Announcement

Collapse
No announcement yet.

Electropolishing not what I expected

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Electropolishing not what I expected

    I made up a solution of 25% sulphuric battery acid and 75% phosphoric acid. I connected a stainless steel boat vent cap to a DC power supply consisting of a variac transformer feeding a 120vac to 12vac transformer to a full wave bridge rectifier end in battery clips.

    The diode bridge got pretty hot quickly which was surprising as I adjusted the variac to put out just 5 amps. The solution bubbled and after an hour the part was dull not shiny as I was expecting so I turned it on again and forgot about for about 5 more hours.

    See how nice and shiny it came out? WTF!!!
    You may only view thumbnails in this gallery. This gallery has 1 photos.

  • #2
    You done shined the bollox of of that, never mind, if you get a stuck bolt in an engine you can remove the engine from around the bolt
    mark

    Comment


    • #3
      You did not mention which polarity you set your part to...
      "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

      Comment


      • #4
        Electropolishing requires just the right current density and a bunch of chemicals, not just 2 acids of unknown concentration and a battery charger

        Comment


        • #5
          I tried this using my tig welder. I got an amazingly beautiful matt finish to my workpiece . I think it needs a fine balance of the right chemicals and power to knock off the high spots on your workpiece. Hope you get it right . I have a use for this and it would save me alot of mechanical polishing.

          Comment


          • #6
            I use water with table salt and 6 Vdc to etch some images onto stainless steel plates. It only takes a few minutes to remove 0,2 mm of metal around the artwork screen. 😉 Acid and several hours would mage the plate disappear also.
            Helder Ferreira
            Setubal, Portugal

            Comment


            • #7
              You can get the same results you did with a grinder and a flap wheel in less than five minutes.

              I just need one more tool,just one!

              Comment


              • #8
                Current density would normally be around 0.4 A/sq in.

                Ed
                For just a little more, you can do it yourself!

                Comment


                • #9
                  Is this the same process as those "wands" that have some black brush that is electrified and you run it along a weld joint to remove any discoloration? (run on sentence much lol) JR

                  Comment


                  • #10
                    yes, "black brush" is a carbon brush.

                    gary, try 1 amp. as soon as you see small bubles on kathode you have enough current. besides i suspect you forgot do add watter to the electrolyte (should be about 75%). also try nitric instead of sulphuric. what you did is erode the surface. stainless is easy to polish, right after copper. dont try aluminum, your going to kill yourself.

                    edit: if you can controll the voltage watch the current and when it starts falling you are there.
                    Last edited by dian; 12-24-2020, 03:20 PM.

                    Comment


                    • #11
                      No I wouldn't have gotten the same finish with the flap wheel, it was already better than that, I did some welding on it which is why I was trying it, along with a pile of other parts that I should have tried first as I made those. I thought I could learn a new useful process, I built a 200amp electropolishing power supply for a customer about 40 years ago and they used it successfully but I wasn't involved with the process. I would like to build an EDM!

                      Comment


                      • #12
                        I looked into electropolishing once and stopped once I saw the chemicals that are used to do it. Nasty stuff, you have just a portion of what is normally used.

                        Comment


                        • #13
                          you get decent results with just phosphoric, at least on a small scale. nothing nasty about it.

                          Comment

                          Working...
                          X