| Summary: | 碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 106 === High strength low alloy steels have been widely used in the marine engineering and defense industry due to their superior yield strength, toughness and weldability. Although these materials have superior mechanical properties, the corrosion resistance is the other important issue especially when they are used in the marine environment. In this study, we investigated the effect of nickel and copper addition on the corrosion resistance of high strength low alloy steels in the marine environment, and the effect of heat treatments on the corrosion resistance of the new designed NiCu steel. The potentiodynamic polarization curve was conducted using a Gamry Reference 600 potentiostat to evaluate the corrosion performance of two high strength low alloy steels. The surface morphology and composition of corrosion products formed on the material surface after corrosion treatment were analyzed using scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The preliminary electrochemical measurement and surface analysis results showed that higher amount of Ni and Cu addition can improve the corrosion resistance of high strength low alloy steels. In the EPMA analysis, it was found the corrosion layer of higher Cu and Ni containing alloy was enriched with copper. The new designed NiCu steel have the best corrosion resistance at tempering temperature of 660 oC.
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