Mechanistic Studies of Hydrogen Evolution during Electroless Nickel-Phosphorus Deposition

Abstract

In the present talk, mechanistic aspects of the electroless nickel-phosphorus (Ni-P) deposition process using sodium hypophosphite as reducing agent will be discussed. We will focus primarily on the mechanism of hydrogen evolution during electroless Ni-P deposition. The role of pH and reducing agent concentration on the kinetics of hydrogen evolution will be discussed. A combination of volumetric analysis of the hydrogen evolved, titration analysis of the hypophosphite consumed and compositional gas analysis when using D2O and H2O as solvents shows that hydrogen evolution proceeds primarily via hydrolysis of the reducing agent rather than electrolysis of water. Mechanistic aspects of the reductant hydrolysis reaction will be investigated using a rotating disc electrode to unravel the role of surface kinetics and mass transport on the hydrogen generation process. Findings will be incorporated into a simple mathematical process model. Implications of the present study to improved process design for electroless deposition of amorphous alloys will be discussed.