Application of Cyclic Thermal-Oxidized IrOx Electrode in pH Detection of Interface Region of Zn/Steel Galvanic Process

Abstract

Previously, a cyclic heating and quenching process for developing IrOx electrodes is proposed. The fabricated IrOx electrodes show excellent comprehensive properties including wide E-pH range, near Nernst pH sensitivity, fast response rate, and long term stability etc. In this work, the IrOx electrodes are applied in the detection of surface pH changes during galvanic corrosion process of Zn/Steel couple in thin electrolyte film and bulk solution respectively. This detection is realized by integrating the self-fabricated IrOx pH sensor and self-built moving platform together. Before the application of the IrOx electrode, the appropriate way of scanning the surface of the Zn/steel galvanic couple is discussed. Comparing with the case in bulk solution, the Zn/steel couple corrodes faster in 1mm electrolyte layer, the surface pH of which increases to a high value after corrosion begins for 20~40min, and the low pH region exists on the zinc surface and the region adjacent to border area of the steel surface, whereas the pH value of the steel surface away from the border area is relative high. It is demonstrated that the IrOx electrode could detect the pH distribution effectively in surface region during metal corrosion, which could help the understanding of corrosion process under different situations.