Influence of Frictional Heat on Hydrogen Permeation Measurements

Abstract

Hydrogen transport properties in metals are often investigated in electrochemical Devanathan-Stachurski double cells (DS) or modifications thereof. A DS setup consists of input and output cells which are divided by a metal membrane. The hydrogen oxidation current measured in the output cell is proportional to the permeation rate of hydrogen through the metal membrane. In certain applications of lubricated tribocontacts, steel is susceptible to damages by uptake of hydrogen. For investigation of the friction-generated hydrogen uptake a lubricated sliding contact in the input cell of the DS setup is realized.Related low hydrogen permeation current signals are significantly affected by the steel membrane temperature. As an example, frictional heating of the steel membrane leads to additional release of residual hydrogen from the steel. To investigate the temperature effect, tests with an oil containing a hydrogen promotor, a PFPE oil and without lubrication were conducted. The results indicate that the permeation signal is strongly influenced by frictional heating. Such measured currents must not be misinterpreted as hydrogen generated by lubricants. A thermodynamic and kinetic model of the hydrogen diffusion and trapping reveals the correlation between current signal and temperature change.