关键词: PAEP涂层, 电化学阻抗谱, 湿热环境, 失效行为

Abstract: 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.

Key words: PAEP coating, EIS, humidity environment, failure behavior