Electrochemical characterization and immersion corrosion of a consolidatedsilver dental biomaterial

A consolidated silver (CS) material, an alternative to dental amalgam, was studied for corrosion. Chemically precipitated silver particles were acid a ctivated and pressure consolidated to a volume porosity of 25%. In selected tests comparisons were made between CS and melted and cast silver particle s (MS), silver with a known mass fraction purity of 99.998% (FS), a silver- palladium alloy (SP), and a dispersed-phase amalgam (DA). Fusayama artifici al saliva was used with controlled variations in pH, sulfide content, mucin content, and absorbed oxygen content. Electrochemical polarization, electr ochemical impedance spectroscopy, and immersion methods were used. Results revealed differences in the zero current potentials E(I = 0) from forward p olarization between CS and MS (or FS) in deaerated solution, By superpositi on of the cathodic polarization curves, the area for CS was increased by 7. 3 times and was enclosed within an outer shell of material 5.5 mum thick. P olarization resistance was significantly the highest for SP, followed in or der by MS (or FS) and CS or DA. With scanning electron microscopy, CS was s hown to be significantly more susceptible than MS to long-term immersion co rrosion. The modeled equivalent electrical circuits for CS and DA involved a double layer capacitance, a charge transfer resistance, and an element at tributed to adsorption. The active pore depth for CS from the transmission line model for porous solids revealed satisfactory agreement with polarizat ion results. It is concluded that the corrosion susceptibility of CS in Fus ayama solution, while similar to that for DA, is greater than it is for MS. (C) 2001 Elsevier Science Ltd. All rights reserved.