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Tech: Using Oxalic acid to remove rust

Discussion in 'The Hokey Ass Message Board' started by fiat128, Mar 6, 2008.

  1. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    VERY agressive on aluminum and zinc. I have used it on corroded aluminium. I wouldn't use it on something precision, like a carb, for anything more than a very brief exposure at most.
     
  2. Leevon
    Joined: Oct 5, 2009
    Posts: 400

    Leevon
    Member
    from Nixa, MO


    Fixed it, got lazy and hot-linked from another forum I posted the pic on...should be good now.
     
  3. Tman
    Joined: Mar 2, 2001
    Posts: 34,918

    Tman
    ALLIANCE MEMBER

    Looks great!
     
  4. oj
    Joined: Jul 27, 2008
    Posts: 6,270

    oj
    Member

    Has anybody welded the metal after cleaning? It could be a boon, i tig weld and a piece of rusty metal that has a tear or crack is hell to weldup because i can't clean inside the crack/tear, maybe i could apply some of that acid to clean out the rust and then weld.
     
  5. Great info, I wonder how it would work on some of the stuff we dig up. Typically we end up soaking in mauratic till the coral is removed and we can drop in the tanks to start removing the salt. Im dealing with early 1700's shipwreck pieces that have been under salt and sand for roughly 300 years.
     
  6. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,408

    atomickustom
    Member

    Thank you, that is EXACTLY what I needed to know! You just saved a carb from certain destruction.
     
  7. mrspeedyt
    Joined: Sep 26, 2009
    Posts: 711

    mrspeedyt
    Member

    thanks for the tips!!:)
     
  8. I have a couple of front brake drum/spindles in a plastic tote filled with water and 12 oz. tub of wood bleach (got it at ACE hardware), been in there almost 24 hours, and it's still kinda pretty rusty, but there's a layer of gunk at the bottom, and white foamy stuff clinging to everything. I dumped a gallon of boiling water in on top to speed things up.... we'll see
    [​IMG]
     
    Last edited: May 12, 2011
  9. [​IMG]
    The spindles... 7 of the nuts came off with an impact no problem, kingpins took a little beating, but they came out too.
    [​IMG]
    The water probably made the stuck brake shoes worse, but a quick once over with a wire brush... and it looked good... Keep in mind this car sat in a swamp for 35 years, the i-beam was rusted clean through, and all but 3 of the lug nuts had to be torched off before it went into the goo. The cap came off with my fingers, the rod ends came out with no more than the usual effort, the kingpin retaining bolt on one came out with an impact (the other nut/stop was just flakey rust), and the cotterpins looked like they were brand new.
     
  10. stationWAGONS
    Joined: Mar 2, 2008
    Posts: 796

    stationWAGONS
    Member
    from Vegas

    Oxalic acid won't hurt original paint or chrome. too good to be true.

    Available straight in granules - on West Marine's Website.
    $10 bucks or so for a bottle that'll go a long way.
     
  11. zomb1e
    Joined: Mar 2, 2008
    Posts: 67

    zomb1e
    Member

    WOW! worked heaps better then the molass process!! thanks mister!
     
  12. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    General rule..... the more skulls and crossbones there are on a product's label, the better it works.
     
  13. Atif Naser
    Joined: Aug 18, 2014
    Posts: 5

    Atif Naser

    okay....some before and after pics...the only thin that really needed scrubbing was the rims...and that was with a SOFT toothbrush
     

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  14. Several times folks asked about neutralizing oxalic acid. After cleaning the rust off of your parts, soak them in plain clean water for a couple hours. Common household baking soda will neutralize acid very quickly. Be sure to neutralize the acid after cleaning your parts. Any active acid left in cracks or seams will continue to eat away at the metal. It will eventually eat right through clean steel.

    The yellow color mentioned is the iron oxide which has been removed from the metal. It should wash right off, or a little rubbing with steel wool or Scotchbrite will remove it.

    I've seen green color in the solution mentioned. I'd suspect that some of the parts being cleaned had some copper or brass with them. Possibly copper plating prior to chrome or zinc plating.

    As for health hazards. Don't breath the fumes. Don't let the dog drink from your bucket of acid. Don't let the kids wash their hands in it. Just use common sense as with all corrosive materials.

    If you like Rhubarb pie, you're eating a small amount of oxalic acid. Strong concentrations are found in the leaves, and considerably lesser amounts in the stalks.
     
  15. PushnFords
    Joined: Dec 2, 2011
    Posts: 52

    PushnFords
    Member

    I have a 40 gallon tub of oxalic acid I've been using for about a year on a lot of parts. It isn't working as well now and I'm getting a lot more yellow stuff on the parts when I remove it. Has anyone tried dumping in more acid into a previously used solution or do I just need to neutralize it and start with a fresh batch? With 40 gallons I'd like to refresh it if possible....
     
  16. I'd neutralize it and start a new batch. Adding more oxalic isn't going to get rid of the yellow residue.
     
  17. PushnFords
    Joined: Dec 2, 2011
    Posts: 52

    PushnFords
    Member

    I need to mix a new batch of OA and don't remember what mix ratio I used last time. After searching it seems most people recommend 1-2 heaping Tbsp per gallon of water. So:

    1 Tbsp leveled oxalic acid = 10.5 grams per: http://www.chymist.com/Mass-volume equivalents.pdf
    1 gal of water = 8.34 lb = 3782.96 grams

    So
    1 leveled Tbsp acid per 1 gal water would be: 10.5g/3782.96g = .278%
    2 leveled Tbsp acid per 1 gal water would be: 21g/3782.96g = .555%

    I'm using a dip tank with 40lbs of water in it. So according to my calculations using the figures I found for leveled tablespoons I'd need 1.85lbs of oxalic acid. BUT...all of the posts I found recommend a heaping tablespoon (not exactly an exact science) so 1.85lbs wouldn't quite be enough. If I shoot from the hip and go with 4lbs of acid per 40 gallons of water I think I'd be ok. Anyone mixed up a big batch to know how close I'm at? Shipping is high so I'd like to get enough the first order. I think I used a LOT more acid than that in the first batch so if I can dilute it and it would still work I could save a few bucks.
     
  18. Good source for oxalic acid is Amazon. Just type in oxalic acid and you get lots of hits for whatever quantity you want. I bought 10 lbs for cheap, it is great for cleaning out a rusty cooling system. In addition to some of the examples shown earlier in this thread.
     
  19. PushnFords
    Joined: Dec 2, 2011
    Posts: 52

    PushnFords
    Member

    The last batch I bought was from Van Dyke's taxidermy...I ordered baking soda at the same to neutralize it. I'll compare prices once I figure out how much to order.
     
  20. OIF1
    Joined: Dec 15, 2015
    Posts: 5

    OIF1
    Member
    from Reno, NV

    I know I'm totally resurrecting an ancient thread, but I couldn't resist posting some pictures of some bumper brackets I needed to clean up today. I love the information resources on here and really appreciate the sheer amount of knowledge everyone passes on in their posts. I've been using the info from this thread for the past 7 or 8 months and it's been a wallet saver for sure. Now instead of looking at a part for my 37 sedan and saying "nah, I'll pass on that cause it's too rusty," I'm like "hell yes I'll take that!" Now if only you guys could find a way to soak stainless trim pieces to remove dents and dings! Really though, I appreciate the great job you all have done to help each other out on here and pass that priceless knowledge on.

    Here some pics to show how great oxalic acid works (as if you needed anymore convincing): conveniently for this post, they didn't fit in the bucket all the way so you can see the same piece of metal as its own before/after.
    ImageUploadedByH.A.M.B.1470632516.329660.jpg ImageUploadedByH.A.M.B.1470632568.703094.jpg ImageUploadedByH.A.M.B.1470632698.268486.jpg ImageUploadedByH.A.M.B.1470632708.356835.jpg
     
  21. indyjps
    Joined: Feb 21, 2007
    Posts: 4,390

    indyjps
    Member

    Just ordered wood bleach from amazon. I'll be giving it a try.

    My father has used it before to strip anodizing from stainless trim at higher concentrations. IM if you want details I can find out.
     

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