Effect Of Hydrostatic Pressure And Alternating Pressure On Degradation Of Epoxy Coating

The metals can easily corrode in deep-sea environment, and a major protection is to using the organic coatings. Electrochemical impedance spectroscopy (EIS) has been widely utilized to investigate the corrosion process of organic coatings systems, due to its ability to provide the information of the degradation of the coatings and the corrosion process on the metal/coating interface.Seawater pressure is an important factor which influences the corrosion failure of materials in deep-sea environment.The present paper selected two kinds of epoxy coating which are commonly used in the marine environment as research objects, the failure process of the coating and the corrosion behavior of the metal under the coating at hydrostatic pressure or alternating pressure were studied by using electrochemical impedance spectroscopy combined with water absorption and adhesion of the coating variation with immersion time,the effect of hydrostatic pressure and alternating pressure on the failure behavior of the coatings were studied. The results revealed that the hydrostatic pressure greatly affected the failure process of the coatings. The diffusion rate of the electrolyte solution through the coatings was accelerated in the solution at high hydrostatic pressure. Compared with the case under atmospheric pressure, at high hydrostatic pressure the coating resistance was reduced,the charge-transfer resistance was decreased, metal corrosion reaction was accelerated; the protection properties of the coating was deteriorated. Under alternating pressure the protection properties of the coatings was reduced obviously, the metal corrosion happened. After that, the coating performance changed periodically, as well as the metal corrosion. Compared with the case under atmospheric pressure, the corrosion resistance of the coating decreased rapidly, the corrosion reaction was accelerated after pressure increasing. Under hydrostatic pressure or alternating pressure, the water absorption of the coating increased and the adhesion of the coating decreased with immersion time, the performance of the coating decreased gradually.