COMPLEX PROTECTION OF STEEL FROM CORROSION BYALLOYED BORIDE AND SILICIDE COATINGS WITHCORROSION INHIBITORS

摘要

Novel high affectivity methods of protection of carbon steel by using therncomplex diffusion alloyed by transition metals boride and silicide coatings withrncorrosion inhibitors have been developed in the National Technical University ofrnUkraine "Kiev Polytechnic Institute". Phase, chemical composition, microhardness,rnmicrobrittleness, microporosity, corrosion and cavitation resistance in different mediarnhave been established.rnIt has been established that boride phases with dissolved metals (0.2….0.8 %rnmass of Ti, V, Cr, Mn, Co, Ni, Nb, Mo, W) are formed due to complex saturation ofrnboron and transition metals. Phase composition of silicide coatings alloyed by transitionrnmetal depends on carbon content in treatment steel. A-Solid solution of silicon andrntransition metal (for example, chromium) in iron is formed by complex saturation ofrnlow carbon steels. Besides a-solid solution, carbides of alloying elements are formed onrnthe high carbon steel surfaces.rnIt has been established that the main factors influencing on corrosion resistancernof studied coatings are following: aggressive medium; stability of metal to chemicalrninteraction with solution components determined by bonds of intercalation phase inrncrystal lattice; microporosity of diffusion layers; durability of their bonds with metalrnsurface. Boride and silicide coatings alloyed by chromium are the most corrosionrnresistance.rnIt has been established that the influence of boride and silicide coatings alloyedrnby chromium on electrochemical behavior of steel in acid solutions is different..Studiedrntypes of coatings influence on the cathode reaction of steel corrosion in H2S04 andrnHN03 solutions low. Boride coatings inhibit its dilution in active area but silicide one -rnin area of passivation.rnIt has been shown that the increase of protecting properties of diffusion coatingsrncan be achieved by infusion of corrosion inhibitors into aggressive medium. Using therncorrosion inhibitors of adsorption types is the most effective for boride coatings; thernaction of adsorption inhibitors and the inhibitors-passivator is the same for siliciderncoatings. The mechanism of protecting action of inhibitors have been studied. Thernblocking and energetic effects in corrosion inhibition of investigated compounds havernbeen found. Recommendations for practical use of complex steel protection in differentrnaggressive media have been proposed.