Application of Potentiokinetic Hysteresis Technique to Characterize the Chloride Corrosion of High-Copper Dental Amalgams

The potentiokinetic hysteresis technique was utilized to characterize the electrochemical reactions involved in the corrosion of six silver-tin dental amalgams containing approximately 2.0 to 15.0 weight percent copper in a 1.0 percent sodium chloride (NaCl) solution at 23°C over a potential range of −1200 to 0 mV (saturated calomel electrode). The results indicated that the corrosion of these amalgams is associated with several oxidation-reduction reactions, namely, Sn/Sn (OH)₂, Sn/Sn (OH)₄, SN/SN(OH)Cl, H₂O, Cu/Cu₂O, and Cu/CuCl, which are thermodynamically possible in the range of potentials scanned. The occurrence of these reactions at around their respective thermodynamic potentials was clearly indicated during the reverse scan of the potentiokinetic measurement. From the height of the peak currents associated with these various reactions, it is possible to rank these amalgams from the standpoint of electrochemical activities of copper and tin in each amalgam. These results offer an insight into the mechanism of corrosion of dental amalgams, and at the same time demonstrate the usefulness of the potentiokinetic technique in the evaluation of the corrosion resistance of dental amalgams.