The failure analysis of coatings can provide an important basis for the selection of anti-corrosion materials and the formulation of anti-corrosion schemes.A portable microscope was used to observe the macroscopic defects of coatings.The microscopic defects of coatings were determined by the"tape paper pulverization grade evaluation",the Fourier Transform Infrared Spectroscopy(FT-IR)and the Electrochemical Impedance Spectra(EIS).The surface hydrophobicity of coatings was measured by a simplified contact angle method.The results show the coatings have macroscopic defects such as hole defects caused by the bursting of inclusion bubbles and the falling off of fillers,crack defects caused by the mismatch of thermal expansion coefficient of coatings/substrate,and crack defects caused by collision and bending.After exposure for a certain time,the degradation and photoaging of the coatings film leads to the microscopic defects.The newly applied coatings material has certain hydrophobicity,and the hydrophobicity decreases rapidly after exposure to industrial marine atmospheric environment.The retained liquid water on the surface of coatings dissolves the soluble salt in the dust,and absorbs salt particles and oxygen in the atmosphere.The electrochemical corrosion of steel initiates when the retained liquid water reaches to the coatings/metal interface through the macro and micro defects of the coatings.The accumulation of corrosion products at the coatings/metal interface results in the bubbling,cracking,peeling off and failure of coatings.
维普
万方数据