Effect of microstructure features on the corrosion behavior of the Sn‐2.1 wt%Mg solder alloy.

Abstract

The Sn–Mg eutectic alloy is a potential replacement for the traditional Sn-38.1 wt%Pb solder alloy, since lead has been banned because of its risk to human health and the environment. However, studies in the literature related to the Sn-2.1 wt%Mg alloy are restricted to mechanical, electrical and thermal properties. Therefore, this study aims to evaluate the corrosion behavior of this alloy, as a function of the microstructural arrangement obtained from directional solidifcation performed in a transient heat extraction regime. The thermal solidifcation parameters (solidifcation growth rate and cooling rate) were determined along the length of the casting for correlations with microstructural features. The resulting microstructure was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray difraction. Subsequently, the electrochemical impedance spectroscopy, linear polarization, equivalent circuit and evolution of hydrogen release analyzes were performed to evaluate the corrosion behavior of the samples in a 0.5 M NaCl solution at 25 °C. Interphase spacing and Mg2Sn fraction were found to infuence the corrosion behavior, showing higher corrosion resistance for a more refned microstructure.