Potential-pH curves for electrodeposited 80% Sn-Cu alloy in aerated buffer solutions of pH values ranging from 0.9 to 11.3 show linearity within the range of pH 4.4 to 11.3. The electrode behavior is governed by the Sn(OH)4/Sn(OH)2 system. For the deaerated buffer solutions, the bheavior of the alloy coincides approximately with that of pure tin. Corrosion potentials in solutions of acetic, citric, and tartaric acids within the concentration range 0.05 to 0.5 M do not vary appreciably with the concentration of these acids. Values of Tafel slopes (bc) for the hydrogen evolution reaction vary from −94 mV up to −117 mV with α values ranging from 0.51 to 0.64, indicating a slow discharge mechanism. Lower values for iQ and bc revealed inhibition by adsorption and/or chelation with the surface. Anodic polarization of the alloy reveals two successive arrest potentials corresponding to the systems: SnO2/SnO or SnO2/Sn(OH)2 and CU2O/CU before O2 evolution takes place.

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© 1976 National Association of Corrosion Engineers
1976
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