| The recycling of heat from flue gas has significantly economic and social benefits. However, the problem of fouling and corrosion in the heat exchanger is a major threat and potential pitfalls to the normal operation. Now anti-corrosion coating is an important way to solve the corrosion and scaling problems of this kind of heat exchanger. The common feature of the surface modification with organic polymer is that the thermal conductivity is much lower than that of conventional metal surface, which restricts the application of anti-corrosion coatings.In this paper, the nano-Cr2O3 particles were added into the Fluorocarbon(PFA) coating with the blending technique. The surface morphologies and structures of the coatings were characterized by FT-IR, Metallurgical Microscope, TGA, EPMA, contact angle measurement. The coating thermal conductivity of the coatings was tested by the Instantaneous index method and the corrosion resistance by corrosion experiments. The results showed that the microporous of the organic PFA coatings were filled by the nano-Cr2O3 particles and the thermal conductivity of the modified coatings were improved siginificantly. When the mass content of nano-Cr2O3 was 4%, the coating thermal conductivity was up to 0.396W/mK, with 30%increased of the thermal conductivity. The coating thermal conductivity improved with the mass content incressing. The average corrosion rate of the stable corrosion phase of the 4% nano-PFA coatings was about 30%less than that of the PFA coatings alone. Potentiodynamically polarization curves and electrochemical impedance spectroscopy(EIS) were condueted to evaluate the coating corrosion performance. The excellent corrosion resistance of the nano-coating was demonstrated when the dimensional passive current density was 0.5 orders of lower than PFA coating and the the corrosion potential was 400mV higher. EIS tests also showed that the addition of nanoparticles improved the corrosion resistance of the coating. But the content of the nano-Cr2O3 increased to 8%, the addition of nanoparticles could not improve the corrosion resistance of the coating. With addition of 11%, the dimensional passive current density of the coating decreased rapidly,, and accordingly. and accordingly the corrosionresistance decreased sinificantly.In order to prevent agglomeration of nanoparticles and improve the compatibility with the organic coating, the nanoparticles was modified with amino-silane coupling agent (AS). The optimal modification conditions was 0.8%of the AS. operating at 40℃, for 1h by the orthogonal experiments. The thermal conductivity of the coating has little difference between the before and after modified Cr2O3 nanopaticles; but the corrosion resistance of the coatings was influenced by the addition different contents. Polarization curves showed that the corrosion resistance of the nanocomposite coatings was not incressed when the content of nano particles was below 4%. When the nano-particles content increased, the protective effect of modified nano-particles increased significantly to the corrosion resisitance. With the content of 11%, the corrosion potential increased 100mV and the dimensional passive current density reduced 0.5 orders, similar with results of content of 4%.The Influencing mechanism of nanoparticles to the corrosion resistance of the PFA coatings was analyzed. In the early immersion, the coating was repaired by the nano-particles. With immersion continued, the Warburg impedance characteristics of the EIS showed that the addition of nanoparticles extended the way of the penetration of electrolyte solution and improved the shielding effect to the corrosion medium of the coatings.The resistance to water permeability of organic coatings is an important indicator of the protective properties of organic coatings. The diffusion coefficient of the coating for water is 2.2×10-10cm/s and the volume fraction of the saturated absorption capacity of coatings was 26.2%from the capacitor analysis with a high frequency.
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