IN-SITU CHARACTERIZATION OF LEAD CORROSION LAYERS BY COMBINED VOLTAMMETRY, COULOMETRY, AND ELECTROCHEMICAL QUARTZ-CRYSTAL MICROGRAVIMETRY

Concurrent linear sweep voltammetry, coulometry, and electrochemical q uartz crystal microgravimetry (EQCM) were used, we believe for the fir st time, to study anodic corrosion layers at lead. These corrosion lay ers were first generated on the lead surface at 0.8 V (vs. Ag/AgCl/sat d. KCl reference) either in 4.5M H2SO4 or 0.1M Na2SO4. A subsequent ca thodic voltammetry scan revealed waves due to the reduction of the cor rosion layer. Coulometry and EQCM analyses were then performed within the potential window corresponding to each cathodic wave. From these c harge and mass measurements respectively, an n/DELTAM parameter (n = e lectron stoichiometry, DELTAM = molar mass difference between solid pr oducts and reactants) could be extracted and compared with the value c omputed for a model reaction candidate. We thus show that basic lead s ulfates can be detected in the presence of both PbO and PbSO4. Thus Pb O . PbSO4 is shown to be a corrosion product in 4.5M H2SO4 while 3 PbO . PbSO4 . H2O is generated at the lead surface in 0.1M Na2SO4.