Plating Q&A: Sulfamate Nickel Problem
Why is there an increase in chloride?
Q. We use sulfamate nickel plating baths. Testing bath composition shows an increase in chloride content from week to week. What causes the increase in chloride content? Also, what happens if the chloride concentration becomes high?
A. When a sulfamate nickel plating bath is formulated with chloride ions, nickel chloride is usually used as the source of the ion to aid in the dissolution of the anode. In many cases the bath is used without the presence of chloride ion.
The simplest way to reduce chloride ion concentration is to dilute the bath and bring other components up to the required concentration. What causes the chloride ion concentration to increase? There are a number of potential culprits:
- An operator made incorrect additions of nickel chloride to the plating bath
- The makeup water you are using contains chloride ion
- The use of HCl to control pH
- Drag-in from a prior process tank
I suggest you investigate each of these possible causes with particular attention to the quality of your makeup water and drag-in from a prior processing tank. Chloride ion increases the stress in your nickel deposit. Excessive stress can cause cracking and peeling of the deposit.
Originally published in the November 2015 issue.
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