Corrosion resistance and corrosion mechanism of hot-dip plated Pb40Sn60 alloy coatings on copper strips in NaCl solution

Copper wires are often used as circuit materials and are exposed to corrosion from the natural environment and the atmosphere. The hot-dip plating Pb40Sn60 alloy coating was prepared on copper strips to enhance its corrosion resistance. The microstructure and phase structure of hot-dip plating Pb40Sn60 alloy coating on copper strip were characterized. The corrosion resistance and the corrosion mechanism of hot-dip plating Pb40Sn60 alloy coating were studied in NaCl solution. The research results show that the thichness of hot-dip plated Pb40Sn60 alloy coatings on copper strips is about 37.1μm. The microstructure of hot-dip plated Pb40Sn60 alloy coating is composed of the equiaxed primary α(Pb) phase and the granular and lamellar eutectic (α(Pb)+β(Sn)) structure. The relative amount of β(Sn) phase in the coating is more than that of α(Pb) phase. The average grain size of hot-dip plated Pb40Sn60 alloy coating is about 4.17μm. The corrosion resistance of hot-dip plated Pb40Sn60 alloy coating is about 4 times than that of copper strip substrate in 3.5%NaCl solution. With the increase of NaCl solution concentration, the corrosion rate of hot-dip plated Pb40Sn60 alloy coatings increases. The corrosion products of hot-dip plated Pb40Sn60 alloy coating on copper strip in NaCl solution are mainly composed of PbO and SnO 2 . The corrosion resistance of β(Sn) phase is better than that of α(Pb) phase. The β(Sn) phase is corroded to form SnO 2 which is dense, but α(Pb) phase is corroded to form PbO which is loose. The corrosion product PbO is prone to fall off or be dissolved, which results in the formation of holes or hollow morphologies on the corroded surface of the sample. As corrosion further occurs, the falling off or be dissolved degree of corrosion products increases, and the formed holes or hollows interpenetrate, which results the corrosion products of the β(Sn) phase to peel off.