Study On Properties Of Platinum Clad Impressed Current Andodes In The Simulate Deep Seawater

Deep-sea area (more than 300m), occupying 88% of the earth, has abundant oil-gas and mineral resources. Entering 21th century, the international competition of marine safeguard rights, developing and possessing marine resources as the core, has been more and more drastic. With the development of our comprehensive national power, our country must participate in competition of deep-sea domain and breakthrough the second island chain in economic and military, so the competition becomes our inevitable choice adapting to global development and deep ocean technology has become more and more important. The ocean engineering and weapon equipments are suffering corrosion damage in bad ocean environment during their service. Coating protection and cathodic protection are effective measures to control corrosion. Compared with ocean surface, the relative parameters of corrosion change greatly, raising new higher requirements for measures of corrosion control in deep ocean. Auxiliary anode is the key part of impressed current cathodic protection system.Platinum composite anodes, a material of insoluble auxiliary anode, because of its long service life, large load current density and small size, has been widely used in vessel, wharf projects and so on. The electrochemical properties of the Platinum composite anodes are excellent in general environment, but it changes inevitably with the increase of the seawater deepness, as a result effect its operational performance. The purpose of this study is to research the effect of temperature and dissolved oxygen concentration on platinum composite anodes.In this paper, platinum composite anodes were prepared by metallurgical drawing. The micro-morphology, element distribution, phase structure of the anodes and platinum layer thickness were studied by scanning electron microscope(SEM), energy spectrometer(EDS), X-ray diffraction(XRD), and metallographic microscope (OM). The corrosion resistance of the anodes in different solution medium was researched by potentiodynamic polarization. The electrochemical properties of Pt/Nb,Pt/Ta composite anodes and the difference between them were studied by potentiodynamic polarization, cyclic voltammetry, electrochemical impedance spectroscopy applied dc potential, test at a constant current density and matrix breakdown voltage in seawater with different temperature and dissolved oxygen concentration;The dissolution and failure of anodes was studied by accelerated electrolysis testing in seawater.The results showed that the surface of platinum composite anodes had high relative density and the average thickness of platinum layer which bonded with matrix metalllurgically was about 20μm. The surface had micro-attack defects and was not pure platinum but Fe3PtC compounds. The anodes had excellent resistance corrosion and good electrochemical properties in different solution medium; the effect of temperature was relative obvious to the electrochemical catalytic activity of anodes; Although the dissolved oxygen concentration had significant promotive function on anodes'secondary passivity, it became not obvious at relatively high potential; electrochemical properties of Pt/Ta composite anode was better than Pt/Nb composite anode, and could have better performance under worse condition.It was also found that Pt/Ta composite anode formed advanced oxides of platinum such as PtO2,PtO3,which could easily dissolute at high potential in seawater. With comprehensive actions of surface micro-cracks and gas percussion, the oxides had high consumption rate; the main failure type of platinum composite anodes was that platinum layer could dissolute and shed storey-by-storey.