Saccharum]

Zinc fumes are TOXIC. Don't burn it off.

Only Slightly Related Dept: I found that I can get square 1095 keystock thru McMaster-Carr. Comes in 1' sections, in many sizes. Handy for woodworking tools, springs, etc.

[mark esterly]

we strip zinc off steel tubing at work with hydrochloric acid. fumes from this are also toxic. 

[Elnathan]

I have used muriatic acid to strip zinc off a bunch of pipes for a forge. It it worked quite well and fast - less than an hour, I believe - and was readily available from the hardware store since it is used to clean pools and concrete (IIRC), but is fairly nasty stuff and has to be neutralized with baking soda before dumping.

I haven't tried it, but I believe that vinegar/ascetic acid will also remove zinc, but works a bit slower - overnight or 24 hours or something. Just don't drink the vinegar afterwards...

I admit that I have burned zinc off masonry nails while annealing them with a propane torch, just being very careful not to breath the fumes, but that was probably not a very wise practice. If the key stock isn't hardened, I would probably just go ahead and file it off. I used to have a 5/16-3/8" galvanized steel rod until I turned it all into various tools - worm, ball puller, a punch to remove tumblers from cocks - and I just filed to the shape I wanted and if there was any zinc left on it at the end I filed it lightly until it was all gone. What you are dealing with may be a bit more difficult to get off than simple galvanizing, but I'd try filing before breaking out a lot of nasty chemicals.

[snowdragon]

Just sand if off. You'll probably need to start with some rough grit to get it started, then go finer.

Oh, just had another idea. If you have a torch, and you're sure it's steel underneath, you can heat it red and it will probably turn black and sluff off.  Bill

[kutter]

A small piece of stock or some screws,,,,Burn it off. Takes a few seconds.
Yes the fumes are toxic & nasty smelling,,that why they're called fumes.

Don't do the burn off in the kitchen, don't stand in the smoke,,,all the normal common sense stuff.

When it cools off,,wire wheel/brush it and you're ready to go.


No worse than mixing nitric and old nails to make your own AF..

[4ster]

I haven't tried it, but I believe that vinegar/ascetic acid will also remove zinc, but works a bit slower - overnight or 24 hours or something. Just don't drink the vinegar afterwards...

My other hobby is scuba diving.  A lot of the critical metal gear (like regulators) is chrome plated brass. When these  get gunked up with salt and crusty stuff it is a common practice to do a quick soak in white vinegar.  It works great for getting the fitting clean. 

If you leave it overnight in vinegar it removes all the chrome too!  (Don't ask me how I know this.)

I would try soaking a bit of your key stock in vinegar to see if it pulls the chrome off.  It seems to me that it may discolor the steel though.

[bgf]

Thanks, everybody.  I did strip the smaller piece I needed with a file last night, and it wasn't too bad as that piece needed shaping almost all over anyway.  On the larger piece which will/should remain square for the most part (base for rear sight and shader hood), I'll start with vinegar and try chemicals in progressively harsher form until I find something that works; burning it off is also a possibility, but I'll save it for last.  I'm pretty sure that 1045 is a reasonable guess for the steel underneath, as it works pretty easily but a little harder than mild steel.

[ironwolf]

 Set up a fan, stand upwind, burn it off with a torch.
 
    KW

[Habu]

Only Slightly Related Dept: I found that I can get square 1095 keystock thru McMaster-Carr. Comes in 1' sections, in many sizes. Handy for woodworking tools, springs, etc.

Thanks for that--I've got a couple tools I need to replace and was beginning to look for a source for stock. 

[Pete G.]

FWIW: Welders in the shipyard used to hate having to weld galvanized pipe. When the fumes made them sick they drank milk as a remedy.

[Hungry Horse]

The old saying metal workers repeat when asked about burning off zinc plating, or galvanizing, is "first you get a sweet taste in your mouth, then you get high, then you die" don't burn off plating, the material that vaporizes into the air eventually settle on everything near by. Over time this toxic material reaches levels, that when stirred up, and breathed in, will do you harm.


                       Hungry Horse

[JCKelly]

Good old fashioned lye (sodium hydroxide) dissolves zinc very nicely.
No fumes, no problems - just don't get the lye in an eye.

I really do not know if this is cold drawn metal but I suspect the mill cold drew it to get that nice square shape.

Which means it has high residual stresses in it.

Which means if you machine something from one side it will curl or kink.
Surprize!

Ask me how I know.
I'm a metallurgist, but . . . didja ever hear of the Shoemakers children . . .?

So, after you dissolve off the zinc, heat the steel with your torch until it just begins to glow in poor basement lighting.
No need, or good, in heating it cherry red.
Just hot enough to start to glow a little. That will get rid of the stesses and you can file or machine stuff that will stay put.

[bgf]

JCK,
I'll try sodium hydroxide next; the results with vinegar aren't promising, so far, but I wasn't very patient.  I think you are likely right about it being cold drawn -- very sharp corners.  I didn't notice any warping problems with the piece I started on already (maybe b/c it is symmetrical), but it won't take any time to heat it up and relieve any stresses just to be safe, it could save me a lot of grief later, thanks.