Investigation of Corrosion Properties of Lead-Free Solder Alloys in 3.5% NaCl Solution

Abstract

The restriction of lead-based solders due to environmental and health concerns has made the use of lead-free alloys essential in the electronics industry. Among the available alternatives, tin-based systems containing silver and copper have been extensively studied for their potential to provide reliable and sustainable soldering solutions. This study investigates the corrosion behavior of Sn–Ag, Sn–Cu, and Sn–Cu–Ag solder alloys in a 3.5% NaCl solution, simulating chloride-induced conditions commonly encountered by electronic components in humid or coastal environments. The samples were subjected to potentiodynamic polarization tests using a three-electrode system consisting of a saturated calomel electrode (SCE) as reference, a platinum counter electrode, and the solder alloy as the working electrode. The electrochemical results revealed clear distinctions among the tested alloys. The Sn–Cu–Ag alloy exhibited the lowest corrosion current density (4.3×10-6 A/cm²) and the most positive corrosion potential (–0.733 V vs. SCE), better corrosion resistance compared to binary Sn–Ag and Sn–Cu systems. Both Sn–Ag and Sn–Cu alloys also achieved current densities around the 10⁻⁶ A/cm² threshold, which is generally considered acceptable for electronic solder joints, confirming their applicability under mild corrosive conditions. Overall, the results highlight that the Sn–Cu–Ag system offers the most balanced performance and electrochemical durability. The findings contribute to the optimization of lead-free solder materials and support their integration into reliable, long-life electronic assemblies.