Corrosion of Ga-doped Sn-0.7Cu Solder in Simulated Marine Atmosphere

The surface corrosion behaviors of Sn and Sn-0.7Cu solder in simulated marine atmosphere have been studied. The results showed that pitting and uniform corrosion are the two main initial damage types in the corrosion process. During uniform corrosion, the initial corrosion products, which gradually develop a laminated corrosion film with microcracks, are fragile and easily spall off the surface, thus giving little resistance to further corrosion. XRD of the long-term corrosion products showed that they are mainly amorphous SnO and crystalline Sn(OH)₂ and SnO·xH₂O. Doping the Sn-0.7Cu with gallium significantly improved the corrosion resistance of the alloy in the salt spray test. X-ray photoelectron spectroscopy results showed that the trace amount of Ga significantly segregates to the surface of Sn-0.7Cu alloy and forms a composite oxide layer after solidification in air, thus improving the corrosion resistance. On the other hand, doping the Sn-0.7Cu alloy with phosphorus had little effect.