Number 1: Before you put the bath in, passivate the tank and all the plumbing. Passivation is when you’re dissolving the nickel with a nitric acid, using a stainless tank in which you’re putting a passive film which stops it from plating out. A good nitric will stop it from plating out immediately. I’ve seen it happen many times. I’ll get the call and say, “Hey, I put a brand-new bath in and it’s plating out immediately.” Make sure the nitric is good.
Number 2: Control. You need to control the parameters: nickel, hypo, pH, and temperature. If you are charting it and don’t have control, you’ll have a saw effect with the bath going all over the place, causing plate out. So, control is number one.
Number 3: Rinsing. Good rinsing is crucial before the bath itself, typically, you want to use DI water or RO water if you have access to it. The cleaner the rinses are, the less contamination you’re going to bring into your bath.
Number 4: Filtration. Good filtration means filtering 10 to 20 times an hour, otherwise you’re not really filtering that bath. Bag filters and the easiest to change and allow you to see what you’re catching but keep them out of the tank as they take up real estate and are creating an active spot. Anything can plate an EN bath if it has an active spot, if that bag touches the steel or nickel, it will start plating out.
Number 5: Idle time. This is something we see a lot. Example: You start up a bath, it’s at 190 degrees, six grams per liter of nickel, 30 grams per liter of hypo. The hypo starts to break down, you build ortho and then the stabilizers break down a little bit creating an imbalance. To fix the ratio, you make your additions one-to-one, add a gallon of nickel, add a gallon of a hypo, and as you go through the bath life, your hypo could drop, and your one-to-one ratio is no longer there. Check your hypo as a separate test, or you could run that ratio off too long and end up with premature plate out or other issues.
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