Caustic soda dip tank

Discussion in 'Workshop Projects' started by davieh3350, Feb 5, 2017.

  1. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    Today in my shed... I have been making a dip tank for cleaning off rust, paint, grease and dirt from bits of machines. image.jpg It's just an old oil tank with the top hacked off, the drain holes blocked off, the bracing inside removed and a rib fitted round to stop it bellying out. Nothing special...

    This is a sewage pump that I had to repair. image.jpg The pump sat in a bucket of caustic soda/water mix for a few days, taken out and rinsed off, dried and then given a light wire brush, 10 seconds worth.
    It eats grease, oil, paint, rust and dirt, skin and eyes, so you need to wear goggles and gloves and waterproofs and keep kids and animals well away. It doesn't touch iron based metal, but eats copper based alloys. Aluminium is not to go in at all, it dissolves quickly and it releases hydrogen gas which could go with a bang.

    I've only started using it, played a little with the caustic/water ratio and heating it, but I think it's great stuff (again, treating it with respect)
    Has anyone else used it?
     
    Greenbeast likes this.
  2. burr elm

    burr elm Member

    Location:
    Bedfordshire
    You want a wire basket and block and tackle to raise/lower into tank.
     
    Greenbeast likes this.
  3. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    Yes, don't want to start splashing bits in and out. I could fit a swinging arm on to the middle rib and at the top and swivel it round by hand.
     
  4. burr elm

    burr elm Member

    Location:
    Bedfordshire
    If you strip any wood such as doors you want plenty of vinegar or other mild acid to kill the caustic after you have washed it down with water.
     
  5. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    A bottle of vinegar sits beside the tank in case of it getting on the skin.

    Never used it on wood, got to be pretty strong mix so that you're not soaking the wood for too long, it eats some of the old type glues, or so I've read.
     
  6. burr elm

    burr elm Member

    Location:
    Bedfordshire
    Any glue containing animal parts (hoof).
     
  7. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    Luckily all my bits I plan to dip are metal based glue!
    Do you use caustic soda?
     
  8. burr elm

    burr elm Member

    Location:
    Bedfordshire
    No a friend had a large tank that he used for stripping doors years ago.Tank was hot not warm, used to load tank overnight and power wash next morning.
     
  9. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    I had a gas ring under a smaller tank, it was boiling, fairly moved the paint! think it's every ten degrees rise in temp halves the time it takes.
    Do you know the ratio of caustic to water that he used?
     
  10. burr elm

    burr elm Member

    Location:
    Bedfordshire
    I would be inclined to say boiling is a bit ott when you think about what you are breathing in :nailbiting::nailbiting::nailbiting:.
    Ratio of caustic/water i have no idea, water was very pale milky colour, however that could be down to paint particles.
     
  11. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    Think boiling was too hot, just by the amount of gas it used!
    I think when you mix it at the start is when you need to watch for gas coming off.
    I'm going to put 1000 litres in the tank along with 75 kg of caustic and see how that does for a start. Water in first though!
     
  12. tinman

    tinman Member

    Location:
    Ulster
    would you not consider electrolysis a better and safer way to remove the rust.
    i like to stay away as far as possible from anything acid like tbh.

    mr rucker here explains it, all be it over a half hour but you can see the results.
     
    Cowcalf and crofter 65 like this.
  13. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    Looked a little at electrolysis, but going down this route as it's so simple, mix it up, put the bits in and walk away, the stuff I'm doing isn't needed ASAP. It doesn't eat away at the iron either, so if I left it for a month it wouldn't matter.
    it's safe enough if you are careful, the strengths I was using doesn't lift your skin on contact.
    Leaves the metal fairly rustproof for a fair while too.
     
  14. Exfarmer

    Exfarmer Member

    Location:
    Bury St Edmunds
    Just be very careful, it is the way to get rid of a body!
     
  15. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    I'll remember that as I'm perched on the top trying to reach down for the bit just out of reach...

    There was a lad in South America who done hundreds for a drug gang.
     
  16. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    Forgot I'd started this thread. image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg A quick wire brush and it's back to bare metal.
     
  17. tinman

    tinman Member

    Location:
    Ulster
    would it not eat away that strap?

    long time ago since i was round the caustic baths, used to work in a factory where we dipped molds into a caustic bath and then a hot water bath to rinse it and then into a sand blaster for a clean, used it to remove rubber residue on injection molds.
     
  18. davieh3350

    davieh3350 Member

    Location:
    Pitlochry
    No, doesn't eat away at them.

    Pressure washer is fecked:(, it would just blow the stuff away without needing to scrub it, though at least scrubbing at it you notice little things that you wouldn't see 5 foot away.
     
  19. tomlad

    tomlad Member

    Location:
    nr. preston
    Im told a citric acid dip does symular

    I couldn't source powdered citric acid
     
  20. laich

    laich Member

    You get it on ,Amazon or ebay. Or food wholesalers. Type in citric acid and it will come up. It is not expensive, I bought a 5 kg tub for about £20. It will remove rust from steel /iron , but will not remove paint or oil/grease.
     
    tomlad likes this.

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