Study on Corrosion Protection of Q235 Steel in Simulated Soil Pore Solution by Different Electrodeposited Coatings

Q235 steel as power grounding material was selected as the substrate, and different coatings (Zn-Ni alloy coating, Zn-Ni-W alloy coating and Zn-Ni-W/ZrO2 composite coating) were electrodeposited on its surface. The corrosion behavior of Q235 steel and different electrodeposited coatings in simulated soil pore solution was investigated through electrochemical testing. The results show that Zn-Ni alloy coating, Zn-Ni-W alloy coating and Zn-Ni-W/ZrO2 composite coating can inhibit the corrosion process of Q235 steel in simulated soil pore solution to improve its corrosion resistance. The phase composition of Zn-Ni-W alloy coating is the same as that of Zn-Ni alloy coating, while Zn-Ni-W/ZrO2 composite coating contains Zn phase, Ni5Zn21 phase and ZrO2 phase. ZrO2 particles are uniformly doped in the composite coating. Compared with Zn-Ni alloy coating and Zn-Ni-W alloy coating, Zn- Ni-W/ZrO2 composite coating has the lowest corrosion current density (9.87x10-7 A/cm2) and the highest charge-transfer resistance (7.34×103 Ω·cm2). After being corroded by 15 mA DC stray current for 14 days, it still maintains integrity and high compactness with lightest corrosion degree. Electrodeposition of Zn-Ni-W/ZrO2 composite coating can not only meet the electrical conductivity requirements of power grounding electrode, but also significantly improve the corrosion resistance of carbon steel grounding electrode under the combined action of electrochemical corrosion and stray current corrosion in soil.