Henry, clean your steel way more than you think before using any type of acid for rust removal. Muriatic is the most effective I found. If when you are done and some areas of the steel profile still have thick scale, try using your oxyacetylene torch with your cutting head. Applying short bursts of heat will help pop thick scale. I like this heating method, especially if you are using wax or oil-based finishes, because the heat helps dry out your parts faster.
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I don’t have an oxy setup yet, but I definitely like the idea of something kinda quick to run through like that. It’s not like removing mill scale with a grinder is the worst thing I’ve ever done, but it can definitely get old after awhile.
It rates in the top 5 for me 
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It’s not so bad on the outside, but getting it off the inside of a piece of angle iron is really annoying. I don’t even have a good disc for it. I tried the Walter Flex Cut Mill Scale discs and they work great, but they all seem to be so out of balance they killed the bearings in one of my grinders.
I don’t mind removing from big, flat pieces, but I almost never use those anyway.
This is after degreasing, 24 hours in a 30% concentration vinegar solution and some scrubbing before putting the piece in a neutralizing tub filled with baking soda and water.
Have y’all gotten better results? I’m thinking about the tumbler, just not sure I want to invest in building and running one yet.
To add to this, another piece went for a similar treatment and was in the vinegar about a week at this point and ended up looking exactly the same. I’ve seen guys on YouTube showing the metal shiny after and it’s just confusing me.
Those results look the same as what I get on HR steel sheets from 5% acidity vinegar with the same cleaning step and soak time. (although I clean in soapy water, not degreaser)
The scale on angle is a lot tougher stuff. Usually I’ll hit it with a cupped wire wheel about halfway through and it’ll come out pretty scale free by the 24hr mark.
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Same as what I get on tube.
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I’ll try adding the wire wheel step. I like using angle for a lot of things, I just wish it didn’t have the scale like that.
Well I got the market place shuffle pull on me! It was sold when I got home! Now just gotta wait till goes on sale again at harbor freight, much as i’ld like to build one, I got to many other projects at front of the line
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If you plan ahead you can often order what you want from your steel supplier and get it with their next steel order. Might be a few weeks if you are out in the stix. Hot rolled angle and other structural shapes are not really made with the idea of clean bright metal. The mill scale actually adds some protection. Typically, only the weld areas are prepped clean and often not even that for a rod like 6010. You can order cold rolled angle if you want something smooth and clean for TIG welding. Your projects will dictate what would be the best material to use.
But when push comes to shove it’s hard to beat pure muriatic to get that stuff off, as long as you have a place to deal with it and all the right PPE.
It’s much like taking off rust. Many ways to deal with that, too.
Yeah, there’s only one supplier within roughly 120 miles and their selection of cold rolled is extremely limited. It’s otherwise a great suggestion, it’s just not an option (I’ve asked). Even getting stainless or aluminum is either a matter of paying roughly 6x the usual price or driving to the nearest metro for it.
What about HRPO (hot rolled, picked and oiled)? Sometimes that’s available when CR isn’t.
Unfortunately they only offer hot rolled just as it comes out of the mill. I think the only thing they even offer in cold rolled is tubing and they’re missing a ton of common sizes and thicknesses of that.
If you don’t mind me asking, roughly where do you live? You might be surprised what’s out there sometimes (but not always). I found a guy making titanium parts a material supplier by finding a company who had large enough scrap to be used for his product. That wasn’t as hard as it sounds because he lived in central California and just hadn’t done the legwork to go find someone besides the first company that he started to buy from.
Maybe someone here on the forum has a lead on a company you could reach out to that’s closer than 120 miles that buys a decent qty of material and is willing to be a middleman for a 5-10% markup?
Arizona, about 80 miles south of highway 40 near New Mexico border
Is it safe to assume you’ve approached Freedom Fabricators, Advanced Metal Products, and AC/DC Design and Fabrication to see who they get their steel from? Those seem to be the closest shops of any size.
Looks like Albuquerque is the closest big town, that must be the 120 mile drive?
Yeah, I know a ton of great places to get all kinds of metal near pretty much any one of those shops you mentioned, there’s just nothing where I’m actually at. Since I’m not doing it professionally it’s just not worth hiring a full truck for it, either.
Henry’s and @Knick , i did some form of a test of the citrate de-ruster’s action on mill scale. vijeo attached to show results. Description below to say what they were the results of.
I had a piece of tube that was pretty much the same surface condition as the first one in this video. Left it soaking in my own mix of the citrate de-ruster, for far longer than intended. (Planned for a few hours. Three days later i got to taking it out.)
The second tube shown is that soaked piece, hosed off (rinsing remaining black chalky powder off the surface) and dried. The purposely haphazard wire brushing by hand was to show how easily any remaining black / grey flecks come away and leave a steel surface i would call weldable.
This is light mill scale that you get on tube, with overboard treatment. But shows that chemical removal with citrate is technically possible.
Supplementary info : I de-rusted some flat bar (which has that terrible very thick mill scale type) only long enough to get rid of the rust specks it had (maybe 4 hrs). And when grinding weld areas, i noticed how brittle the mill scale was. How quickly and easily it came away, compared to typical which can seem like a ceramic glaze. I wish i had tested whether it comes away with a wire wheel on grinder.
If i’m reading the tea leaves correctly, the citrate de-ruster is :
- a mill-scale removal solution for the thin type IF one has all the time in the world for prep (days soaking).
- A pre-treatment to make heavy mill scale more easily removable by mechanical means (… IF one has all the time in the world for such multi stage prep).
I still want to test whether with enough time, even heavy mill scale will dissolve away in citrate solution.
There are of course other considerations to any treatment. Does the ‘weakening’ of mill scale soaked but not ground away weaken it’s protective function? Does one have to re-oil the remaining mill scale after welding after citrate soaking, else it rusts under the mill scale?
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I use regular white vinegar from grocery store. I use a length of ABS pipe sized to fit my cut pieces. The cut pieces slide into the ends which have screw caps. I pour the vinegar in and out at the mid point through a T joint with screw top. I find that 7-8 hours completely removes the mill scale and needs just a wipe with a paper towel.
I like that, what dia pipe did you use? This would have been a good way to go before PVC got so expensive. Thanks for sharing