| Hot-dip aluminized and galvanized steel are widely used in water environment because of their corrosion resistance and mechanical property. Usually, hot-dip steel wires coated by polyvinyl chloride (PVC) are applied in underwater cable engineering to isolate the metal from corrosive environment. With time, the solution goes through the cracks and corrodes the metal. However, because of PVC coating, the corrosion products can't peel and form saturated solution in the cracks, and then form a kind of closed corrosive environment, which will affect the corrosion behavior. The main work in this paper is summarized as follows:(1) Flux method was adopted as pretreatment method of hot-dip RE-Al process, with proper technical conditions: temperature was 720℃and time was 30 s. The hot-dip coating was proved to be qualified after checking the surface quality.(2) The corrosion behavior of hot-dip RE-Al steel in seawater, Al(OH)3-seawater, freshwater and Al(OH)3-freshwater was investigated through immersion test, polarization curve, Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron Microscopy (SEM). The results showed that Al(OH)3 could accelerate the corrosion rate of samples in freshwater and seawater. With time, corrosion resistance decreased in Al(OH)3-freshwater and Al(OH)3-seawater, because the pitting corrosion was aggravated. Then the corrosion behavior of RE-Al coating in Al(OH)3-seawater of different temperatures and in saturated Al(OH)3 solution of different Cl- concentrations was studied. It was showed that corrosion current density firstly decreased and then increased with the rise of temperature. When temperature was 40℃, current value was least, and the corrosion resistance was best. The result of the immersed samples in different Cl- concentration solution indicated that the maximum corrosion current density was obtained at 4%.(3) The corrosion behavior of galvanized steel in seawater, Zn(OH)2-seawater, freshwater and Zn(OH)2-freshwater was investigated through immersion test, polarization curve, EIS and SEM. The results showed that Zn(OH)2 could accelerate the corrosion of samples in freshwater and seawater. With time, corrosion resistance was reduced in Zn(OH)2-freshwater and was enhanced in Zn(OH)2-seawater. Then the corrosion behavior of galvanized coating in Zn(OH)2-seawater of different temperatures and in saturated Zn(OH)2 solution of different Cl- concentrations was studied. It was showed that the corrosion resistance of coating was reduced with the rise of temperature. When temperature reached 50℃, corrosion current changed obviously and corrosion resistance was the worst. This indicated that the breakdown of the corrosion products layer occurred on the coating. The result showed that when Cl- concentration was less than 1%, the corrosion current density increased with increasing Cl- concentration. Then the current density decreased and tended to be stable.
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