The Research Of Coating's Corrosion Behavior In Deep-sea Environment Basedon The Wire Beam Electrode

The organic coating is currently widely used in deep-sea environment for corrosion protection. However, the defected surface of organic coating can lead the metal substrate corroded preferentially. Therefore, It is necessary to study the corrosion behavior of the defected organic coating in the deep sea environment. In this paper we studied the corrosion behaviour of the organic coatings in deep-sea environment, which is impacted by defects and fillers. WBE and EIS combine with water absorption and other macro methods are used in the paper. The main works of this paper include:(1) Combined the wire beam electrode and electrochemical impedance spectroscopy to research the corrosion of the defected coating. The feasibility and reliability of the combination was studied. Through using the wire beam electrode and electrochemical impedance spectroscopy in normal pressure, an organic coated wire beam electrode surface with an artificial defect was studied. The defect size is 1mm × 3mm. The electric potential,current and frequency of 1 Hz single-frequency impedance of the 100 wire electrodes were tested. By comparison with experimental data and macro photographs, the reliability of the combination of tow electrodes and electrochemical impedance spectroscopy technique was determined.(2) Through testing the single frequency independence of epoxy coating and defected epoxy coating in normal pressure, the process that the protection of the coating performance decreased from the defection and diffused constantly was monitored, which is consistent with the EIS data. The coating without defection had the preferable protection performance. The existence of defection merely accelerates the coating failure, instead of losing protective effect completely.(3) The single-frequency impedanceof the coatings at 6MPa hydrostatic pressure and atmospheric pressure are studied. It was obtained that the area of the color on behalf of low impedance modulus value increased rapidly at 6MPa hydrostatic pressure. The result shows that the existence of hydrostatic pressure accelerated the coating physical failure, which is in good agreement with the EIS results. From single frequency impedance data, it was obviously proved that the existence of the hydrostatic pressure more effectively accelerated the defected coating physical failure.(4) the addition of aluminum tripolyphosphate slows down the process of the failure of the coating by the change of the color area representing each impedance modulus value in the single frequency impedance graph, which is consistent with the EIS results, and the main protective location of the aluminum tripolyphosphate is the weak coating itself and artificial defect. Among of them, the protective effect to the defect coating in hydrostatic pressure raises obviously according to the addition of aluminum tripolyphosphate.