Mechanistic studies of electrodeposition for bioceramic coatings of calcium phosphates by an in situ pH-microsensor technique

A pH-microsensor technique was developed to measure in-situ the pH value at the titanium alloy \ solution interface for the first time during the electrodeposition process of calcium phosphate coatings. Electrochemically prepared iridium oxide was used as a pH sensitive material, which is of a good response behavior in the measured solutions. The pH response slope was - 70.2 mV/pH at 60 degrees C. The results indicated that the interfacial pH increased with the applied current density, first jumped to a maximum, then slowly decreased at the controlled current density during the electrodeposition process. Incorporating the results of composition and structure of electrodeposition coatings characterized by X-ray diffraction (XRD) patterns and Raman spectra, the measurement of the interfacial pH was informative for further understanding of the electrodeposition mechanism of calcium phosphates. The interfacial pH may determine the precipitation reaction and the electrodeposition products at the titanium surface. (C) 1998 Elsevier Science S.A. All rights reserved.