Abstract: This paper introduces the application of a duplex stainless steel used in circulating water pump in a coastal power plant, and points out that the cause of failure was the loose of fasteners caused by crevice corrosion between parts. By the processing of welding the crevice corrosion was eliminated. Some other protective measures are also proposed. The results show that the corrosion resistance of duplex steel is fairly strong, but not absolutely. When it is used in coastal power plant. it should be pay attention to the protection.