Corrosion mechanism and coating optimization of steel in tower connection sections under high humidity environment

To address the pronounced corrosion and strength degradation of steel in wind turbine tower connections under high-humidity chloride exposure,this study aims to elucidate the corrosion-mechanical deterioration mechanism of Q345E steel and to optimize representative protective coating systems by comparative evaluation. Q345E low alloy steel was selected to systematically study the corrosion behavior and protective coating performance in high humidity environment through electrochemical testing,mechanical property analysis and corrosion product characterization. In a Na Cl solution with a mass fraction of 3.5%,a relative humidity of 95%,a temperature of 60 ℃,the thickness variation of the steel corrosion layer slowed down after 168 h,eventually reaching 40.4 μm,and the depth of the corrosion pit increased to 12.7 μm. Tafel polarization and EIS results show that I_corrincreased from 3. 4 μA/cm² to 8.2 μA/cm² in the early stage of corrosion（0-168h）,and the corrosion rate decreased after 168 h due to the coverage of corrosion products. Compared with different protective coatings,nano-ceramic reinforced thermal sprayed zinc（NC-TSZ） performed best,with an initial R_ct value of 478. 2 Ω·cm²,and it still maintained 289. 4 Ω·cm² after 1 800 h of corrosion,a decrease of 39.5%. Mechanical tests show that after 1 800 h of corrosion,the tensile strength of the steel dropped from 510.4 MPa to 432.7 MPa,and the elongation dropped from 24.5% to 14.1%,indicating that corrosion caused the material to become brittle. Studies have shown that chloride ion erosion accelerates the corrosion process,and optimizing the NC-TSZ coating can effectively improve the corrosion resistance of steel,thereby improving the long-term service stability of wind turbine towers under high-humidity conditions.