Anodic Dissolution of Pure Aluminum during Electrocoagulation Process: Influence of Supporting Electrolyte, Initial pH, and Current Density

In this work, effects of some experimental parameters (supporting electrolyte, initial pH, and current density) on aluminum corrosion and anodic dissolution of aluminum during electrocoagulation process were investigated. Potentiodynamic polarization tests, impedance spectroscopy measurements and potentisotatic current density transients were used to evaluate corrosion parameters and verify effects of supporting electrolyte and initial pH on aluminum corrosion. The presence of NaCl and Na2SO4 shifted the corrosion potential toward more cathodic potentials, indicating that corrosion of aluminum is catalyzed by the presence NaCl and Na2SO4. On the contrary, the presence of NaH2PO4 increased the corrosion potential, which indicates that the presence of NaH2PO4 inhibits the corrosion of aluminum. Galvanostatic electrolyses demonstrated that measured concentrations of aluminum exceeded theoretical values calculated using Faraday's Law. The excess in dissolved aluminum produced during galvanostatic electrolyses is primary due to the chemical dissolution of aluminum, which is more significant at highly alkaline conditions. A final pH of value around pH 9 was observed in the presence of NaCl for pH values in the range pH 4-11 which can be explained by buffering effects of aluminum hydroxides.