聚天门冬氨酸酯聚脲涂层湿热失效行为的电化学

Failure behavior of polyaspartic ester polyurea coating in humidity environment by EIS

采用电化学阻抗谱研究了聚天门冬氨酸酯聚脲涂层在湿热环境作用下的失效行为,采用SEM研究了聚天门冬氨酸酯聚脲涂层失效前后表面形貌的变化。电化学研究结果表明:涂层湿热失效过程分为3个主要阶段:前期电解质在涂层中的渗透、中期基体金属腐蚀发生起始的过渡、后期基体金属的腐蚀扩展并导致涂层的失效。湿热试验中,涂层孔隙率和涂层吸水率均呈3个阶段变化,即快速增长阶段、缓慢增长阶段和稳定阶段,很好地验证了PAEP涂层湿热失效的3个过程。表面形貌研究发现,湿热试验4572h后,涂层表面粗糙度增加,出现了裂缝等缺陷,表明涂层已经失去防护作用。

Failure behavior of polyaspartic ester polyurea（PAEP）coating in humidity environment was studied by means of electrochemical impedance spectroscopy（EIS）and scanning electron microscope（SEM）.A series of impedance spectra of PAEP coating during humidity experiment were measured,and the protection properties of the coatings were evaluated according to the spectra.Equivalent circuit models were proposed to interpret the electrochemical impedance data for the present coated systems.The protection properties of the coatings were evaluated and analyzed by electrochemical specific parameters of coating（water absorption and porosity）.The experimental results indicated that coating failure behavior could be divided into three main stages：firstly,permeability of electrolyte to the coating;secondly,initial transition of base metal corrosion reaction;thirdly,coating failure due to aggravated corrosion of metal matrix.Then water absorption and porosity of polyaspartic ester polyurea coating were used to evaluate the coating aging performance,and the result showed that both changes presented three stages：rapid growth stage,slow growth stage,and stable stage.From the beginning 24 h of humidity experiment to 4752 h,water absorption increased to 0.216% from initial 0.046%,and porosity increased to 2.32×10-5 from initial 2.31×10-9.SEM images of coating surface showed that roughness of coating surface increased and defect of fracture appeared after 4572 h of humidity experiment,indicating the failure of coating.