12th International Conference on Zinc & Zinc Alloy Coated Steel Sheet - GALVATECH 2021

Hydrogen embrittlement of advanced high strength steels (AHSSs) in atmospheric exposure conditions is of utmost importance for automotive industry as the application of AHSSs grows steadily due to desirable mechanical properties. Different aspects of the hydrogen embrittlement phenomenon such as hydrogen entry caused by atmospheric corrosion reactions are currently under intensive research.
This study was focused on understanding the effect of atmospheric climatic and exposure conditions on atomic hydrogen formation, entry and diffusion in bare and zinc coated AHSSs. Several complementary techniques allowing for in situ investigation of hydrogen entry and permeation through complex phase and dual phase AHSSs and their mechanical properties have been employed on bare steel and zinc coated specimens with artificial defects. KircTec sensor is a new device for hydrogen permeation measurements based on monitoring of electric resistance changes. One side of a steel specimen was exposed to wet-dry cycling conditions in a corrosion chamber after application of sodium chloride solution in order to induce atmospheric corrosion, while hydrogen content was measured by the KircTec sensor attached to the opposite side. Scanning Kelvin Probe Force Microscopy (SKPFM) measurements with lateral resolution allowing for identification of permeation paths and the effect of microstructure as well as scanning Kelvin probe (SKP) measurements were conducted using a similar setup, recording changes in contact potential difference in controlled atmospheres. The effect of atmospherically induced hydrogen on mechanical properties of AHHSs was assessed by a Slow Strain Rate Test (SSRT) in real time.
The paper will present results on the effect of wet-dry cycling, presence of corrosion products, zinc coating as well as on the mechanism of atomic hydrogen entry.