It’s important to check various points on a plating bath on a regular basis in order to control a deposit and prevent high levels of rejection. The main points to check are detailed below.
Monitor pH Closely
By maintaining a pH between 4.5 and 5.0 for a mid-phosphorus plating process, nickel can be prevented from precipitating out of solution. When the pH falls below 4.5, nickel deposition will slow down and may even cease altogether. To check the pH of the plating solution on an hourly basis during production and to take action as required using dilute ammonia or sulfuric acid solutions.
Replenish Chemicals Promptly
Nickel ions and hypophosphite are consumed during the plating process. A bath is therefore replenished on a set turnover interval, usually on a metal turnover (MTO). Replenishment should be in accordance with the supplier’s recommendations and should be checked using titration kits on a regular basis.
Filter Out Particulates
Continue to operate the filtration unit and change the filter bag or replace the filter cartridge on a daily basis where operating at heavy loads to prevent the build up of fine nickel particles which will produce rough, pitted surfaces.
Control Operating Temperature
Bath operating temperature for Electroless Nickel Plating typically is in the range 85-95°C, and care must be taken to ensure that the process temperature does not fluctuate. Use of a calibrated thermostat and check against a calibrated reference thermometer on a weekly basis is recommended.
Know When the Bath Is Spent
Products of bath by-products form after 6 to 10 MTOs, at which time the metal finishing solution’s ability to produce a satisfactory deposit ceases to exist. It can produce excess amounts of sludge, spontaneous decomposition and possibly produce a rough deposit. Such a bath must be disposed of in an environmentally responsible manner. Since the disposal of spent baths is a regulated activity, all metal finishing facilities in the UK have to adhere to surface treatment operations within environmental permit requirements.
More on Electroless Nickel Plating can be found at SWMF.
By following these points and keeping the bath up to the correct standards for a prolonged period of time, you should be able to get good consistent metal and get the best out of your plating bath for its working life.
Leave a Reply