Effect of sealing treatment on corrosion resistance of zinc-calcium phosphate coating prepared on HRB335 rebar in simulated concrete pore solution

Abstract

In order to reduce the corrosion of HRB335 rebar in a concrete environment and ensure the service life of reinforced concrete structures, a zinc-calcium phosphate coating was prepared on the surface of HRB335 rebar. The dehydration antirust oil, chromate solution, and silicate solution were used for the sealing treatment of the phosphate coating. The experimental results show that the zinc-calcium phosphate coating possesses many compact and spherical particles, which evenly and completely cover the surface of rebar substrate. The surface morphology, thickness, composition and corrosion resistance of the phosphate coating do not change significantly after sealing treatment in dehydrating antirust oil. However, sealing treatment in chromate solution and silicate solution can block the intergranular pores, improve the compactness and change the composition of phosphate coating to enhance the corrosion resistance of phosphate coating in simulated concrete pore solution. The main composition of the phosphate coating after sealing treatment in silicate solution are Zn, Ca, P, O, C and Si elements, and the compactness is slightly better than that of the phosphate coating after sealing treatment in chromate solution. Compared with rebar substrate, the corrosion current density of the phosphate coating after sealing treatment in silicate solution is reduced by nearly two orders of magnitude, and the protection efficiency toward rebar substrate reaches 98.2 %, which can enhance the corrosion resistance of rebar substrate in simulated concrete pore solution for a long time. Silicate solution is less harmful to the environment and has a good sealing effect, so it has potential application in the sealing treatment of phosphate coating.