Constitution Of Anodizing Current And Effects On The Growth Of Porous Anodic Alumina

Field-assisted dissolution theory was the generally accepted mechanism for pore formation and development in porous anodic aluminum oxide (AAO). However, field-assisted dissolution rate or dissolution current has never been reported. The quantitative relationship between the length of AAO and total anodizing current J(total) is unclear, because the constitution of J(total) is hard to be determined in situ. In order to make clear of the constitution of J(total) and effects on AAO growth, different anodizing processes in two electrolytes (0.3 M and 0.7 M H2C2O4) are explored under constant current rather than constant voltage. Quantitative relationship between AAO lengths (y) and total anodizing currents (x) were investigated. Two fitting equations in 0.3 M and 0.7 M H2C2O4 are y = 0.92(x-4.58) and y = 1.00(x-5.05), respectively. The interesting results indicate that the J(total) is composed of ionic current J(ion) and electronic current J(e), the pore development and the length of AAO are attributed to the J(ion) rather than the dissolution current, the corresponding J(e) = 4.58 and 5.05 mA/cm(2) contribute to the formation of oxygen bubbles which act as models for the pore formation in 0.3 M and 0.7 M H2C2O4, respectively. This is an efficient and simple method to determine the kinetics of porous anodic oxides. (C) 2017 The Electrochemical Society. All rights reserved.