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Technical Muriatic Acid Question

Discussion in 'The Hokey Ass Message Board' started by CarQuestions, May 14, 2020.

  1. CarQuestions
    Joined: May 24, 2015
    Posts: 85

    CarQuestions

    I cleaned some box steel with muriatic acid so as to clean off the mill scale. The parts will be used for a welding table.

    Working outside I poured the acid straight (not diluted) into a small container and used a foam brush to smear the acid onto the metal and then used a scotch bright pad with the acid to rub off the black and surface rust. I then only sprayed down the parts with water...now is there a next step???

    Other than rinsing with water is there any other other cleaning/neutralizing I need to do?

    Yes I read on line to make sure to put the cap on the bottle and not have any acid/ brushes in my metal building...

    THANKS!!!
     
  2. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,175

    Jmountainjr
    ALLIANCE MEMBER

    In many cases baking soda and water is used as an after treatment to neutralize an acid wash. I like to use pickled and oiled steel to avoid all the mill scale.
     
    Last edited: May 14, 2020
  3. Boryca
    Joined: Jul 18, 2011
    Posts: 663

    Boryca
    ALLIANCE MEMBER
    from Detroit

    Only thing you need to do is protect it to keep it from flash rusting now that it's all clean. WD40 in large quantities is great for that.
     
  4. Rand Man
    Joined: Aug 23, 2004
    Posts: 3,497

    Rand Man
    Member

    I’ve used acid on parts before, and the amount work needed in the cleanup makes me think I should just used soap and water in the first place. Also, I didn’t have the lid on tight. Rusted up everything that shelf, including the shelf. Never gonna try acid again man.
     
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  5. CarQuestions
    Joined: May 24, 2015
    Posts: 85

    CarQuestions

    THANKS guys for your help!!!

    I will start a different thread on metal prep.
     
  6. indyjps
    Joined: Feb 21, 2007
    Posts: 3,881

    indyjps
    Member

    Baking soda is common to neutralize. Actually dish and laundry soaps are basic on PH scale, as long as its a weak or very diluted acid (rinsed) the soap will neutralize.
    Rust protection is on you.
     
  7. Los_Control
    Joined: Oct 7, 2016
    Posts: 694

    Los_Control
    Member
    from TX

    I had the same experience. Yeah it does remove the rust and does a great job of it. Same time it caused rust on all my tools hanging on the wall, my 12" dewalt chop saw, anything in the garage ... and I believe it was leaking through the cap, since I did screw it back on.
    And because it was not neutralized properly. my fenders quickly rusted again. Even though I did follow directions. One fender did while other did not.
    IMHO, the muratic acid is just to unstable and I prefer to not use it.
     
  8. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,261

    56sedandelivery
    ALLIANCE MEMBER

    Several precautions to take with Muriatic acid. First of all, always use it outside. Don't smoke or use any power tools around the fumes (volatile/explosive!). Store it outside, and away from everything/anything. It will remove galvanized coatings. Neutralize with baking soda, and hot water, so the part dries quickly, then get it in paint or oiled down. Always work "upwind" with it to avoid the fumes as much as possible. I used to use it all the time, but I have't had any real need lately. And now, a STORY: I have told this before here on the HAMB. My Mother had a couple of moles at her house in the yard, and I did everything to get rid of them. Then, I decided to give Muriatic acid a try. I figured the fumes would get them. The moles were just outside of her yard, on the other side of a hedge. I assembled an "apparatus" starting with a shop vac to blow the fumes into the moles burrows. Used an old Clorox bleach bottle, and plugged a hose I got from work (something I got from one of the Respiratory Therapists). Then I took a short piece of PVC pipe and glued it to the side of the Clorox bottle. Tossed a bunch of rusty metal, bolts, nuts, washers, and some galvanized metal I had laying around, into the Clorox bottle. I snaked the top hose through the hedge, and into the mole burrow, plugged the shop vac into the side port, put some Muriatic acid into the bottle, and then realized, the shop vac was on the other side of the hedge, so I ran down the 50 feet to the end of the hedge, and back up the other sides 50 feet, and hit the switch. I knew I messed up in that nano-second of time hitting the switch. The fumes had backed up into the shop vac, and when I hit the switch, B-O-O-M!!!!! Blew the top off the shop vac, and Mom's neighbors were looking out their windows to see what was going on. I thought I had it all planned out pretty good, I just messed up on where I had the shop vac. Like I said, the fumes are explosive. It was a Craftsman shop vac with the heavy plastic top, and the four tabs to keep the lid on. The tabs had broken off many years earlier, and that probably saved my bacon; it only blew the top off and not blown up the whole shop vac. And, Mom still had moles. I am Butch/56sedandelivery.
     
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  9. Ericnova72
    Joined: May 1, 2007
    Posts: 403

    Ericnova72
    Member

    Look into using Citric Acid, same stuff as used for food preservative, buy it as a powder.. There are a couple threads on the HAMB about it.
    Much milder and environmentally friendly....low cost too. Works really well, but not nearly as fast acting.
     
    irishsteve likes this.
  10. raven
    Joined: Aug 19, 2002
    Posts: 4,619

    raven
    Member

    Why not use citric acid? Seems to do the trick without as much danger.
    r


    Sent from my iPhone using H.A.M.B.
     
    irishsteve likes this.
  11. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,261

    56sedandelivery
    ALLIANCE MEMBER

    I've been using Evap-O-Rust (I think that's the spelling) recently. NO smell or acrid fumes, and you won't blow yourself up. Seems to work really well on the small parts I've done lately. It is expensive however. I also still have a 5 gallon container of molasses. Have't tried citric acid, and i quit using the hand operated, wire brush years ago.
    I am Butch/56sedandelivery.
     
  12. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,528

    2OLD2FAST
    Member
    from illinois

    No one has mentioned Naval Jelly which I'm pretty sure is phosphoric acid , rinse with water , leaves a paintable coating that doesn't flash rust , used to be marketed as metal etch . Is this not still used. ??
     
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  13. bschwoeble
    Joined: Oct 20, 2008
    Posts: 562

    bschwoeble
    Member

    Citric Acid. It doesn't matter how long you leave the part in, unlike muriatic acid. It will go stale after derusting many parts. I really got to hating the smell of molasses. If you use citric acid, don't get it on your clothes, permanent yellow stain. Worked great on my deuce pickup roof that submerged.
     
  14. spanners
    Joined: Feb 24, 2009
    Posts: 944

    spanners
    Member

    We used diluted Muriatic acid (50/50 with water) in the panel shops. It was specifically used to treat surface rust areas around front and rear screen openings prior to painting. You rub it into the rusty areas using steel wool or scotch pads and then wipe down with a wet rag. Blow dry with compressed air and prime and paint. When you dry it off the rust areas go a black/purple colour. The product name over here was Deoxideine (I think I spelt that right).
     
  15. Rand Man
    Joined: Aug 23, 2004
    Posts: 3,497

    Rand Man
    Member

    Yes, phosphoric acid is the right stuff. I worked in manufacturing in the past, and we used that in the paint line pre-wash. Those parts would not rust for weeks if for some reason they couldn’t be painted/powder coat right away.
     
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  16. rusty valley
    Joined: Oct 25, 2014
    Posts: 1,659

    rusty valley
    Member

    i too had a gallon jug of it in the shop, with the cap screwed on tight, and everything within 10 feet of it got rusty
     
    Los_Control likes this.
  17. noboD
    Joined: Jan 29, 2004
    Posts: 7,227

    noboD
    Member

    Jmountainjr, I remember the term pickled from a year in a sheet metal shop a lifetime ago, but what is it pickled in? I remember the metal not having any scale which was nice and what the OP is looking for. Thanks.
     
  18. It was likely pickled in Hydrochloric Acid, but it's done at high temperature, 180F, then rinsed with hot water, twice with an inhibitor added at the last process. It's then dried with a hot air blast.
    At least that's how we did in our mill.
     
  19. Los_Control
    Joined: Oct 7, 2016
    Posts: 694

    Los_Control
    Member
    from TX

    Think I should share, the muriatic acid works awesome. If you look at my avatar and then here is a fender after using the acid. Because I do not know any better, My new plan ... parts I can remove and take care of on saw horses in the back yard away from everything, Bed sides are coming next.
    Because of the cab, and everything involved, doors, window regulators, cables etc ... I am not going to get the acid near it.
    Same time acid is the only thing I found that will cut the rust. Trying to sand it seems like it only polishes the rust and not remove it. A learning process. IMG_20191015_141001611.jpg

    Here is a photo of collateral damage. This saw has low mileage and still on original blade.
    You can see the rust on it from the acid being in the shop. And I have same issues with new screwdriver, wrenches etc...
    IMG_20191015_141001611.jpg 0515201211.jpg
    Sorry for double image, not sure how to correct it
     
  20. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,175

    Jmountainjr
    ALLIANCE MEMBER

    Algoma56 probably has it correct about the mill process used to make pickled and oiled steel. All I know is that when buying steel to make parts I like P&O much better that cold rolled. A machine / fab shop guy I know got me using it a while back and it's all that I use now.
     
  21. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,260

    F-ONE
    Member
    from Alabama

    I’m not a chemist so keep this in mind....

    I have heard that muriatic acid is about the worst stuff you can use to de-rust anything you care about.

    I read that muriatic acid chlorinates iron or steel.
    Basically it chemically bonds chlorine into the metal. Chlorine is an oxidizer. Oxidizers rust metal.

    Look at it like an anti-virus program that destroys your computer.

    It works fast though.

    Do I know for sure it chlorinates steel?
    No.
    What I do know is anything I tried the stuff on.....
    eventually turned to poo poo. Although it did look good.....
    for a little while.

    I cleaned a water pump pulley in vinegar 10 years ago. After I wiped it off I sprayed WD on it and forgot about it.
    It still looks like it did the day I sprayed with WD 40.
    If it had been muriatic acid instead of vinegar, that pulley would look like a dug Civil War relic.

    The above would explain why anything I used the stuff on looked really swell and then crumbled like saltine cracker 3 months later.

    Yes I did rinse repeatedly and use baking soda....
     
  22. BrerHair
    Joined: Jan 30, 2007
    Posts: 4,446

    BrerHair
    ALLIANCE MEMBER

    Oh god that’s rich! Beautiful
     
  23. indyjps
    Joined: Feb 21, 2007
    Posts: 3,881

    indyjps
    Member

  24. Shutter Speed
    Joined: Feb 2, 2017
    Posts: 823

    Shutter Speed
    ALLIANCE MEMBER

    I hope you keep your muriatic acid in a glass Reagent bottle, and heed ALL warnings.

    I’ve used it to “antique” hardware on furniture reproductions. Guess it will antique your ride.
     

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