Online evaluation of electroless deposition rate by electrochemical noise method
(Applied Chemistry Department, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran)
Abstract: Continuous noise resistance calculation (CNRC) technique was used for online determination of the electroless nickel deposition rate on zirconium pretreated magnesium alloy. For this purpose, the noise resistance (Rn) variation with time was calculated for the pretreated alloy surface in the electroless plating solution. The CNRC results were described by energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) techniques. Also, potentiodynamic polarization and gravimetric measurements were used for determination of the electroless deposition rate at the same time period and the results were compared with the CNRC results. The Rn variation with plating time shows that the electroless plating consists of different stages with various deposition rates. The results of the CNRC and polarization methods were not in acceptable agreement due to the limitations of the polarization method for online monitoring of the deposition rate. However, the results of the gravimetric measurements were in complete agreement with the CNRC technique and so, the CNRC can be considered as suitable tool for online evaluation of the electroless deposition rate.
Key words: magnesium alloy; electroless plating; deposition rate; electrochemical noise; SEM; EDS