What are you folks using to deal with millscale? I see they make those auto sanders but really costly. Is anybody leaving the millscale on say signs and painting? Does the millscale REALLY need to come off?
I searched the forum and saw some say drum sander and a few use concrete mixers- but the mixers are probably stupid loud and I really wouldn’t put a sign or thin gauge metal in there. The drum sanders would be good for cleaning up outside edges. I was thinking like a belt sander maybe like you would use to refinish a hardwood floor? Millscale gums up grinding wheels not only that grinding wheels mark it up tooo quickly. Then I read about a guy soaking in vinegar but I couldn’t see that removing millscale just mayb cleaning the surface of some light impurities. About as effective as salt and lemon juice really. If you can get your hand on real pickling solution the used solution is technically hazmat. I hate millscale.
I can tell you from experience that vinegar definitely removes mill scale. The 5% stuff from the grocery store will work overnight or maybe longer. You can get 30% cleaning vinegar from Home Depot that works faster.
I cut things and toss them in a tub of vinegar and leave them for a day or two. Then I rinse them off with a hose and let them dry. The vinegar also removes the majority of the dross.
The vinegar eventually loses it’s acidity and needs to be replaced.
By far the best solution. I have I few different size plastic tubs and the large plastic lined tray (7’8" x 3’8") for when i need to do very large things. I normally buy the 10% cleaning vinegar from ours hardware store and leave it in overnight.
Vinegar works, no question about it. I usually use 2 gallons of 30% and 3 of 5%. The longer the soak the easier to get it off.
I take them out and soak them water mixed with baking soda per @Knick recommendations(1 cup per gallon) to mitigate the flash rust. It totally works. I have left the parts uncoated for months with no rust!
I have a clear plastic storage tote. I think it’s 30x18x6” or something like that. Then I have a plastic lined one I made out of scrap lumber that sits on saw horses when in use. I used the original drain for my crossfire pro on the plastic sheet to drain the vinegar. First used a kennel crate liner with the pro drain but it didn’t last very long.
I have muriatic acid I use to clean concrete anyone use that on millscale? It’s significantly stronger than vinegar I’d think it could cut the soak time in 1/2 ?
Citric acid. It comes in granular form in a bag from that evil website so you can mix to your desired concentration and works just as well as vinegar without the smell. A couple hour dunk (ensuring all surfaces are exposed), and the scale wipes off.
Always wash your parts in an alkaline solution after wiping the mill scale off to stop the flash oxidation.
10lb bag for $40. I use a cup or two per soaking solution (5 gals normally). No idea on timeline of effectiveness, as I often need the room before I deplete the efficacy.
For the storage alone vs dealing with liquids, worth it.
Oh yea. Minimal stirring required unless you saturate the mixture. Get some pH strips (or a roll of it from said evil site), and mix until 0-1 pH. I usually stir in a homer bucket with a spare metal rod.
