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Copy Chrome Over Plastic

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  • Copy Chrome Over Plastic

    Good morning everyone,

    Hope all of you are staying sane during this crazy time.

    I need some help. I am trying to plate some plastic parts, different shapes and sizes. The largest part is approximately 3 inches across and has a surface area of about 11 inches square. I am using the 2 gallon Copy Chrome Kit. The copper tank is agitated using the filter provided. I am using copper wire to hang the part in the process. The larger parts are being hung through bosses in the plastic in 2 locations. The process I am following goes:

    1. Degrease
    2. Rinse and dry part
    3. Spray paint plastic with conductive paint
    4. I have tried cleaning and not cleaning at this point, doesn't seem to matter.
    5. Bright copper plate
    6. Polish

    This is where I get to because after this I am having problems polishing the copper. There are couple of reasons it seems.

    1. The plating on the larger parts are blistering in the high current density areas. I was plating the larger parts at 2V and .07 amps per square inch originally, but I lowered it to .02 amps per square inch. This seems to have solved the blistering issue on the larger and smaller parts, to do this I turned the voltage down to 1V or less. Takes longer to plate but it is giving me a more consistent plate.

    2. The plating on the edges and corners is very thin and when I polish the part it polishes the edges off. I need the copper polished because when I put the copper in the nickel the plate isn't smooth and the nickel exaggerates the unsmooth finish and while the nickel comes out shiny as expected the plating is rough.

    3. I have tried polishing using a buffing wheel with compound and it is too rough. I tried using multiple compounds, gray, red, brown, and blue but nothing seems to be working the way I expect. I have also tried using a vibratory bowl but it doesn't polish well and when it does it again ends up removing plating from the corners.

    Does any one have any suggestions to polish the copper so that it doesn't come off the part? I also tried plating thicker, but like I expected that led to blistering again in the high current density areas.

    Just for some background, I have significant experience barrel plating zinc and zinc-nickel on mass production lines, but I have never plated copper, nickel, or chrome, minus using a chromates as a topcoat over zinc and zinc-nickel. I have never rack plated before and this is definitely more a rack plating process.

    Also some more information about the process

    1. Base metal of your part - Plastics of varying types

    2. Surface area of your part - 2.5 to 11 sq. inches.

    3. Which plating kit you are using - Copy chrome kit over nickel conductive spray paint

    4. Amperage used - Started at .07 amps per square inch and have plated as low as .02 amps per square inch

    5. Voltage used - .75V to 2V

    6. Temperature of your plating bath - Controlled at 110 F.

    7. Duration of plating - Varies on part, but at low amperage/voltage as short as 15 minutes to as long as 40 minutes

    8. What you are using as a power supply (ie. car battery, charger, rectifier) and the supply's specifications.- 5 AMP rectifier I purchased from Caswell

    9. What your surface prep was (and remember...90% of all failed jobs can be traced back to bad prep) - Degrease before and after spray paint. I also tried not cleaning before spray paint and after spray paint

    I'm really looking for suggestions for polishing the copper. If I can get this done, I am fairly confident that the rest of the process will go smoothly. I know this because I have plated the other processes over the copper and if the surface was polished properly the parts would look perfect as the nickel comes out shiny after plating, just not smooth.

    Thanks for all your help in advance. If you need any more information let me know.