Development Of A New Electrochemical Hydrogen Permeation Probe

Based on the method of electrochemical hydrogen permeation measurement presented by Devanathan-Stachurski, we developed a new hydrogen sensor to determine the concentration of atomic hydrogen in metals. The open circuit potential change of Nickel electrode in 0.2mol/LNaOH solution was investigated. Nickel electrode (99.99%) can be used as a reference electrode for the hydrogen sensors because it can stability at -0.205V in 0.2mol/LNaOH solution after about 100 seconds, and the potential fluctuation was in the range 0.1 to 0.2mV. The alkaline gel-electrolyte of PVA-CMC-NaOH-H2O was prepared by mixing polyvinyl alcohol and sodium carboxymethyl cellulose with different mass ratio in 0.2mol/L NaOH solution, The effects of gel-electrolyte concentration on the electrical resistance,viscosity and passive potential rangewere investigated. When the gel-electrolyte composed of 32g polyvinyl alcohol and 7.5g sodium polyacrylate (ratios4:l) was added in 350ml 0.2mol/L NaOH, the electrical resistance and passive potential range were close to those in 0.2mol/L NaOH, and the viscosity was moderate well. So, the gel-electrolyte was used for replacing the liquidity and corrosive NaOH solution in hydrogen sensor. The use of transient potential method for hydrogen permeation measurement can eliminate the influence of thickness of the measured specimen, the responding transient current was large, and so the transient potential method in measuring hydrogen permeation current for thicker specimen has a high sensitivity. Field tests using CST820 hydrogen sensor designed on the transient method revealed that the new electrochemical hydrogen permeation probe has several advantages including simplicity, high sensitivity and high reliability.