Ain't that spiffy!! Butt🍑, what about large sheet steel. 24 hour vinegar soak on a 4×8 sheet? Come on, get real. How do you do that???? Everything is possible in miniature, but what about the real world!!

we have a problem when removing rust with acid and welding stuff together, after paint job and out in the weather it start to rust from inside out - any tips?

Holy crap, thank you This has been bugging me for years.

you can use phosphoric acid (rust converter) if you have a large sheet put a good wet layer of phosphoric acid then cover it with cling film to syop it drying out. it will lift or dissolve the millscale in around half an hour and you can rinse it off and the steel won't rust straight away.

Purchasing HRPO for those thicknesses where HRPO is available is worth every penny imo.

Thank you for sharing your knowledge!

High strength industrial or cleaning vinegar for light rust/scale and Muriatic acid for heavy scale/rust.

At PK Harris yard at Appledore the workforce were directed to urinate into the 45 gall oil drum supplied. This was splashed on the steel plates, and wire brushed off the following day.

im gonna try this for sure

That water on the bar is water thats coming from the propane flame. It’s condensing on the colder metal, and disappears when the metal heats up. Burning fossil fuels produces water, among other things. Look it up.

Useful video. I have a tub of vinegar with a sealed lid that I use for removing rust. Vinegar is especially good at cleaning rusty chain and I use a product made by Abrasive Media Supplies, made here in Australia, called Abrasive Blasting Rust Inhibitor. You mix with water at about 200:1 and it stops it rusting. They say it gives 72 hours protection but I’ve parts sitting for months now with still no rust. I actually got the product because I have my own sandblaster but it works well on parts that have been cleaned in vinegar.

You can buy even stronger vinegar for agricultural purposes if you can find it.

Great Tip, Thank you! I'm working with some new 3/16" sheet metal now that I have to clean, and I was going to sand blast it....but now I'm going to use a mild muriatic acid solution (because that what I have on hand) and give that a try.

Phosphoric Acid? Have used this a fair amount. (HCL is awful.) There are special “mill-scale” grinding disks. They’re a fair bit each, and hard(er) to find. Bought some a while back.

The moisture is a byproduct of burning propane and it is condensing on the cool steel, that moisture you see on the steel is not coming out of the steel, you are putting it there.

The "paint stripper" pads that fit an angle grinder are great at removing mill scale and leaving bright clean metal. No scratching like flap discs and faster than vinegar. I do use vinegar for removing zinc from nuts and other things prior to welding. I mostly TIG weld, so the cleaner the better.

I'm not sure about white vinegar, but at the steel mill, they pickle it starts first going through a heated acid bath, so heating the vinegar may speed up the process.

Good work mate. Mill scale is essentially "magnetite" or Fe3O4. The red rust you normally get on bare steel is "heamatite" or Fe2O3 (that's the one they mine in the Pilbara...) Mixing with acid essentially makes FeCl or FeS (iron and chlorine, or iron and sulphur compounds) and water. I have heard of some blacksmiths using the mill scale or black scale as a sort of flux, but I can't remember exactly how or what. Might be worth me revisiting that... Also

The oxides form mainly at red heat temperatures , nothing to do with cooling at all. Otherwise mill scale would form at ambient temperatures instead of rust , which is a different , hydrated , oxide The hotter the metal is , the faster oxides form , right up to the point where the iron combusts if there is enough oxygen. The best way to remove mill scale is to use hydrochloric acid , as long as you monitor the process and remove the item as soon as the scale is gone.

That is not micro moisture. It is moisture in the air. You crossed the dew point😂😂

You might try citric acid, bought as a powder, mix up the strength you need. Quite a bit cheaper than vinegar

The torch is only producing visible condensation from cold to hot. To reduce flash oxidation “rust “ wipe with oil then degrease before weld. “

the moisture you're seeing is being caused by the gas torch. the byproducts of hydrocarbon burning are co2 and h2o. it's too hard to do the chemical equations in a YT comment so you'll have to take my word for it or go google it. that said, acids do remove mill scale and flash rusting will occur on bare steel. i prefer phosphoric acid to remove mill scale because it's faster than acetic acid (vinegar) but far less aggressive than HCL and it leaves a thin layer of phosphate salt on the steel than inhibits rusting. it's not as dangerous as other acids but it works in minutes rather than hours. it's also cheap and easily available. don't listen to the people in the comments talking about hydrogen embrittlement and various other myths. they are full of themselves like many very young welders are. hydrogen embrittlement only occurs on higher strength alloy steels, not mild steel like A36 and it usually occurs from the FLUX entraining moisture, not the metal of the electrode rod itself or steel you're welding getting wet or being treated with acid.

Mill scale is extremely brittle. We used to dispose of 500kg≈1000lb a month of it. In order to get the right diameter wire to produce fasteners we had to draw it and pas it through a die. Of course we shouldn’t run the mill scale through the die so what we did was to pass the wires through a system of pulleys so they break that nasty waste. Of course we didn’t have a machine large enough to do the same with round bars so we had 8m tubes; one with sulfuric acid, one with water to rinse and a third one with caustic soda solution. Now that I’m retired this method is fantastic because I usually don’t have to use the material right away.

If you rinse with baking soda it will not rust much one tablespoon to gallon water

A similar performing alternative is citric acid (it is slow too) - with the benefit it does not stink up the whole shop. Available as a powder, you can find it online, or at pharmacy, or soap making supply stores. One comment below about hydrogen embrittlement I thought was interesting, is the hydrogen coming from water in the soaking & rinsing & cleaning, or from the acid, or from the flame drying as combustion produces water? Or all of them? And how bad is the hydrogen embrittlement? If the part is just being machined I don't know if there is much of an issue, but if it needs to be welded then this could be a problem with the approach.

L That was interesting to me as very amateur model engineer as have be told hot roll steel stay straight when working on it than bright mild steel, but the mill scale has been a problem to remove, thanks

Your pipes are going to hate you.

I didn't see any mill scale being removed, only rust. Acetic acid etches ferrous surfaces, but I guess if you're doing art you don't care. In the real world of metal working, that matters.

Mega, thanks.

The moisture you are seeing on the surface of the bar when heating with the torch is condensation of water vapor which is present in the combustion gases. Try heating the bar with a hot air gun and you will see no moisture on the surface of the bar. That said, I do agree that there is moisture trapped in the surface of the bar and without heating the bar will definitely rust in short order. I generally just rinse the steel using hot water then wipe dry. It is dry immediately and I am headed to the saw or welding table. Great tip using vinegar, I have been using Muriatic acid for over 30 years but will start using vinegar for some things.

I like the flame drying, wouldn't have thought of that

cool tip thanks

Definitely use it, so you can cause hydrogen embrittlement. Job security.

I use 20%. Never tried stronger. Mine is mainly for rusty steel plates i use for making targets. I have a tub i place them in and fill with water. Probably 15 gallons in size. Put the top on and leave a day or two.

Works better if you degrease first. I use acetone.

Cool sculpture! Good trick with patinaing with rust

Thanks for the tip about using vinegar, I had heard of using vinegar to clean galvanized metal but never of it removing mill scale. Thats very helpful information! I actually used some muriatic acid today to remove the zinc from some hold down clamps I was preparing to weld to a fixture I was making. Phew, do not breath anywhere near that, it's deadly! I live in Oregon where the humidity is often above 95% as it currently is so i don't think the heating metal to remove moisture trick will work for me in the winter but still good to know if I had a heated shop. I appreciate the video, thanks.