[ekbmuts]

Anyone know of a chemical way to get rid of mill scale? Meaning, other than using a flap disc or wire wheel?

[Arno]

Commonly a bath in hydrochloric/muriatic or sulfuric acid will take it off.

Take the proper precautions though. Gloves, glasses , covers, etc. as you don't want to get that on you.

Also the acid fumes will attack lots of other parts in your workshop too so good ventlation or working outside and washing off the parts and oiling them before bringing them in is preferred. Acid-stripped steel parts will (flash-)rust in no-time flat.

Bye, Arno.

[ekbmuts]

Arno, Thanks. Ever tried plain old white vinegar? Fumes and all that from acid will probably freak my co-workers out so looking for something a little less potent.

[ekbmuts]

So I did a little test with plain old white vinegar. It takes a little time but it eats the mill scale right off. Funny, when I MIG (or flux-core) weld, I can just ignore it. TIG welding is another story. Every time I miss some or forget to get rid of it, my weld flares up green, ruins my tungsten, dirties up my glass cup and generally ruins my day. So, white vinegar.

[cj737]

Distilled White Vinegar will work on thin mill scale pretty well. It’s a mild acid, not too destructive to the base material, and certainly less odorous than aggressive acids. Once the vinegar stops bubbling, it’s done its best work, so prolonged soaking does not do a whole lot more.

[ekbmuts]

Great. Do I need to neutralize the metal prior to welding with baking soda or some such?

[cj737]

Just a good clean per proper habit. It’s mild enough neutralizing is not required.

[907jeff]

I've had great results with 30% cleaning vinegar. You can find it at Lowes, Home Depot, etc. An overnight soak at the longest, and the scale just rinses right off. Then I give it a dunk in a solution of 1 cup baking soda/gallon water to both neutralize the acid, and prevent flash rusting. And it will rust pretty quickly if you don't do something to stop it.