Electrochemistry of electroless plating

The present review describes the electrochemical aspects of electroless plating in four sections: (1) electrochemical polarization behaviour; (2) catalytic aspects of electroless plating; (3) mechanism of anodic oxidation of reductants; (4) methods for determination of the rate of electroless plating. It is stressed that electrochemical polarization studies in an electroless plating bath is a powerful method for assessing the adaptability of the bath and for obtaining mechanistic information, although the anodic and cathodic reactions are more or less interdependent when they occur simultaneously. Catalytic aspects of electroless plating are discussed on the basis of the polarization curves for the anodic oxidation of reductants. The mechanism of anodic oxidation of reductants is discussed on the basis of a computer simulation of the current density-potential curve assuming several reaction schemes. Attention is focused especially on the occurrence of the volcano-shaped polarization curve. It is established that the polarization resistance (the slope of the current-potential curve at the electroless plating potential) is inversely proportional to the rate of electroless plating.