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HELP! Copy cad/ zinc plating with yellow chromate

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  • HELP! Copy cad/ zinc plating with yellow chromate

    Got the 4.5 gallon kit and have been fighting getting the yellow chromate to stick. After wasting 2 full working days with no success I called tech support and there manual is written wrong. You are not suppose to use muriatic acid before the chromate. That was my first problem.
    The guy on the line said to dip them into sulfuric acid before the chromate, this helped a little bit but the yellow is still not sticking still
    Is there something I’m missing or doing wrong. Here’s my steps.

    All parts were sonic cleaned,
    then sand blasted,
    Rinsed free of blasting material
    then sp degreaser 20 mins
    Muriatic acid dipped 2-3 seconds
    Spray test
    Plated 20-30 mins
    Sulfuric acid 10-15 seconds
    Rinse x 2
    Yellow chromate approx 1-3 mins to achieve color air dried for 30 mins and into the oven for 1 hour at 100 degrees

  • #2
    How does the zinc plating look before the dip in sulfuric acid? I've never used a sulfuric acid dip before conversion I always go directly form the plating tank, thoroughly rinse in distilled water and then into the yellow chromate (conversion) for no more than 30 seconds.
    20 to 30 minutes is a somewhat long plate time. Is there a reason you plate that long?
    The parts in the picture don't appear to have much plating on them. How are you hanging them or are you barrel plating?
    What is the substrate you're plating? Steel? Alu?
    Are you using distilled water when rinsing?
    What temperature is your plating tank?
    What temperature is your yellow chromate tank?
    What's the ph of your chromate tank?
    What amperage is your power supply set to... and is it a constant current power supply?
    Have any contaminates been introduced into the tanks?
    Are the plated parts thoroughly dry before going into the oven? Better yet, why are the going into an over?
    You should not handle the converted parts for at least 24 hours (and preferably 48 hours) in order to give the chromate sufficient time to harden. Freshly applied chromate can be rubbed off with your thumb... it needs time to harden.
    Sorry for all the questions but you didn't give much to go on.