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Plating Small Pot Metal Parts

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  • Plating Small Pot Metal Parts

    I am a hobbyist restoring 70-year-old small chrome telephone parts. The smallest is 1” x ½” x ¼” and the largest is 1” x 4” x ¼”. While stripping chrome off two of the smallest parts with Muriatic Acid, I discovered the parts were pot metal. One had a good coat of nickel and mostly survived but the other now looks like lava rock. Since the chrome is off these parts, I decided to use them as practice pieces to learn to plate pot metal. My eventual plan is to plate good pieces with copper then nickel but no chrome.

    After reading various threads on this forum, I used B-929 to remove the old nickel then sanded off the copper layer to bare pot metal. I then cleaned them in a heated ultrasonic cleaner with a mild alkaline cleaner then anodic electro cleaned them in 8-grams/liter sodium carbonate at 3.0 vdc for 5 minutes. After rinsing in distilled water, I plated them in alkaline copper starting at 700 mA for 15 seconds then 50 mA for 45 minutes. I then sanded with 1000 grit sandpaper, rinsed in distilled water and plated in alkaline copper for 45 minutes at 50 mA followed by sanding. The results were full coverage with excellent adhesion (tape test showed no delamination).

    I am now going back to bare pot metal and will practice filling pits. I tried to sandblast the parts but blew them away. Would an “air eraser” (looks like a pen or air brush) using 220 grit aluminum oxide work just as well for removing chrome and plating prep on small parts?

    The pits seem small – about 0.010” in diameter. Would a 1/64” drill provide a sufficient hole for filling with solder?

    I plan to use 60/40 rosin core solder. What should be used to clean off the rosin flux after soldering?

    If I understand the sequence correctly after drilling out the pits I should alkaline copper plate for 15 minutes then solder. Is that correct?

    Thank you

  • #2
    Re: Plating Small Pot Metal Parts

    A few updates to the original post:

    1. Changed the anodic electrocleaning to 1.5 vdc for 1 minute. Different pieces of the same part configuration reacted differently - some good and some etched. Lowered voltage and time. Copper plating results the same either way. Will try a future test using only heated alkaline ultrasonic cleaning (no electroclean). Parts are passing water break test after ultrasonic cleaning.

    2. 1/64" hole to drill out pits gave problems trying to solder. Actually everything gave problems soldering. Changed to 3/32" Dremel cutter to give dished out recess.

    3. Soldering was a complete failure. Used 0000 steel wool over part surface but it does not get into holes. Solder forms a ball in the drilled hole and does not flow. Preheated part in oven to 300 degrees F with same results. Thought it might be low heat so kept heating part until part deformed and still no flow. Possible oxide not getting cleaned out of hole so will try to liquid rosin flux. Possibly sandblasting would remove oxide from holes?

    At this time I am stuck on the soldering step.



    • #3
      Re: Plating Small Pot Metal Parts

      Post up some pics. It's hard to envision what's going on as there are sooo many variables as to what could be causing the condition. Improper soldering technique, corrosion still in the pit, the list goes on.

      Try soldering on the areas without a pit. What are you using for solder?
      James Bateman


      • #4
        Re: Plating Small Pot Metal Parts

        Hi there, Been reading this post about the difficulties with pot metal. I am an artist experimenting with electroforming natural elements.
        Being a newbie, I am obligated to ask at least one stupid question, right? Just wondering why pot metal parts can't just be treated
        like any other non metal item and coated with conductive paint such as graphite and then plated. Joyce


        • #5
          Re: Plating Small Pot Metal Parts

          Soldering was a complete failure. Possibly sandblasting would remove oxide from holes. At this time I am stuck on the soldering step.