Investigation On Hydrogen Permeation Sensor With Gelatiniform Electrolyte And Anodization Additive Of Magnesium Alloys

Hydrogen sensors can be used for online monitoring hydrogen permeated in steels owing to a corrosive reaction and other process of hydrogen evolution. It is significant to ensure safe operation of equipment and to decrease economic losses through online-monitoring hydrogen permeation.Based on the method of electrochemical hydrogen permeation detection presented by Devanathan-Stachurski, potentiostatic electrolyte-type and galvani-cell type hydrogen sensors have been developed to determine the permeation rate of atomic hydrogen. The effect of plating nickel time and oxidation potential on rate of hydrogen permeability were investigated. The catalytic coating of atomic hydrogen oxidation on the detected steel surface was obtained via plating nickel for 5 minutes. Permeation curves measured by potentiostatic electrolyte and galvani-cell hydrogen sensors at the same experiment condition were consistent, which were independent of the modes of imposed potentials.Sodium polyacrylate (PAAS) and carboxyl methyl cellulose (CMC) as thickener and water retention agent. They were added to potassium hydroxide (KOH) solution to prepare the alkaline polymer electrolyte of PAAS-CMC-KOH-H2O. The effects of polymer concentration on the electrolyte conductivity, viscosity and permeaton rate were investigated. When the polymer composed of sodium polyacrylate and carboxyl methyl cellulose (ratio 5:1) was added in 0.2 mol·dm-3 KOH, electrical conductivity decreased, but viscosity increased gradually with the increase of the polymer concentration. The colloidal electrolyte containing 50 wt% polymer content had suitable viscosity, high electrical conductivity. At normal temperature, water is evaporated in very slow rate. it had good water-retained performance. The consistent permeation curves were detected by the sensor of the colloidal electrolyte or the liquid KOH electrolyte, respectively.The effect of triethanolamine concentrations on anodizing film of AZ91D magnesium alloy was investigated through using the technique of constant current anodizing in the bath containing KOH, Na2SiO3, Na2B4O7 and triethanolamine etc. Voltage-time curve, immersion corrosion experiment and polarization curves were used to valuate the properties of the anodizing coatings. The coating morphology was characterized by SEM. The research results show that triethanolamine had remarkable effect on restraining arc, increasing the thickness of film, decreasing sizes of surface micro-holes and improving surfacefinish. The coating obtained by anodic oxidation in the solution containing 30 g·dm-3 triethanolamine dsiplayed good corrosion resistance. During the anodic oxidizing of magnesium alloy, triethanolamine molecules chemically adhered to the surface of the magnesium alloy. The adsorption strength and adsorption capacity of oxygen bubbles on the electrode surface were decreased during the micro-arc oxidation so that the porosity of micro-arc oxidation ceramic coating was reduced, and the coating compactness and corrosion resistance increase.