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Zinc plated part turning dark after blue chromate

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  • Zinc plated part turning dark after blue chromate

    I got my Caswell zinc plating kit 6 months ago and have had nothing but success! The parts look great. I have not plated anything in around a month or so. Now the parts come out looking great but when I dip them in the blue chromate for 15 seconds they are turning dark. Any ideas on what this could be? I wonder if some of the distilled water in the blue chromate has evaporated since it is hot and in the garage. Maybe it is too dense and water needs to be added? Thanks for your help.

  • #2
    Greetings gplracer, I have never experienced this type of response. Could you explain "turning dark"? Is it turning black or gray? Is the part still shiny? Are you pre-dipping in nitric or other acid solution?
    Thank you


    • #3
      Thanks for responding to my question. You know how the parts have an irridescence or rainbow look ot them after they have blue chromate applied to them? It is like that but much more intensified. I see yellow and purple. I only put it in the blue chromate for 15 seconds. If my caswell plating solution needs to be cleaned is there a way to do that without replacing it. I do not know if that is the issue. I am just guessing. Thanks for your time.


      • #4
        Greetings gplracer. With respect to cleaning the plating solution: I have the 1.5 gallon kit. After a daily session of about 15 strings at 1/2 hour each I strain my solution through a paper coffee filter. I drilled about 20 1/4 inch holes in the bottom of a clean yogurt container and a paper coffee filter fits nicely. This takes away all the sediment. I then store the solution in 1 gallon DI water containers. Upon reuse I strain the bottom 3 inches of the solution. Not sure if this is proper but it keeps the solution clean. Good luck. KRR