The formation behavior of the blister in electro-galvanized steel was studied by simulating the zinc-deposited specimen in the laboratory. The micro-crack and delamination were artificially introduced at the interface between the zinc layer and steel substrate. The steel surface is mechanically polished or contaminated with oil to introduce cracks or delamination after zinc coating. Hydrogen charging was applied in the solution under the bias condition of 20 mA/cm2. Blister formation was identified on the surface of the zinc-coated steel after the hydrogen charging. The expansion of the interface crack was identified in the cross-sectional image of a blister. Through TOF-SIMS experiments, hydrogen ion and methane ion were measured inside the blisters. The blister was generated by hydrogen and methane gas.

Further hydrogen charging and thermal desorption test reveal the role of hydrogen diffusion in the steel substrate and zinc layer on the blister formation. The baking treatment results in the formation of a blister at the zinc/steel interface under specific conditions. The blister formation mechanism is discussed by the obtained results.