Q235钢表面环氧复合涂层在变电站环境中的腐蚀行为分析

以Q235钢表面涂覆的环氧富锌底漆,水性聚氨酯中间漆,银灰环氧磁漆构成的环氧复合涂层为对象,研究变电站环境中涂层自然暴露18个月后的腐蚀行为,并将其与用5%NaCl溶液浸泡250天处理的涂层的腐蚀行为做对比。采用电化学阻抗谱(EIS)研究环氧复合涂层试样的电化学腐蚀行为,评价环氧复合涂层的耐候性与耐盐性,并通过FT-IR表征涂层浸泡和自然暴露过程的结构变化。结果表明,环氧复合涂层试样在5%NaCl溶液中浸泡250d后,涂层阻抗从3.967×10~9Ω·cm2降至9.780×10~2Ω·cm~2,其失效机制为腐蚀介质通过涂层微孔逐渐渗入涂层中形成微观电通路,导致涂层孔隙率逐渐增大,基底材料腐蚀加速;自然暴露试验18个月的试样,其涂层阻抗为2.708×10~6Ω·cm~2,防护性良好。

The corrosion behavior of Q235 steel spraying epoxy composite coating in substation environment

The epoxy composite coating composited by zinc rich epoxy primer,waterborne polyurethane intermediate coating and silver epoxy enamel was sprayed on the surface of Q235 steel.The anticorrosion of as-prepared samples in substation environment with atmospheric exposure for 18 months,and in 5％ NaCl aqueous solution for 250 days were evaluated and compared,respectively.Electrochemical impedance spectroscopy(EIS) was employed to analyze the corrosive behavior of epoxy composite coating in 5％ NaCl aqueous solution,the weather and the salt resistance were also evaluated.Additionally,the structure changes of the epoxy composite coating induced by salt immersion and atmospheric exposure were characterized by Fourier transform infrared (FT-IR).The results are demonstrated that the epoxy composite coating is corroded to be invalid after immersed into 5 ％ NaCl aqueous solution for 250 days,and the impedance decreases from 3.967 × 109 Ω · cm2 to 9.780 × 102 Ω · cm2.The mechanism of corrosion is the corrosive medium gradually penetrates into the composite coating to form micro electric circuit through micro pores,resulting in the increase of porosity and corrosive rate for the composite coating.However,the impedance of epoxy composite coating in substation environment for 18 months is still 2.708 × 106 Ω · cm2,indicating good corrosion resistance.