Fabricate Metal Oxide PH Microelectrode By Powder Pressing Method

A lot of metal materials were used in marine environment with the development of ocean engineering. The metal material corrosion occurs easily in the marine environment which has the characteristics of high salt, high Cl- concentration. Some characteristics of metal material such as toughness, mechanical strength would be changed when metal material corrosion especially local corrosion occurred. It triggered many industrial accidents and casualties. The H+ distributed on the surface of metal material would change when the local corrosion occurred. Hence, the local corrosion could be monitored though monitoring the distribution of H+.The pH electrode was briefness method to monitor the value of pH. The pH electrodes needed to meet the requirement of wear-resisting, easy miniaturization when they were used to monitor the change of pH on the metal surface micro zone in marine environment. The glass electrode most commonly used could not apply in this environment due to low mechanical strength, difficult to miniaturization. The metal/metal oxide pH electrode was a kind of all solid-state electrodes with excellent performance and it could be used in harsh conditions. Powder pressing method was used for the preparation of Ag/AgCl reference electrode and it had the advantages of high efficiency, simple operation, strong controllability et al. In this paper, the powder pressing method was used to fabricate tungsten oxide pH electrode and Sb/Sb2O3 pH electrode. It was expected to be used for monitoring metal local corrosion. The main research works and results are as follows:In this paper, the tungsten oxide pH electrode and Sb/Sb2O3 pH electrode were fabricated by powder pressing method. The performances of those electrodes were evaluated with potentionmetric method, polarization curve, cyclic voltammetry and current interruption method. Those electrodes were used to measure the pH value of solutions.The best conditions for preparation of tungsten oxide pH electrode were to control the pressure of 6 MPa and holding time of 5 min. The response time of this electrode was about 100 s. This electrode was adapted to the pH range from 1.0 to 7.0, had excellent ability of anti ions interference and reversibility. The measurement error between this electrode and glass electrode was close to 0.1 pH. The conditions for preparation of Sb/Sb2O3 solid pH electrode were optimized to control pressure of 8 MPa and holding time of 5 min. The optimum formula component of the electrode was Sb:Sb2O3:Graphite=2:2:1. The response time of electrode was about 200 s. This electrode was adapted to the range of pH 1.0-5.0, had excellent anti ions interference capability and reversibility. The measurement error between this electrode and glass electrode was close to 0.05pH.Tungsten oxide pH electrode and Sb/Sb2O3 solid pH electrode all could be prepared by powder pressing method. Two electrodes were influenced by the adsorption effect of graphite as binder though mechanism research.The response slope was less than the theoretical slope. The response mechanism of tungsten oxide pH electrode was complicated due to the existence of hydration layer. The using pH range of tungsten oxide pH electrode was wider than Sb/Sb2O3 solid pH electrode. The Sb/Sb2O3 solid pH electrode had excellent reversibility and anti ions interference ability than tungsten oxide pH electrode. The measurement error was smaller than tungsten oxide pH electrode. The Sb/Sb2O3 solid pH electrode was more suitable for measuring the pH value of solution.