Corrosion performance of arc-sprayed Zn coating in simulated acid rain environment

Hot-sprayed Zn coating has been widely used in many industrial fields because of its excellent corrosion resistance and coating performance.It has become one of the effective measures to prevent corrosion of metal materials in outdoor working environment.In order to study the corrosion behavior of hot-sprayed Zn coating in acid rain, hot-sprayed Zn coatings on Q235 carbon structural steel were prepared by arc spraying technology.Surface morphology, corrosion product, hardness and corrosion rate of coatings were studied by means of scanning electron microscopy(SEM), X-ray diffraction(XRD), hardness test and weightlessness analysis in simulated acid rain for different pH.The results showed that surface corrosion of Zn coatings were increase with decrease of pH value of simulated acid rain solution, corrosion products on the surface of Zn coatings increased, morphology gradually changed from small block to pinnate and island, and the main components were Zn(OH)2, ZnSO4 and Zn4SO4(OH)6·3H2O.The maximum surface hardness of coatings was 23.4 HV, and the minimum corrosion rate was 0.21×10-4 g/(m2·h).However, when pH value of simulated acid rain solution decreased from 7 to 2.8, surface hardness of coatings decreased about 12%, and corrosion rate increased to 26 times of the minimum value.When pH value of simulated acid rain solution ranged from 5 to 2.8, corrosion of Zn coatings was more serious.