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Dark streaks in CopyChrome 7 Adjusting PH

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  • Dark streaks in CopyChrome 7 Adjusting PH

    Hi,

    The first few parts I plated came out good. Then I tried to plat a part that I think had zinc on it. Now everthing is part shiney and part dull. I read about "plating out" the zinc, and tried for hours, but it is still the same. I checked the ph and it is a bit high (around 5-6). The manual says to adjust it. So, my questions are:

    1. If I can't plate out the zinc, maybe it is some other problem. Any thoughts?

    2. Is it ok to use pool chemicals to raise/lower the ph?? I couldn't find anything in the manual about what to use.

    Thanks for your help!!

    M

  • #2
    This is likely a problem for the Tech Support group, but here is a thought or two.

    Sometimes you can improve the performance of the nickel/copychrome bath with an adjustment of the brightener levels. I believe the nickel/copychrome brightener specifies 2 oz/gallon for replenishing. Certain kinds of contamination in the bath can sometimes be "buffered out" with the brightener, but not always. It's worth a try and it shouldn't hurt it as long as you don't overdo it.

    I'm assuming you already tried to filter the solution with carbon filters. This won't get the zinc out. Plating a dummy should have accomplished that. But if you've tried an hour at high currents (perhaps 500mA/sq in) with a dummy and that didn't help, then perhaps there is organic drag in from cleaner, etc. and filtering and recharging with brightener is worth a try.

    The fact that the pH is up where it is makes me wonder if you've contaminated the bath with drag in from the cleaning solution which has a higher pH. Do you rinse thoroughly after cleaning and before the plating step? Try using 2 rinse baths ahead of the plating tank.

    I use muriatic acid from Home Depot to adjust the pH. It must be added carefully, a teaspoon per gallon at a time, allow 1 hour to settle with aeration, then measure the pH. It will change rapidly so be very careful not to overdo it, or you'll be in trouble from the other side. It's also worth noting that it's possible to get good results from the nickel tank even when the pH drifts up to around 5. Not sure how this applies to copychrome.

    Ken

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    • #3
      Re: Dark streaks in CopyChrome 7 Adjusting PH

      I am haveing the same problem with dark deposits or streaks on the part. The rest of the part is shiny and looks good, its just that there are dark spots on them here and there. They can be buffed off very easy but I don't want to buff I want the part to come out perfect. havent tried using a dummy and the PH seems to be perfect.

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      • #4
        Re: Dark streaks in CopyChrome 7 Adjusting PH

        I've found that dark deposits come from dragged in copper although I'm sure there could be other reasons. It should plate out using low current density dummying 2-5 A/sq ft. for a few hours.

        Ph ought to be adjusted using sulfuric acid I think since adding HCl will change the nickel chloride ratio which has a greater impact on plating properities than sulfate. Also, HCl is volatile and you can lose some via evaporation whereas sulfuric acid isn't. I've used that Home Depot HCl also and I think it has a significant amount of iron among other things in it. Not very pure. Sulfuric acid that you get from auto parts stores is much better since it's meant for batteries.

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        • #5
          Re: Dark streaks in CopyChrome 7 Adjusting PH

          PH can be raised simply by agitation. As far as the dark spots it is possible that you are using to much current or even to close to the anodes when plating of course be sure that you parts are rinsed and free from any copper solution before putting them into the copy chrome
          also this formula has worked for me I plate at between 95 and 110 degrees using 1 amp per 32 sq inches instead of 1 amp per 16 sq inches this has been working for me with the copy chrome
          Jim Eaton

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          • #6
            Re: Dark streaks in CopyChrome 7 Adjusting PH

            My suggestion is to use HCl for pH adjusting based on several factors:

            1. Many articles read on the composition and maintenance of nickel and cobalt baths will suggest HCl. The Caswell support team suggests HCl as well.

            2. Using HCl I have maintained the same baths now for almost 3 years with excellent results, every time, no buffing needed afterwards. I agree that avoiding buffing after nickel or copychrome is a very good practice.

            3. Going against Caswell's recommendation, I ruined my previous batch of nickel by adding sulfuric acid to it in an attempt to get the pH right.

            It's true that some aspects of plating are as much finesse as science. What works for some doesn't work for all because there are often conditions that are being used that don't get described along with the problem.

            To avoid any concerns about Home Depot HCl, a small bottle of laboratory grade HCl can be obtained at reasonable cost from numerous chemical suppliers, like Daigger. You can order it on line if you want, too.

            Be sure that you have sufficient agitation. An open tube at the bottom of the tank will provide the large sized bubbles you need to substantially agitate the solution. If your tanks are large, you might want to consider several tubes with multiple pumps. Also, a small addition of brightener might help eliminate dark spots.

            Ken

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            • #7
              Re: Dark streaks in CopyChrome 7 Adjusting PH

              Originally posted by dadkar2
              2. Using HCl I have maintained the same baths now for almost 3 years with excellent results, every time, no buffing needed afterwards. I agree that avoiding buffing after nickel or copychrome is a very good practice.

              3. Going against Caswell's recommendation, I ruined my previous batch of nickel by adding sulfuric acid to it in an attempt to get the pH right.
              I guess #2 is all that matters, although I don't get how sulfuric acid could ruin a bath. It is used for ph adjustment as well as HCl. I thought this article might be useful for someone as it talks a little about dummying and the effects of metallic contaminants in nickel plating.

              http://www.pfonline.com/articles/pfd0015.html

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