Determination of Hydrogen in Steel by Thermal Desorption Mass Spectrometry

Hydrogen embrittlement has been observed since high-strength steels have been produced in the nineteen thirties [1,2]. Several different analytical methods have been developed to quantify the total and diffusible hydrogen in steel, but many aspects of hydrogen determination are still to be explored. Purely quantitative determination of hydrogen is not sufficient to fully characterize the steel regarding its resistance against embrittlement. Thermal Desorption Mass Spectrometry (TDMS) allows the investigation of hydrogen absorption and desorption mechanisms to characterize hydrogen traps in different kinds of steel microstructures. This provides valuable information for the development of new materials with a higher resistance against hydrogen embrittlement. Additionally, TDMS allows the quantitative determination of very small concentrations of hydrogen (< 0.1 mu g/g). Such low detection limits cannot be reached with other methods. Due to time-consuming analysis and a rather complex construction, TDMS is usually not applied for hydrogen determination in German steel mills. The present work describes the development of a thermal desorption spectrometer at Thyssen Krupp Steel Europe AG by adapting a compact quadrupole mass spectrometer to a commercially available hot solid extraction analyzer, which has proven to be a simple and efficient solution for the determination of diffusible hydrogen in steel.