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  • Bronze turning brown in degreaser

    I'm cleaning gunmetal bronze after polishing by washing with lacquer thinner then followed up by washing with dish washing detergent but it still didn't pass the waterbreak test. Into the heated SP degreaser wheras my part turned a multicoloured brown, almost like it was overheated or it hyper-oxidized. It seems to pass the waterbreak test but I'm reluctant to plate. It really takes a bit of effort on the buffing wheel to cut through the brown. I'm planning to apply electroless nickel. The piece is a steam cylinder cover with many holes both through and blind for the buffing compound to hide in but I was pretty tenacious with making sure most of it was washed away with the Lacquer thinner. I also have the Maskit applied to these parts. Should the maskit be applied after degreasing? Masking the pieces does take some time as they are intricate and I'm afraid by the time I finished the polished metal will have oxidized. Perhaps I need a different degreaser?

  • #2
    Re: Bronze turning brown in degreaser

    It's most likely oxidation, the SP degreaser can do that with some metals. You can use a acid pickel to clean up the oxidation, but it's good you questioned it, as the EN would come right of an oxidized surface. You'd be better off doing an electroclean, but if you plan on using maskit, most of the time it'll cause it to get ''scrubbed'' off by all the bubbles while electrocleaning. You should be using the degreaser for bronze at around 140, if you go much higher, it'll oxidize that much quicker, but you really should be using a pickel to get the best adhesion from the nickel. BUT! you've got to be really careful on which pickel you use, as it'll attack particular metals in the alloy at different rates, which can etch it unevenly or pit the metal.
    Get a nylon bristle brush or a grout sponge and scrub the heck out of the piece while it's in the degreaser, that'll get things moving much faster, and slow down the oxidation. Call Caswell and ask them how bronze reacts in pickel #4, I'd check for you but don't have any bronze on hand. Most often times you need a mixed acid pickel at very precise proportions to avoid the uneven etching or pitting that I described. Let me know, I can do some research for you if you'd like.

    Ohh, and do yourself a favor and post your plating questions directly under the electroplating section, your chances of getting a response are much higher!

    Originally posted by steamachine View Post
    I'm cleaning gunmetal bronze after polishing by washing with lacquer thinner then followed up by washing with dish washing detergent but it still didn't pass the waterbreak test. Into the heated SP degreaser wheras my part turned a multicoloured brown, almost like it was overheated or it hyper-oxidized. It seems to pass the waterbreak test but I'm reluctant to plate. It really takes a bit of effort on the buffing wheel to cut through the brown. I'm planning to apply electroless nickel. The piece is a steam cylinder cover with many holes both through and blind for the buffing compound to hide in but I was pretty tenacious with making sure most of it was washed away with the Lacquer thinner. I also have the Maskit applied to these parts. Should the maskit be applied after degreasing? Masking the pieces does take some time as they are intricate and I'm afraid by the time I finished the polished metal will have oxidized. Perhaps I need a different degreaser?
    James Bateman

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    • #3
      Re: Bronze turning brown in degreaser

      Thanks James, I thought that related to degreasing, it should be posted here but I guess it's the whole process I'm attempting that needs to be considered. This endeaver has proven to be more complicated and frustrating then I had anticipated...I will check with Caswell as to using pickle # 4 with bronze...

      steamachine

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      • #4
        Re: Bronze turning brown in degreaser

        I understand the frustration, I've certainly been there, don't be afraid to ask for help, at any step in the process. Also, be sure to practice on other pieces first until you become comfortable. There's many accomplished plater's here. There's even a few guys that specialize in handguns, we'll get you through it. I checked the spec's on Pickel 4, and it lists copper and brass, but doesn't mention bronze. You'll find that scrubbing the piece in the pickel with a grout sponge will help when you get to that point. Also, get a good rinse set up going, rinsing is a VERY important step.

        -Jimmy.
        Originally posted by steamachine View Post
        Thanks James, I thought that related to degreasing, it should be posted here but I guess it's the whole process I'm attempting that needs to be considered. This endeaver has proven to be more complicated and frustrating then I had anticipated...I will check with Caswell as to using pickle # 4 with bronze...

        steamachine
        James Bateman

        Comment


        • #5
          Re: Bronze turning brown in degreaser

          I have some jewelers pickle here, Sparex#2 Sodium bisulfate which removed the oxidation upon immersion. Whether it would be enough to etch the surface for plating, I'm not sure. I also have some Iron pieces that are going to be nickel plated. Would they need to be pickled as well? The pickle I have is only good for non-ferrous and will copper plate ferrous. It seems as if all of these processes need to happen one after the other Buff, clean, rinse, degrease, rinse, pickle, rinse, plate, rinse. I've found I need to store the buffed and cleaned pieces fully submerged in distilled water to prevent oxidizing, although the iron and steel pieces do alright exposed.

          Steamachine

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          • #6
            Re: Bronze turning brown in degreaser

            If it removes the oxidation, you're good to go, pickel it for a minute or so, rinse then plate. You'd know if its etching it too much as it'd bubble a lot. You're absolutely correct on the process order. Don't let the piece dry out after you pickel, keep it wet while you're going into your plating bath. You may have trouble with the iron, depending on which alloys are present. EN won't plate onto lead, and needs a strike first. Sometimes you'll find lead in cast iron. Steel can be the same way, but most of the time you're fine. A good pickel for steel is 10% sulfuric acid (diluted battery acid), or Caswell's pickel #4.

            Originally posted by steamachine View Post
            I have some jewelers pickle here, Sparex#2 Sodium bisulfate which removed the oxidation upon immersion. Whether it would be enough to etch the surface for plating, I'm not sure. I also have some Iron pieces that are going to be nickel plated. Would they need to be pickled as well? The pickle I have is only good for non-ferrous and will copper plate ferrous. It seems as if all of these processes need to happen one after the other Buff, clean, rinse, degrease, rinse, pickle, rinse, plate, rinse. I've found I need to store the buffed and cleaned pieces fully submerged in distilled water to prevent oxidizing, although the iron and steel pieces do alright exposed.

            Steamachine
            James Bateman

            Comment


            • #7
              Re: Bronze turning brown in degreaser

              I was wondering about letting the piece dry out, thanks!

              As for the lead, I looked up the alloy I used for most of the iron parts I machined and there is no lead in it. One part is an unknown, How would I know, would it just not plate? I'm curious when something doesn't plate does it still count against my credit? And what is "a strike"?

              Thanks again for your help. I think I was closer to solving some of these issues than I thought I was yesterday.
              Last edited by steamachine; 08-05-2009, 10:55 AM.

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              • #8
                Re: Bronze turning brown in degreaser

                The EN will plate around the lead on a microscopic level, and eventually leads to rust spots. A strike is a layer of plate that would be more compatible with the base metal. For example Caswell's flash copper will plate onto just about anything, so you'd apply a very thin (strike) plate of flash copper, then proceed to the EN, as the EN will plate direct onto copper.
                You'd have to check with Caswell as far as the credit term, not sure there. I've never done EN nickel, just normal Electrolytic nickel.

                Originally posted by steamachine View Post
                I was wondering about letting the piece dry out, thanks!

                As for the lead, I looked up the alloy I used for most of the iron parts I machined and there is no lead in it. One part is an unknown, How would I know, would it just not plate? I'm curious when something doesn't plate does it still count against my credit? And what is "a strike"?

                Thanks again for your help. I think I was closer to solving some of these issues than I thought I was yesterday.
                James Bateman

                Comment

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