Removing mill scale with hydrochloric acid?

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Anyone tried it?  My local metal supplier was out of cold rolled, so I got some 10ga hot rolled instead.  The pieces to be cleaned are 2x 3'x4' so there is no way I am wasting my time with a grinder, and I dont have a sand blaster.I did a search online and saw a few places where people had used muriatic acid (HCl) to remove the mill scale.  I dont have want to make a huge dip tank, so I am thinking of mixing up some acid and water 1:5 and putting it in a spray bottle and rubbing it in and letting it sit for a few min.  We have a pool so I already have the acid on hand.Does this sound like a decent idea?  I think I will test it out first on a piece of scrap.Probably put in my respirator and some rubber gloves and see what happens.
Reply:Be careful....eyes, lungs and skin...It'll work..yes, I've done it..be careful...use it full strength, let it sit a couple hours....rinse, repeat as needed...after, it will rust as you watch---be careful...
Reply:I've used muriatic acid on small parts....it eats right through mill scale.  Took about 20 minutes.Pay heed to TEK's advice.  This stuff is nasty.  It formed a yellowish/greenish vapor cloud in the sst bowl I used and I got a whiff of it and it was not pleasant at all.I've never sprayed it but I'd be worried about what it would do to the innards of the sprayer.  You also mentioned mixing it with water.  There's a method for mixing acid and water safely so that it doesn't boil up in your face.  I don't remember which it is...pour the acid into water or pout the water into the acid...but I'd sure find out if I was doing this. Also, use it outdoors away from entrance doors and walkways.  Those fumes travel.  They're not only harmful to people (AND PETS) but will also corrode any metal they can find...machine tools, wiring, paint cans, everything!  And it doesn't require direct contact either...the metal just needs to be exposed to  the fumes.Did I mention....please be careful.Hope I didn't sound preachy....just concerned.Miller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:I use a mix od muradic acid to clean old fuel tanks in my garden tractors. BE CAREFUL, as I wasnt and someone now owns a pick up truck where the vapor took the paint of it! I new it was strong, but not that strong. I was working about 5 ft away from my truck listning to the radio.Id hate to thin what it will do to your skin, eyes and lungs.
Reply:it can be used I have not been on the east coast for years, but here in the W.C it can actually be used to wash over the road trailers when super dirty.  it would be a mix of 3 to 1 and you want to pour the acid into the water, do it slow and try and keep it away from any cement or keep the cement super wet with water.  To neutralize the acid wash you want to rinse with 3 times the amount of water to rid the metal of all the acid.  This process also works well to remove galvanizing from metal before welding as well.Ron
Reply:Thanks for the info guys, I was hoping that some other people had used it and that it would work!  You guys are right about the safety concerns.  It can be pretty nasty stuff, especially in an enclosed environment, the vapors are super acidic.I am actually a chemist, so I know all to well what can happen with this stuff if you are not careful, I just didnt know exactly what the mill scale was made of to figure out if it would react with it or not.BTD:The correct way of diluting a strong acid it to add the concentrated acid to water slowly (you would be suprized how much heat is given off, and the reason for doing it slowly is so that it does not boil the water you are adding it to).  The reason that it is done this way is that if you do the opposite you can actually instantly boil the water that you are adding and then the acid mix can boil over real quick and shoot all over you.I had an accident in the lab where semi concentrated acid shot all over my pants and had a nice rash for about a week all over one of my legs.I was planning on doing this in our side yard away from everything where there should not be any problems.  I will def wear my respirator as burnt lungs just hurt.
Reply:I use Muriatic on metal for a lot of my sculptures. Use it full strength. Use a cotton rag to apply. Spraying isn't good as it floats and will corrode most things it lands on.Plus it trashes the spray bottle.In my experience, not all mill scale is created equally. Some comes off easy while other scale is like bomb-proof unobtanium!!!!! Apply liberally and repeat each hour as necessary. Don't forget to keep a 20gal, bucket of water mixed with baking soda to neutralize in case of a bad splash.200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:i used to use it(muriatic acid) 3 gallons at a time in a pump up sprayer to etch concrete shop floors. the mechanics never figured out how we got the floors so clean. we had to keep the floors wet the entire time, and used a neutralizer that we got from a janitorial supply house.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:Have plenty of baking soda on hand.  Wear thick gloves, cover all your skin and use a face shield.  Ventilation is important, too.I used sulfuric acid on a 1" plate bench top.  It can be purchased at a plumbing supply store for about ten bucks.Be careful.Jack OlsenMy garage website
Reply:it was 5 bucks a gallon last time i bought at lowes in the paint departmentDynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:I would degrease first with a base such as ammonia or lye (NaOH).If there's any grease or oil on top of the mill scale, it will protect or shield it from the acid. So...degrease first, then rinse, then use acid.