Hydrogen Embrittlement Behavior of Zinc Electroplated High Strength Steel and the Effects of Silica Codeposition

Abstract

The hydrogen embrittlement of 145kgf/mm²-class high strength steel was evaluated, with the concomitant measurement of hydrogen absorbed during pretreatment and zinc plating of the steel using zincate bath with or without suspended silica particles. It was found that almost all of the absorbed hydrogen was located in the plated zinc layer and at the zinc/steel boundary layer of a thickness of less than 100μm. During a series of tensile tests conducted using a notched tensile test piece at strain rates of from 4.2×10^-5 to 4.2×10^-3sec^-1, a clear relationship was established between hydrogen content and tensile strength. Thus it was concluded that the tensile test can be used as a quick method of evaluating hydrogen embrittlement. When 0.018μm silica particles were codeposited with zinc in an amount of only 0.2wt%, the notch-tensile strength as well as elongation were much greater than with plain zinc coated steel. This effect may be ascribed to the dispersed particles lowering the diffusion barrier height for hydrogen diffusion.