Electrochemical behaviour of lead-free Sn–0.7Cu–xIn solders alloys in 3.5 wt% NaCl solution

Various electronic equipment has been exposed to a very harsh atmospheric condition that results in corrosion of the solders inside it. The type of corrosion, in most cases, is electrochemical. The lead-free solders are mostly preferred as the solder. Electrochemical corrosion behaviour of lead-free solder Sn–0.7Cu alloys with a variation of indium of x = 0–3 wt% was studied in an air-saturated aqueous solution 3.5 wt% NaCl at room temperature. The potentiodynamic polarization test shows that corrosion resistance improves with In content. The addition of indium refines the microstructure and improve Sn–0.7Cu solder alloys’ corrosion resistance by lowering the current density (I_corr), resulting in high resistance of the passive layer formed. XRD analysis shows that the composition of corrosion products also changed with indium content variation, phases such as Sn₃O(OH)₂Cl₂, and oxides and chlorides of Sn were formed. Electrochemical impedance spectroscopy analysis shows that Indium addition changes the behaviour of the electrochemical interface from charge transfer to diffusion control.