The Use of the Electrochemical Permeation Technique to Study Hydrogen Transport and Trapping in Iron

Abstract

The electrochemical technique has become an important tool in studying hydrogen transport in metals. In order to maximize the information obtainable, the electrochemical conditions must be carefully controlled, particularly at the input and output surfaces. Subsequent analysis of the kinetics of consecutive transients can then be used to discriminate between strong (irreversible) and weak (reversible) traps. This approach has been illustrated for iron and a number of iron-titanium alloys, and it has been shown to be possible to model the data to calculate most of the important trapping parameters in such systems.These parameters describe trap populations that can be manipulated to control the extent of some types of hydrogen embrittlement, as illustrated by experiments on a titanium-containing HSLA steel.The permeation technique has also been shown to be useful in detecting the occurrence and extent of dislocation transport of hydrogen in iron. Some of the implications of the effect of such a process on subsequent embrittlement in ferrous and non-ferrous alloys have been assessed.