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  1. #16
    BobL is online now Member: Blue and white apron brigade
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    If it was hydrofluoric I would leave it well alone. That stuff permeates skin, fat and muscle to give you a bad burn and doesn't stop until it hits something with Ca in it like bone and then turns it to jelly.

    I have heard of an electrochemical cleaning formula for SS that use salt, and H2SO4, HCl, HNO3 acids, and another one is HCl, HNO3 and H3PO4, usually done at elevated temperatures for short period or risk serious etching. The solutions are usually quite concentrated and viscous.

    My understanding is the workpiece is the opposite to rust removal ie with and put onto the anode (+). The polishing process removes ~50 microns of SS from the surface and levels peaks and valleys.

    Because concentrated acid baths are inherently dangerous and expensive especially for large objects, portable units that use concentrated citric acid painted on using a carbon fibre brush connected to a high current power supply and the work at ground are increasingly being used. The electrical discharge heats the acid and dissolves the scale etc. Commercial units are available but have also seen you tube vids showing a welder being used as a power supply. I have been meaning to try this for some time.

  2. #17
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    Quote Originally Posted by BobL View Post
    If it was hydrofluoric I would leave it well alone. That stuff permeates skin, fat and muscle to give you a bad burn and doesn't stop until it hits something with Ca in it like bone and then turns it to jelly.
    That's why I want to avoid the use of pickling paste where possible. I use chemical gloves and a full face shield whenever I use the stuff and I still don't like it!


    I have heard of an electrochemical cleaning formula for SS that use salt, and H2SO4, HCl, HNO3 acids, and another one is HCl, HNO3 and H3PO4, usually done at elevated temperatures for short period or risk serious etching. The solutions are usually quite concentrated and viscous.

    My understanding is the workpiece is the opposite to rust removal ie with and put onto the anode (+). The polishing process removes ~50 microns of SS from the surface and levels peaks and valleys.

    Because concentrated acid baths are inherently dangerous and expensive especially for large objects, portable units that use concentrated citric acid painted on using a carbon fibre brush connected to a high current power supply and the work at ground are increasingly being used. The electrical discharge heats the acid and dissolves the scale etc. Commercial units are available but have also seen you tube vids showing a welder being used as a power supply. I have been meaning to try this for some time.
    When we had the work done some time ago, the local electroplater couldn't have been less interested, so we enlisted the services of a carburettor rebuilder of all things. He had a smallish setup for plating carbys and using a different solution was able to electropolish our stainless bits. Not being the boss, I never did find out what was used.
    More research required.

  3. #18
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by Karl Robbers View Post
    When we had the work done some time ago, the local electroplater couldn't have been less interested, so we enlisted the services of a carburettor rebuilder of all things. He had a smallish setup for plating carbys and using a different solution was able to electropolish our stainless bits. Not being the boss, I never did find out what was used.
    More research required.
    Why don't you put a Scotchbrite cleaned piece of SS into your electrolysis bath and see what happens - remember it has to go on the + terminal side.
    Normally its done with warm-hot (75șC) bath but it only takes minutes using the conc acid baths but it might still work albeit much slower at room temp and with the foot bath salts electrolyte.

    BTW I've ordered some carbon Fibre brushes to try the paint on method.

  4. #19
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    It's been a while since I used it and I'm not at home at the moment to verify, but a method I got of the interweb a few years ago for cleaning stainless welds used a solution made up of phosphoric acid and ethelyne glycol (rust eater and antifreeze).
    To use, clip one lead of your battery charger to the piece to be cleaned and a balled up piece of clean rag (say 20mm diameter) to the other lead. Dip the rag into the solution so it's saturated then slowly rub it back and forth over the area to be cleaned. It gets quite warm and may crackle a little bit but after a few passes the welds come up a lot cleaner.
    Unfortunately I can't remember the ratio of the solution or the polarity of the connections but the chemicals involved are fairly innocuous and it achieved the results I was after.
    If you search google or YouTube for electro cleaning stainless steel, you should be able to find more info. I believe there are commercially available kits for this with conductive brushes etc but for the occasional one off job this process worked pretty well.
    Apologies for the vagueness but hopefully this might point you in the rough direction of a solution.
    Cheers,
    Greg.

  5. #20
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by kwijibo99 View Post
    It's been a while since I used it and I'm not at home at the moment to verify, but a method I got of the interweb a few years ago for cleaning stainless welds used a solution made up of phosphoric acid and ethelyne glycol (rust eater and antifreeze).
    To use, clip one lead of your battery charger to the piece to be cleaned and a balled up piece of clean rag )say 20mm diameter) to the other lead. Dip the rag into the solution so it's saturated then slowly rub it back and forth over the area to be cleaned. It gets quite warm and may crackle a little bit but after a few passes the welds come up a lot cleaner. .
    This is more or less the method I described above using a carbon fibre brush and citric acid. When I get my brush I'll give it a crack.

  6. #21
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    Quote Originally Posted by Karl Robbers View Post
    What electrolyte could/would one use to chemically polish stainless steel? I got some fittings done once after I had fabricated them and the finish was brilliant, certainly not a mirror polish, but the electrolysis removed the scale and discolouration off the weld without leaving the washed out look that pickling paste, (hydrofluoric and nitric acid I believe) gives. I would love to be able to perform this in house and hopefully avoid the use of pickling paste where I can.
    Citric acid or oxylic acid. Citric is better as its food grade. Used to use it to electro-polish smallish stainless parts when i worked in food industry. A lot safer than pickling paste. Avoid using stainless as the anode releases cadmium. use carbon rods or welding supply places sell carbon brushes for similar purpose.

  7. #22
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    I've also had great results with rust removal using basically the set up in the first post.

    Has anyone tried electrolysis for removal of mill scale from mild steel?

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