Removing Mill Scale from Plate

[downsizingnow48]

Maybe I am the last person in the world to figure this out. The problem was, how to remove mill scale from an 18x48 piece of 3/16 plate. Yesterday I did an experiment. I laid out paper towels on a piece of plywood, then soaked them in vinegar. Put the plate on top. Laid more paper towels on the plate and soaked them. I started about noon yesterday, resoaked with more vinegar about 8pm, then started cleaning up at 6am this morning. First I used more vinegar with a scotch pad to loosen the crud, then Simple Green with paper towels to get most of it off, then spray glass cleaner and more paper towels to remove the last of the residue. This is much easier and cleaner than a stripping disc. Black glop on the paper towels vs fine black powder all over everything. Maybe there is an easier method, let me know, I have more plate to clean.

 

[GPintheMitten]

Nice job. I learned something from you. I don't know of anything better or easier.

 

[CNC Dan]

You might try a stronger acid. You can get hydrochloric acid used for cleaning concrete.

 

[rsallen]

The nice thing about vinegar is no hazardous waste cnc.
In fact none of the associated garbage that goes along with any of the stronger acids.

Thanks downsizing, I've got a half a dozen or so large pieces of plate out back I'll want to cleaned up before doing something with them. If I out figure out any modifications on your method that's any better I'll let you know.

 

[kennyd]

The secret is buying HRPO plate, only a little more $$ but well worth it.

 

[downsizingnow48]

KennyD is right on the HRPO, local supplier can get it special order with 2 day lead, costs close to 2x plain hot rolled. Of course by the time I do my own pickling (last night), and wipe it down with oil to prevent rust (this morning), that cost differential starts to look not too bad!

 

[roadhunter]

Interesting method that sure looks like it works.

 

[rsallen]

The secret is buying HRPO plate, only a little more $$ but well worth it.

The thing is ken, I got my plate for nothing but my time for loading and then unloading here.

 

[charlz]

Vinegar works good for rusty pieces as well, takes longer though, sometimes a couple of days. We have very base soil here that locks up the iron in the soil. When I dump out the used vinegar and rust it greens up that spot on the lawn

 

[Egon]

For real clean ?

Needle scaler, posphoric acid, sander, paint.

 

[skylarkguy]

That looks pretty good. Nice job!

 

[CNC Dan]

The nice thing about vinegar is no hazardous waste cnc.
In fact none of the associated garbage that goes along with any of the stronger acids.

Fair enough. You might try looking for stronger vinegar (200 grain vinegar) or the acid that is in vinegar.
Acetic acid, I think.

 

[Oliver1655]

Muratic acid is the dilute form of hydrochloric acid used to clean pool. While is is a great rust dissolver, you better rinse it well then oil or paint right away or it will rust right back up.

 

[downsizingnow48]

You might try looking for stronger vinegar (200 grain vinegar) or the acid that is in vinegar.

Didn't know about 20 percent vinegar (vs 5 percent grocery store vinegar). Will check around locally. Thanks!

 

[rsallen]

Could that be as simple as leaving an open pail out in the sun to evaporate off some water?

It's an honest question.

 

[downsizingnow48]

The stuff I am using is 5% acetic acid, 95% water. So evaporating the water would result in a stronger and more aggressive solution. The 20 percent (200 grain) vinegar is apparently sold as an organic weed killer in nurseries. On the other acid suggestions. I used to use muriatic (dilute hydrochloric) acid when we had a swimming pool in southern CA. It was pretty harsh stuff so don't want to use that. I have used phosphoric acid-based rust remover on old car suspension parts, it worked OK. I think I will get some as an experiment to see if it is better than vinegar on mill scale. The household vinegar is cheap though - $3 a gallon - and I don't mind waiting overnight for the relatively small amount of cleaning that I need to do.

 

[aczlan]

The 20% vinegar is usually listed as cleaning vinegar and is not much more expensive than regular vinegar.

Aaron Z

 

[Gary Fowler]

There is a produce called WEDAC which is specifically made for removal of rust and mill scale. It is a combination of phosphoric acid and a detergent. I have used it to remove iron contamination on stainless steel. Spray a diluted mixture, wait overnight and hose it off. Sometimes it takes a second treatment.
Best results is total immersion in a mixture of WEDAC and water and let it set till clean.
http://www.west-penetone.com/literature/1824.bul.pdf

 

[Egon]

The stuff Diary Farmers use to clean their milk lines and tanks usually contains phosphoric acid. Should be available at Farm Supply stores.

 

[weldermike]

Cool!