无溶剂环氧石油沥青涂层在土壤中的降解行为

Deterioration behavior of solvent-free epoxy-petroleum asphalt coating in soil

采用开路电位测量和电化学阻抗谱技术研究了无溶剂环氧石油沥青涂层在不同含水量的土壤中的腐蚀行为,并利用扫描电镜(SEM)对埋设360 d后试样横截面和涂层剥离后Q235碳钢基体表面进行观察,通过X射线能谱仪(EDS)和X射线衍射仪(XRD)对可能存在的腐蚀产物进行分析。结果表明,随着土壤含水量的增加,无溶剂环氧石油沥青涂层的开路电位下降,低频阻抗模值减小,土壤对涂层的侵蚀加剧。400μm厚无溶剂环氧石油沥青涂层在40%H_(2)O+0.6%NaCl土壤中随着埋设时间的延长,低频阻抗模值减小,360 d后为8.15×10^(8)Ω·cm^(2),涂层与金属基体结合良好,没有观察到鼓泡或剥落,将涂层剥离后亦未发现金属基体表面有氧化物、氯化物等腐蚀产物,说明水分和氯离子尚未到达基体表面。无溶剂环氧石油沥青涂层在土壤环境中能形成有效的屏蔽层,对金属基体起到良好的防护作用。

The corrosion behavior of a solvent-free epoxy-petroleum asphalt coating in the soil with different water contents was studied by open circuit potential measurement and electrochemical impedance spectroscopy.The cross section of the specimen buried in soil for 360 days and the surface of Q235 carbon steel substrate where the coating was removed were observed by scanning electron microscopy(SEM).The corrosion products that might form were analyzed by energydispersive spectroscopy(EDS)and X-ray diffraction(XRD).The results showed that,with the increasing of water content in soil,the open circuit potential of solvent-free epoxy-petroleum asphalt coating was shifted negatively and its low-frequency impedance magnitude was decreased,indicating that the soil erosion of the coating was aggravated.The low-frequency impedance magnitude of a 400μm-thick solvent-free epoxy-petroleum asphalt coating was decreased with the extending of burying time in the soil containing NaCl 0.6% and water 40%.After being buried for 360 days,the coating still adhered well to the substrate,free of bubbling and spalling,with a low-frequency impedance magnitude of 8.15×10^(8)Ω·cm^(2),and there did not exist any iron chloride or oxide,indicating that water and chloride ions had not reached the surface of coating/substrate interface yet.As an effective barrier,the solvent-free epoxy-petroleum asphalt coating can provide good protection for metals in soil.