The corrosion behavior of Sn-58Bi alloy in DL-malic acid solutions with various concentrations

The corrosion behavior of Sn-58Bi alloy in DL-malic acid solutions with different concentrations has been explored via electrochemistry and physical methods. Results indicate films formed on the surface of Sn-58Bi alloy are p-type semiconductors, consisting of SnO2 and nonstoichiometric SnOx (1 < x < 2). With the increasing of DL-malic acid concentration, the corrosion resistance increases first then decreases, and the maximum appears at 7 wt%, where the thickest film and the minimum proportion of SnOx emerge. The SnOx with massive electron holes as charge carriers makes the film less protective. Both the thickness of the film and the proportion of SnOx are responsible for the corrosion behavior of Sn-58Bi alloy in DL-malic solutions.