Preparation Of New Composite Coating And Its Corrosion Resistance Study

The high temperature corrosion of the key components of biomass or waste incinerator,such as water wall and superheater tube,is a major challenge faced by countries all over the world.At present,the coating/substrate system is considered to be a good technical solution.When the single-layer coating is used in a complex corrosion environment,pipeline failure,pipeline leakage,accidental shutdown and other phenomena usually occur,and the anti-corrosion performance is not satisfactory.In this paper,a new coating preparation system was used to prepare the composite coating,the anti-corrosion performance and corrosion mechanism of the composite coating under different working conditions were studied,and the industrial application experiments were carried out,and the preparation process of the coating was optimized according to the research results.in order to improve the service life of municipal solid waste incinerator boiler tube.The preparation process of the composite coating is mainly divided into three parts:first,the bottom layer is prepared by flame spraying,and then the bottom layer is remelted by high frequency induction remelting,finally,the ceramic coating is prepared by supersonic plasma spraying in the remelting process,and the coating covered by ash is studied by high temperature flue gas corrosion experiment and hot corrosion experiment.After the corrosion experiment,the corrosion products of the coating were analyzed by X-ray diffractometer(XRD),the microstructure and element distribution of the test samples were observed and analyzed by scanning electron microscope(SEM)and energy dispersive spectrometer(EDS),and the corrosion resistance of the coating was tested by weight gain method.The results show that the anticorrosion performance of the composite coating is better than that of the single layer coating,and the corrosion of the composite coating in high temperature flue gas environment is mainly electrochemical active oxidation combined corrosion mechanism.however,the corrosion in the hot corrosion environment is mainly galvanic corrosion.3 months of industrial application experiments show that the composite coating can be applied to the actual garbage power plant boiler tube protection,and the protective performance is good.Finally,some suggestions are put forward for the preparation of the coating:for the single-layer coating,the corrosion potential is lower than that of the substrate,the compactness of the coating should be improved and the coating defects should be reduced as much as possible;for the composite coating,the corrosion potential of the bottom layer should be between the top layer and the substrate,and the corrosion potential of the top layer is lower than that of the bottom layer,and the compactness of the bottom layer should be improved.