Corrosion protection performance of stretched graphene-modified cold-sprayed zinc coating for steel rebar

The cold-sprayed zinc technology exhibits unique advantages in the field of metal corrosion prevention due to its environmental friendliness and convenient construction. However, compared to hot-dip galvanizing, there is still a necessity to improve its corrosion resistance. Graphene as a filler material, effectively strengthens the anticorrosive properties of the coating. Nevertheless, the resistance of graphene-modified cold-sprayed zinc coating to chloride ion induced metal corrosion remains unknown. In this study, cold-sprayed zinc coating and graphene-modified zinc coating were employed to steel rebar that was subjected to different levels of tensile stress. The passivation and de-passivation process of the stretched zinc-coated rebar in the simulated concrete pore solution were investigated with electrochemical tests and microscopic analyses. The research findings reveal that compared with ordinary cold-sprayed zinc coating, graphene-modified coating can significantly improve the coating resistance and reduce the corrosion rate of rebar under different levels of tensile stress attributed to the high surface area of graphene. However, due to the discontinuity between zinc powders induced by graphene, a complete passivation film cannot form on the surface of graphene-modified zinc coating, which resulted in a lower resistance against chloride ion induced de-passivation. This study indicates that graphene-modified cold-sprayed zinc-coating is not fit for marine environment.