Zn–Ni alloy plating from sulfuric acid baths has excellent hydrogen embrittlement resistance for high strength steels. In this study, we investigated the
factors that contribute to the hydrogen embrittlement resistance of Zn–Ni alloy plating. In Zn–Ni alloy plating, microcracks are formed in the coating. Hydrogen
embrittlement was accelerated by mechanical sealing of these microcracks, and the microcracks that form in the coating were a pathway for hydrogen release.
Therefore, these microcracks are found to play an extremely important role in suppressing hydrogen embrittlement. It is suggested that a gap in the plating film
that can release hydrogen–induced vacancies is important to suppress hydrogen embrittlement due to plating.