The Effect of Hydrogen on the Rate of Formation of Intermetallics in the Cu-Sn, Ag-Sn and Ni-Sn Systems

The purpose of this work was to determine if changes in surface free energy via adsorption of hydrogen will alter the rate of formation in the Cu-Sn, Ag-Sn and Ni-Sn systems. Metallic couples, prepared by depositing molten tin on Cu, Ag or Ni, were subjected to temperatures slightly below the eutectic temperatures for time periods up to 40 hours in hydrogen or air. After this treatment the couples were cross sectioned and polished so that the interface could be examined. The rates of compound formation in those couples subjected to hydrogen were found to be drastically reduced. An analysis based on diffusion and surface free energy changes was made to explain these observations. This analysis can be applied where the driving force for diffusion is approximately equal to the decrease in surface free energy caused by hydrogen adsorption.