I’ve seen a bunch of videos of people demonstrating things like muriatic acid and household vinegar and phosphoric acid and I’ve left metal in buckets with the above and even evapo-rust for up to a week and the mill scale never seems to come off the way I see in videos. What am I doing wrong? I don’t mind getting rid of mill scale on the outside of angle iron with a grinder but getting into the inside is just kind of a pain and I’d like to find a better way.
I’ve recently tried “cleaning vinegar” and it did a little something to the mill scale after a few days but it would still require manual scrubbing. What can I use that will take off the mill scale and rust and just leave bare steel in like 24 hours or less reliably?
Happy day to you. I have worked with all the above stated methods minus the evaporust. My experience unless you sand blast which can cause distortion the white canning vinegar is the best option its cheap! If money isnt a issue then i would get the more expensive 30% concentrated or even something stronger. Make sure you cover it so doesnt gas you out. and evaporate to quickly. Temperature makes a difference but still takes time. Having a pressure washer before, between and after thats whatever surface residue off and allows the acid to react. Now that said this is esentially a pickling process and if speed is the essence the a stronger acid such as muriatic or sulfieric works quicker. I have had success spraying muriatic with a spray bottle and wire brushing/sanding between coats and removing heavy scale in very short periods of time on say 15 square feet of 1/2" plate. My experience the thicker the plate the heavier the mill scale.
Hope this helps there are many more experiential tricks but some are shared and some are learn
I use 45% vinegar but I dilute it with about 8 gals of water which makes it slightly stronger than normal household vinegar (5%)
24 hours may be ok for fresh vinegar but not if your using it over and over.
I normally do tube which has a oily film on it. it pays to wash that off first as it makes the vinegar nasty.
So I will soak parts for at least 24 hours, rinse with water then 15 min soak in water baking soda mix (1 normal size box to 5 gals of water) I have parts that have set for months with no surface protection and no to very little rust after doing this. It is in a conditioned space though.
Remember, this stuff over time will get on stuff in the sounding area and cause it to rust if it can.
PS there are times where I will have to take scotch brite and run over the stuff to get it down nice and clean.
I’ve tried the vinegar and it works, but it’s too slow for me. I use muriatic acid just a few minutes and it will come off with a scrub brush under running water.
Last time I tried muriatic acid I was really unimpressed with it. I got some from the hardware store in the paint and concrete finish aisle so maybe it was low concentration or something (sure didn’t seem like it) but I stuck some angle iron in a bath of it as it came out of the jug and after an hour it seemed to have made no difference. It was about 25°F outside where I put it at the time and that may have had something to do with it but my results just seemed really bad compared to what I’d seen other people get. After about the 4 hour mark it needed intense scrubbing and the mill scale didn’t even seem to have loosened compared to doing nothing.
I’ve found oil on the mill scale really inhibits any of the acid bath solutions for removing mill scale. Anything from making it really slow, to ineffective. Same goes for anywhere two parts touch.
Also, your suspicion about low temps effecting the process are correct. The higher the temp, the faster the acid eats the mill scale. Agitation helps as well. Maybe a cheap aquarium aerator would be worth a try.
Vinegar is somewhat slow but I normally cut all my steel to size late in the day and soak overnight. I wont use Muriatic acid due to all the issues with things in the area of where its being used rusting. And I don’t like the idea of pouring it down the drain
not sure how it compares pricewise to the acid, but have you tried the 45% vinegar?
My latest attempt was with 30% vinegar in a semi-sealed tub outside and after a week or so, maybe 80% of the mill scale rubbed off without too much effort. It’s definitely the best so far. I hadn’t degreased any of the parts before I tried this so I’m thinking that must be the remaining issue. I like the idea of the aquarium agitator.
The end state I’m leaning towards now is a very long wooden box with a lid I can put the semi-sealed plastic tubs in to keep the sun off them. Then, one tub is a vinegar bath and the other would be baking soda. Maybe aquarium agitators on both?
A lot depends on the type of steel. Things like channel and angle can have crazy thick and tough mill scale, that will always be hard to remove. But the best way to deal with it on things like plate products is to not have to deal with it at all. You can buy scale free steel and depending on how you value your time, that may be your best option. Pickled and oiled plate is often not much more than your typical hot rolled and once you try it, you won’t go back. Cold rolled is also an option for some shapes.
Boy your advice is good. Unfortunately, the only steel supplier within a couple hundred miles of me doesn’t have any options like that. I’m lucky they carry multiple thicknesses of similar materials, let alone more options in 1018 vs A36
This doesn’t answer your original question, but.
There’s a somewhat recent development in the de-rusting world. Beyond Ballistics has presented an easily made alternate to Evaporust. And it’s good. So naturally i’m wondering how well it does on mill scale in cases where anything else would also work.
Here’s the vijeo with recipe etc.
Did you cut it with water or just use it full strength?
I would think you would have seen good results if it was straight.
I did read through this thread and forgot to mention that I am doing 90% tube, and I think this cleans up much easier than angle and maybe some others.
I just did some Friday with around a 6% solution of Vinegar and let it set for about 13hrs. I washed it first with wash thinner to remove the oil, then vinegar. I did take some scotch brite and go over then into a baking soda mix for about 10 mins and it came out pretty good.
Has anyone tried the Montipower bristle blaster?
Seems expensive for what it is and hard to tell how fast it is, and I would think the belts don’t last too long!?
not a chemical process but has anyone rigged up one of these cement mixer parts tumbler jobs I’m seeing on the TUBE? I re use a lot of junk iron and thought for smaller parts I could do like Knick cut my parts the day before and put them tumbling for the Night? My shop is a long way from the house, sound shouldn’t be a problem. you can find those electric cement mixers on the old market place all day long for like 150$. one guy I saw put a pile of old screws in there for media. looked like it worked pretty good, but could have been the magic of the internet?
I did research this a little awhile back and just never followed through.
I make a small hook assy that has some welding done on it. I was thinking this would be a good way for cleaning them up before powder coating.
It never went any further, I was not sure I would get enough use out of it.
But I definitely think they work well for small sized parts.
I like you, like the idea of letting it run while not there.
I haven’t done the cement mixer version, but I bought an extra barrel for my brass tumbler and use that with polishing stones for small parts. If I had to do a lot of larger parts I could see the cement mixer saving a person a lot of time.
