Erosion-corrosion Of90/10Alloy In Artificial Seawater

With the development of the times, population growth， resource shortages andenvironmental degradation the three major problems getting worse. In recent years, in orderto alleviate these three problems, world increasingly turning their attention to marine whichhave vast space and rich resources, and engaged in a fierce battle for resources. Exploration,development and utilization of marine have become the consensus of the world.Marine environment is very harsh, material inevitably occur severe corrosion in seawater,the most severe of which is erosion-corrosion, especially in the case of sediment erosion ismore serious. In order to adapt to the harsh environment, materials gradually from carbonsteel and cast iron which have poor corrosion resistance into copper-nickel alloy which havegood corrosion resistance.In this paper, the study object is90/10copper-nickel alloy, using self-made jet devicessimulate the marine environment. Electrochemical impedance spectroscopy, potentiodynamicpolarization curves and electrochemical noise testing technology were employed to monitorthe corrosion behavior of90/10copper-nickel alloy under different conditions, combinedcorrosion morphology and composition analysis, discussion of the influence of theerosion-corrosion of90/10copper-nickel under velocity, impact angle and sediment. Theresults showed that:(1)In the initial soaking(0-2d), the oxygen of seawater promotes the formation ofcorrosion product film, but the formation speed is slow, the oxygen which to participate in thecathodic reaction diffusion gradient exists, the corrosion reaction controlled by diffusion, inthe low frequency zone of EIS displays diffusion; In the mid-term soaking(2d-20d), graduallyform a stable dense corrosion product film; In the late-term soaking(20d-90d), gradualformation of the outer and inner layers of film in the surface. In the long-term immersion, theoccurrence of localized corrosion, corrosion pits formed on the surface, with the immersiontime, the etch pits is gradually increasing.(2)In flowing seawater, due to the mobility of seawater, increase the oxygen diffusioncoefficient and charge transfer rate, thus contributing to the anodic and cathodic reactions, thecorrosion is accelerated. The mobility of water promote anode reaction, the speed ofcorrosion product film formation and dissolution is accelerated, form a relatively stable dense layer in the material surface; but due to the flowing seawater also erosion the material surface,so that the outer layer of loose corrosion product film was washed away immediately aftergeneration. Therefore,90/10copper-nickel alloy in the process of erosion-corrosion mostlyshowed monolayer film. The impedance modulus decreased with the increasing flow velocityor sediment concentration. In erosion-corrosion process of clean seawater, the maximummodulus of Rfcan obtain in the impact angles of90°, the minimum modulus of Rfcan obtainin the impact angles of0°; In erosion-corrosion process of sediment seawater, the minimummodulus of Rfcan obtain in the impact angles of0°and90°. With the impact angle, the trendof Rfand Rtis opposites.(3)In the erosion-corrosion process of clean seawater, it found scratches on the surface.In the erosion-corrosion process of sediment seawater, it found impact craters on the surface,with the impact angle increases, the shape of impact craters gradually shift from thehorseshoe-shaped to dot.(4)The composition of the corrosion product film which formed under differentconditions mainly by oxides. On the corrosion product film of soaking condition found thepresence of NaCl.