Hydrogen in metals is a topic of great importance in materials science. Its presence in metals may be desirable or undesirable. For instance, hydrogen may become an energy carrier of the future. If so, its production, controlled storage and release, as well as its safe transport will become crucial issues. For this application hydrogen uptake into metals, to form metal hydrides, and its release from these hydrides should be as effective as possible. However, in most cases hydrogen in metals is an unwanted impurity, as even in very low concentrations it can cause the so-called hydrogen embrittlement in many steels and other alloys, which constitutes a serious safety and performance problem, e.g., in constructions, planes and medical implants.
Hydrogen embrittlement may result in fractures delayed by days or even months. For an in-depth understanding of the underlying phenomena, it is crucial to realize reliable detection of hydrogen at ultralow concentrations, well below the parts per million (ppm) range. Hydrogen can be taken up by the metal during its processing, e.g. during annealing, pickling or other cleaning steps, but also at later stages during its application, such as due to corrosion or cathodic corrosion protection. Therefore, it is important to develop sensitive techniques of measuring hydrogen uptake and diffusion, as well its presence in trap sites in the material.
At MPIE we successfully developed a Kelvin probe based technique for measuring hydrogen in and its permeation through steel and other alloys with a so far unachieved sensitivity and high spatial resolution [1-4].
Currently several projects are being carried on characterisation of hydrogen in different steel grades and other alloys, as well its uptake and permeation. Even hydrogen uptake through zinc coatings can be measured (see e.g. [4]).
