Effect of Nickel Co-Deposition Amount in Zn-Ni Alloy Plating on Hydrogen Embrittlement of High Strength Steel

Abstract

A method of using three-point bending tests to evaluate hydrogen embrittlement was applied to clarify effects of nickel co-deposition amounts in Zn-Ni alloy electroplating on hydrogen embrittlement of SK85 steel sheets. Hydrogen embrittlement occurred in all plating immediately after plating, irrespective of the nickel co-deposition amount. Diffusive hydrogen, which is responsible for hydrogen embrittlement, was detected in each plated specimen before baking at around 200 ℃. That finding is consistent with hydrogen embrittlement results. However, after baking, diffusible hydrogen at nearly 200 ℃, which is responsible for hydrogen embrittlement, was desorbed from all specimens. These results, which demonstrate that zinc plating without detectable diffusible hydrogen exhibits hydrogen embrittlement, support the hydrogen vacancy cluster theory: hydrogen absorbed during plating generates hydrogen vacancy clusters, which form voids and engender fracture.