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Analytical Control of Typical Nickel / Chrome Plating Processes

2004

Our company is in the process of a new 'continuous improvement' process. We are also working in our Coating Laboratory.

We feel we have a good system in place but it was asked of us if we have too tight or too loose of ranges.

I am curious as to what ranges others run for some of their plating processes. Most suppliers give a pretty wide range and say "it's what works best for you". I am not looking for a concentration but how tight you should hold your range in oz/gal, pH, percentage, etc.:

• Decorative hex chrome: Chromic acid range - sulphate - ratio - active fluoride - Temperature (I am most interested in this info right now).
• Semi-bright nickel(Watts bath): Ni Metal - Ni sulphate - Ni Chloride -boric acid - pH - Temperature
• Bright Nickel - Ni Metal - Ni sulphate - Ni Chloride - boric acid - pH - Temperature
• Soak Cleaners/Electrocleaners - Concentration in oz/gal or percent - Temperature - pH
• Acid Salts / Activators - Concentrations in oz/gal or percent - Temperature (if heated)- pH

A question for companies that are ISO Certified as we are... if you have a pH in the nickel with a range of 3.8-4.4, yet, occasionally someone adds just a bit too much acid and the pH hits 3.6 and you know you still produce acceptable parts.....how do most handle this? would you add carbonate to raise the pH so your compliant or would you change your range down to 3.6?

Gloria Schwedler
captive plating shop - Indianapolis, Indiana, USA

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2004

Gloria,

You will do well to start with 10 percent plus minus of the spec your Proprietary supplier gives you for starters. Next will be to actually follow the " what's best " approach, because no two plating machines and components in bath are the same. The same width of parameters have to be built into your Standardisation specs , eventually.

Example:

A component needs a low thickness bright finish on a Duplex Nickel Line. Your bright bath is spec'ed at pH 4.2.by supplier.

You probably put in just the right thickness of SB Nickel, the regular lo to semi Bright type, you will run Bright Nickel pH around 4.8 to 5.0 or so to get it bright quicker. Of course I presume you use a contemporary Bright Process.

There are a lot of similar situations where Supplier specs remain for start up and users evolve their own " Best Fits " as they go along.

Thats how most platers function. I am a supplier, and I do see a lot of new standards evolving after the baths are set up.. Good Luck.

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016

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First of two simultaneous responses --2004

A pretty big question, one of the best investments I have ever made is buying "Introduction to statistical quality control" by Douglas C Montgomery and a software Statistical analysis package, there are a few about, most you can download demonstration packs before you decide to buy. I guess the answer what works for you sounds a bit flippant from the supply houses but thats generally the case. I personally don't think that if you specify your pH range to be say 3.8 to 4.2, and you occasionally get 3.6 due to overzealous additions is a major problem, if your product meets all your customers requirements, (could you demonstrate what if any difference it would make to the deposit properties ?, internal stress for instance, and would this difference be significant, again a stats package running tests of statistical significance helps in putting numbers on things to demonstrate to your auditor why you've specified your process control figures)it might just be a case of say specifying in your process control documentation a preferred range and a max and min limit were you can still produce product but perhaps with tightened inspection if you find the need for it between the preferred range and either the max or min limit.

Sorry to be general, but most of us have to crunch our own numbers for our specific plants.

Regards,

Richard Guise
- Lowestoft, U.K.

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Second of two simultaneous responses --

Hi Gloria,

ISO will want you to document your process qualification process apart from your suppliers recommendations. So if 3.6 works fine for you, you are free to incorporate it, but bear in mind that using such low pH will dissolve iron much faster in your baths in the long run.

I would not add anything apart from good old DM water in my tank to ever raise PH.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2004

Industry Standards are not divine law. As with other departments of life, they can be negotiable within reasonable limits, but once established they have to be followed. If a standard is particularly tight or does not give a specific answer, then a particular question might be posted here and someone might give you a goodwill opinion, but you seem to be questioning almost every process in your plant.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

For a pH I've seen over adds bring the pH down to as low as 2.6 and the bath works fine. That is for bright nickel. Semi bright nickel is a little more touchy when it comes to pH.

Jason Deible
Plating - Grand Rapids, Michigan, USA
2004