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Masking areas not to be plated

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  • Masking areas not to be plated

    Hi All,

    I have a small electrical relay that I want to plate using my 1.5 gal. Copy cad/zinc kit. I only want to plate the metal cover and bracket but do not wish to disassemble the relay. My question is, what can I use to seal the bottom of the relay. It looks to me as though I could paint the bottom and all connections with something like the urethane paint you use on furniture or perhaps model airplane dope that's hot fuel resistant. Is there any reason why this would not work?

    Thanks, Art.

  • #2
    Re: Masking areas not to be plated


    Powdercoat masking tape works good on smooth flat surfaces. These shafts were masked that way (photo links to larger image):

    and Caswells "Mask-It" works good on irregular surfaces. Don't have any photos of that though.

    Beware, if ANY electrolyte seeps through into the relay, it will corrode badly, unless you can rinse it out 100%.

    Seans Zinc Plating page


    • #3
      Re: Masking areas not to be plated

      Hi Sean,

      Thanks for the reply. Obviously, if I get a leak, the relay is junk. I have several to re plate if this can be made to work. All of them work just fine, they just aren't pretty, hence the desire to re plate them. The other option is to buy all new ones, but that seems a wast. The base/bottom is some kind of fiber board stuff as you usually find on a relay but I think the two things that I mentioned would adhere OK. I didn't intend to fully submerse the relay, just was going to try to insert the relay upside down, to the edge, of course knowing that I would get some slosh over onto the fiber board.

      The mask-it that Caswell sells would probably work but I would have to order it, pay shipping, and wait. I was hoping that something else that is more readily available would work as well.



      • #4
        Re: Masking areas not to be plated

        Art, try using "Best-Test" brand white rubber cement.
        It is available at most art/office supply stores.
        You may also want to pick up a small can of rubber cement thinner to thin the cement to make it easier to apply (and of couse a small paint brush if you don't have one).
        The thinner in the rubber cement (naptha) will have no effect on the coil insulation.

        Apply with small brush (about (3) coats).
        Let dry at least 1/2 hour.
        Be careful handling the part while hooking up to the lead wire (the rubber cement peels off pretty easy)

        After plating the rubber cement can be peeled/rubbed off real easy.

        You could always coat the part with a few layers of clear lacquer and it would seal up the areas without having to remove it after plating.
        The solvents in the lacquer "may" attack the insulation within the relay's coil if you thin the clear lacquer out too much.

        Be careful if you use clear model airplane "dope" as the thinners may also attack the wires insulation within the coil.

        BTW, I have attached photo of a penny that I plated using the white rubber cement to mask off everything except Lincoln's bust so you can see it works and how precise you can get using this masking media.

        George W.
        Orlando, FL
        Attached Files


        • #5
          Re: Masking areas not to be plated

          Hi Art:

          As George has said, there are off-the-shelf products that work. I've never used them myself, since I had the Mask-It and powdercoat tape since day one.

          There's been other posts here about masking, if you search for "mask" or "masking" you'll find what works.

          Aside from rubber cement, I do know that silicone seal works well, but it's near impossible to remove afterwards. That's what I like about Mask-It, it peels off cleanly. I don't know what's in it, but it's similar to rubber cement, a bit thicker and green in color.

          Good luck! Take pictures & let us know how it all turns out.

          Seans Zinc Plating page


          • #6
            Re: Masking areas not to be plated

            Is there any way to separate the lids from the relay? It only takes the smallest trace of plating bath to destroy a relay contact. And, the effect might not be evident right away, but months down the line the contacts will fail.