Surface treatment to reduce hydrogen diffusion in steel tanks
Salzgitter Mannesmann Forschung GmbH and the Fraunhofer IST are developing surface treatments as protection against hydrogen embrittlement in ultra-high-strength Type I tanks. The barrier layer is intended to prevent the absorption of hydrogen into the steel material.
Motivation and definition of objectives
Despite very good recyclability, low material prices and economical manufacturing processes, the utilization of steel tanks is currently limited. The reasons for this are the high inherent weights and the tendency of ultra-high-strength steel grades towards hydrogen embrittlement.
The research objective of the project is therefore the development of a hydrogen barrier for tanks made from ultra-high-strength steel tubes. The utilization of these materials enables a reduction in the wall thickness and consequently offers the potential to reduce weight, costs and CO2 emissions.
The Fraunhofer IST is identifying, testing and evaluating potential surface treatments for preventing hydrogen embrittlement. These encompass both surface coatings and modifications which act as a barrier, thereby reducing hydrogen uptake and diffusion.
Salzgitter Mannesmann Forschung is developing a testing device for measuring hydrogen permeation and is verifying the effectiveness of the coating as a hydrogen barrier.
Potential surface treatments:
- Galvanic Zi-Ni coatings exhibit low hydrogen diffusion
- Oxide and nitride modifications of Al, Ti and Cr show permeation values which are lower by two orders of magnitude
The following coating properties have a strong influence on permeation:
- Carbide-to-metal ratio
- Structure of the layer (roughness, morphology, grain size)
- Layer thickness
In the pressure chamber, the gaseous hydrogen is pressed against the disk-shaped material sample at up to 200 bar. On the opposite side is the measuring cell, which detects the escaping hydrogen. In addition, the sample can be elastically loaded, as this can have an influence on the hydrogen absorption. In this way, the penetration of hydrogen from the gas phase can be determined in a steel sample under conditions such as those in a high-pressure tank. The first step is to set up the test apparatus and establish the methodology. The measurement of coated samples makes it possible to determine the barrier effect.
Each partner of the consortium acts in its own name until the Wasserstoff Campus Salzgitter e.V. has been founded.