Phosphoric acid to clean heat exchanger.

Discussion in 'Diesel Engines' started by Roly, Sep 25, 2010.

  1. Roly
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    Roly Senior Member

    Does anyone know the dilution ratio for phosphoric acid to clean the raw water side of a heat exchanger or do I use it neat?
    I have pulled the heat exchanger/exhaust manifold on a Yanmar 3GM30F and are going to bath it in H"x"PO4.

    Is there a good product for decarbing the exhaust manifold insides? Or is it better to do it with an abrasive at a
    a reconditioning shop?
    Any advice from the experienced, much appreciated.
     
  2. mcollins07
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    mcollins07 Senior Member

    Roly,
    I used a product called CLR to clean my heat exchangers. I rinsed very well after running the engine up to operating temperature with it circulating.

    phosphoric acid comes in different concentrations. No one can really comment on how much to dilute it without knowing the starting concentration. Phosphoric acid, in a concentrated form, could be dangerous to a heat exchanger. A safer approach would be something like oxalic acid. You still want it diluted but it is not as strong an acid, thus concentration is a little less critical.

    I have not tried to clean exhaust manifolds.

    ~ Michael
     
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  3. mydauphin
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    mydauphin Senior Member

    Ditto on Oxalic acid. I buy a product called Rust aid used to take rust out of sprinklers, it is mild enough to leave in there for an hour. Oxalic rinses off very well with plain water
     
  4. CDK
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    CDK retired engineer

    Phosphoric acid in commercial rust removers have concentrations below 12% for hardware store products or 5% for household products.

    To use this in a heat exchanger doesn't make sense to me, unless the exchanger is made from steel and you want to remove rust. I would use 20% hydrochloric acid to remove lime deposits and flush with lots of water as soon as the acid stops foaming.

    Carbon deposits can be easily removed with a high pressure cleaner and a wet blasting accessory.
     
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  5. Roly
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    Roly Senior Member

    Thanks everyone for your comments.
    I have heard about the use of Lye but didn't want to go that extreme.
    The Phosphoric application I got from Woodenboat forum (Detroit diesel) & they
    prefer it over the lye but didn't give the final dilution. It is the weekend
    and I am committed to do this today. Tomorrow it goes to the machine shop to get the
    mixing flange milled flat.
    Anyway it did the job well fizzing all the lime off in no time.
    I've got it soaking in fresh water now with mild bicarb to make sure all the acid has gone.
    http://forum.woodenboat.com/showthread.php?3295-heat-exchanger-cleaning
    Unfortunately I also lent out my tub of Oxalic acid & can't remember who I lent it to!
    Time for a lend book.
     
  6. Roly
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    Roly Senior Member

    Update.
    On removing the lime with phosphoric I managed to remove the heat exchanger tube assembly from the cast iron manifold.
    The bronze/Cu/brass (?) tube assembly is installed in an Al tube!
    Through the port it looked like stainless.
    Hydrochloric sure as hell would not have been good on that.
    The Al tube is not removable.
    I guess if you pump the HCl solution thru, in situ,(without pulling the H.E.) it may not be a problem as the "O" rings should keep the solution on the raw water side.
     
  7. Jelle
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    Jelle New Member

    Phosphoric acid is one of the main ingredients in cola (I kid you not), so I would just pour in a bottle or two. That is something the stuff is good for, otherwise someone might drink it accidentally. :)
     
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  8. CDK
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    CDK retired engineer

    Wrong, cola contains only trace amounts (<0.1%) of H2[HPO3], much weaker than phosphoric acid (H2PO4). Good to prepare a tender steak if you marinate it a couple of hours, useless to remove rust.
     
  9. kenJ
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    kenJ Senior Member

    It's a good idea to read the labels before you use any of these products. Because of the heat transfer and ease of manufacture, most heat exchangers have copper tubes inside some sort of metal case. CLR states on the label not to use on copper. A couple products that are safe are Lime Away and RydLye. I know several folks that will pour a bottle of Lime Away into the HX at least once a year, let it set for several hours then reattach the raw water cooling lines and flush out.
     
  10. Jelle
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    Jelle New Member


  11. gonzo
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    gonzo Senior Member

    Wiki is not a reliable source.
     
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