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.