Study on the effect of ultrasonic waves on the characteristics of electroless nickel deposits from an acid bath

The effect of ultrasonic waves on the properties of electroless nickel deposits was studied using an acidic bath of different pH values ranging from 4.3 to 5.7. Three frequencies, 28, 40 and 68 kHz, were applied to the bath containing different amounts of Pb(NO3)2 as a stabilizer up to 2.8 ppm. The deposition parameters were optimized in view of the hardness, surface morphology and the deposition amount by employing a statistical technique of central composite design (CCD). Thus, the deposition amount was improved by 15% and the hardness increased by 11%. The maximum deposit amount and Knoop hardness were obtainable in this study as a result of the application of an ultrasonic wave frequency at 40 kHz to the bath with a Pb(NO3)2 content of 0.4 ppm at pH 5.5. Although the ultrasonic frequency increased, pitting and erosion phenomena did not appear on the plated surface.