Rapid evaluation of electroless nickel plating rate on various catalytic metallic substrates using the coulostatic method with finite pulse width

The coulostatic method using a finite pulse width was applied to measure the instantaneous plating rate i dep of nickel from a sodium citratesodium hypophosphite bath using four metallic substrates with different catalytic activities immersed in a stagnant electroless bath (pH 1 - 5.25, 65 - 90 °C). The electrodes tested were: (i) a preformed electroless Ni-P alloy on copper, (ii) copper (purity, 99.98%), (iii) palladium-activated copper and (iv) platinum (purity, 99.99%). The measured polarization resistance R p showed a reproducible inverse relation with i dep ( i dep = KR −1 p ). The proportionality constant K obtained from weight gain, polarization curves and coulostatic Tafel slope measurements agreed very well with catalytic substrates (i) and (iii). For systems using copper or platinum as substrates with low catalytic activity, i dep values resulting from the coulostatic method notably differ from those from polarization curves.