Development of barrier coatings based on diamond-like carbon for hydrogen storage and transportation

Abstract

The currently employed materials in hydrogen storage and transportation are steels with limited mechanical and hydrogen embrittlement resistance. Therefore, effective and durable barrier coatings capable of withstanding high-pressure hydrogen charging are required to mitigate hydrogen permeation, protect the pipe or tank material and thus enhance its overall performance. In this regard, hydrogenated amorphous Diamond-Like Carbon (a-C:H) coatings with adhesion-promoting Cr and WC interlayers were designed in this work by means of Physical Vapor Deposition (PVD) and Plasma-Enhanced Chemical Vapor Deposition (PECVD) technologies. Films with different thicknesses ($\approx 500\text{nm}$, $\approx 1000\text{nm}$ and $\approx 2500\text{nm}$) and hydrogen contents (around $20\text{\%}$ and $30\text{\%}$) were produced so as to assess the effect of both variables on their barrier performance. The coatings were subsequently applied to AISI 4130 low-alloyed carbon steel substrates. Afterwards, their evaluation as hydrogen barriers was carried out by means of a Devanathan–Stachurski electrochemical permeation setup, a liquid-phase technique that accurately measures hydrogen permeation and diffusion. All coatings demonstrated effectiveness as hydrogen barriers. Thickness proved to be critical to ensure repeatable outcomes, while more hydrogenated films exhibited higher diffusivity. In fact, the thickest coatings ($\approx 2500\text{nm}$) with the lowest hydrogen content (around $20\text{\%}$) outperformed the others, reducing hydrogen diffusion by a factor of 22, and permeation by a factor of 179. Considering the results, DLC coatings will likely pave the way for the development of a new generation of facilities for mass transportation and storage of hydrogen.