Microstructural array and solute content affecting electrochemical behavior of Sn Ag and Sn Bi alloys compared with a traditional Sn Pb alloy

The aim of this investigation is focused on the electrochemical impedance behavior of Sn-2 wt.% Ag (SA), Sn-10 wt.% Bi (SB) and Sn-22 wt.% Pb (SP) casting alloys in a stagnant and naturally aerated 0.15 M NaCl solution at environmental temperature. Both uncoated and coated samples are casting centrifuged and similar microstructural arrays are produced. Coated substrates and joints utilize Sn-based alloys in microelectronic applications. Gold-coated samples are commonly used in jewelry industry. The roles of the solute contents on the microstructural parameters, eutectic fractions and cathode-to-anode area ratios of each proposed alloy are discussed. Electrochemical impedance spectroscopy (EIS) analysis using equivalent circuit is discussed. It is found that indistinctively of the examined uncoated or coated samples, the corrosion resistance sequence favors the SB alloy, followed by SA and SP alloys.