I've enjoyed reading all over these forums about finish options, the different techniques people use, and I've been experimenting with various wax options, spray on lacquers, etc.  One of my instructors produces some really gorgeous candle holders and he was telling me about his process, which includes a muriatic acid wash step.   Being totally new to this, I basically produce pieces, clean 'em up, polish a few, wax 'em and smile.   So this weekend, not wanting to mess with muriatic, I experimented with soaking a few pieces in vinegar.  Was very pleased with the look on some butter spreaders, but didn't like the look on some other, smaller pieces.   

 

So I'm just curious about what you guys do.  Do you ALWAYS acid wash... only on particular types of products (and if so, on what, and what is your deciding factor), or do you never do it.   

Depends; cleaning the scale off sure extends the life of good (expensive) files in knifemaking, (also grinding belts for that matter) so cleaning off a forged blade is generally done in some way---knew a maker that sandblasted his.

 

The dark scale finish is just right for a lot of things---like a cooking tripod made from 1/2" sq stock.

 

OTOH I just made a half dozen cubical hooks that get painted and after wire brushing the first one, the rest got dumped in the vinegar bucket...

I don't use acid as much as I should.

 

I do like to use acid with a penny stuck in it.  The way the copper coats the steel is neat, especially if you use a funky wrought iron.

Hmmm, haven't seen mention of that trick, I'll have to try it.

The only trouble with acid, IMO, is that you have to get a good "kill" on the reaction or the parts will rust. I used to produce a lot of wholesale items for the craft trade and always tumbled those in a large drum with a little blasting sand added to help with scrubbing action. BTW, you can get a pretty decent kill with a mix of ammonia and baking soda dissolved in tap water - but the metal needs to be protected quickly or it will flash rust from exposure.

Trisodium Phosphate (TSP) disolved in water works well to neutralize acid.

Just as an aside:  I'd read on some thread here where someone said "anything muriatic acid can do vinegar will do, just more slowly."   I had a couple of open end wrenches I'd picked up for a nickel a piece, unknown coating on them so I stuck them in a vinegar bucket to see what it would do, along with some other pieces I'd forged last weekend.  The other pieces did as expected, ate up the scale nicely overnight, cleaned up nicely.  The wrenches have now been sitting in vinegar for 4 days straight... .nothing.  Nothing at all, the coating hasn't got even so much as a pock mark.  WT?   All I know about the wrenches, other than the exorbitant 5 cent price tag, is they say "drop forged" and "made in china."  Anyone have any idea what the coating can be that is utterly unimpacted by soaking in vinegar for 4 days?

It could be plutonium 235.   Whatever they have on hand that day will do.  If a few workers die, they have 80,000 waiting outside to be hired. If the vinegar hasn't worked it's magic in a day, I would assume 4 days won't help.  I think you got off cheap.   

Maybe they are chrome plated? Greasy? Made in China ;)

painted?

Dunno, all I know is I ended up leaving them in the vinegar a week, they emerged pristine as the day I put them in, utterly unfazed. I'm going to find another use for them that doesn't involve melting plutonium or who knows what in the forge! Better safe than dead.

There is a black phosphate coating (Parkerising) used on, among other things, firearms and tools. Utterly impossible to get off to refinish without becoming a major PITA. I am not even sure you could burn it off in the forge. I suggest the abrasive tumbler or wire wheel on a grinder. 

Possibly painted, but it's a bright silver finish like I'm accustomed to seeing on pretty much all wrenches.  

Shiny silver usually means hard chrome over copper primer. It will burn off in the forge, but the fumes are to be avoided.

Generally I avoid putting plated metal in the forge:  Chrome, Cadmium, Nickel, Copper, Zinc, etc all double plus ungood to breath in.

My shop is outdoors with plenty of cross-ventilation, but still gives me pause on burning that off, more worried about what it'd do to my gas forge!

If one has no other method of removing metal coatings (such as chrome, zinc, etc.) on steel items except burning them off in a forge, you can set up a box fan blowing across your forge and away from the area in which you are working.  The concern there is, of course, air pollution with heavy metals :(. Since working with strong acids is problematic, I have removed the coating on chrome plated wrenches with success in my outside forge with the fan blowing over it.  Also, I don't linger around the forge except to do a quick check on the heating process.