| With the rapid development of economy,the demand for energy is increasing,especially oil.In the process of petroleum processing,the corrosion of equipment and equipment is becoming more and more serious.Accidents caused by corrosion of equipment and installations happen occasionally.Scientific and rational precautions must be taken to protect equipment and devices.Sewage storage tank is a special equipment in petrochemical,oilfield,coal chemical industry and other industries.The sewage composition is complex and often causes the corrosion of the storage tank.The stress corrosion cracking in the weld seam causes the leakage of the sewage.The pollution environment endangers the safety production and the coating is often used for anticorrosion.Special anticorrosive coatings must be selected for the particularity of the sewage medium.In this study,the Q235 steel,petrochemical actual sulfur-containing sewage,artificial sulfur-containing sewage formulated according to the composition of wastewater,and four anti-corrosion coating systems(Phenolic epoxy glass scale anticorrosion coating,Epoxy glass flake anticorrosive coating A,Epoxy glass flake anticorrosive coating B,Epoxy nano modified anticorrosive coating)were used as research object.The corrosion test of Q235 steel and four kinds of anti-corrosion coating systems in the actual and artificial sulfur-containing sewage at 60? were carried out for 4 cycles(30d,60 d,90d and 120d).The corrosion morphology analysis,corrosion product analysis and corrosion kinetics analysis,combined with electrochemical technology(polarization curve,AC impedance spectroscopy)were used to comprehensive analysis the corrosion behavior and corrosion effects of Q235 steel in two media,through the conventional anti-corrosion coating system.Performance tests,corrosion morphology analysis and electrochemical tests were performed to compare the corrosion resistance of the four anti-corrosion coating systems in the two media.Through the routine performance testing,corrosion morphology analysis and electrochemical testing of the four anti-corrosion coating systems,the anti-corrosion performance of the four anti-corrosion coating systems in the two media was compared.The results of the research are shown as follow:(1)The corrosion degrees of Q235 steel soaked in the actual and artificial sulfur-containing sewage for 120 days are different,and the corrosion in different areas(full-immersion area,atmospheric area)is also different.In the Guangzhou petrochemical sulfur-containing sewage,there was no obvious corrosion pit on the surface of Q235 steel after immersion corrosion in the fully immersed zone for 60 days,and rust spots appeared on the surface of Q235 steel after 90 days.The corrosion of the Q235 steel in the atmospheric zone is more serious than that in the fully immersed zone,rust spots begin to appear on the surface of the Q235 steel after 30 days of the test,and more corrosion appeared on the surface after 90 days.The corrosion rate of Q235 steel in the atmospheric zone is greater than that in the fully immersion zone.Within 4 cycles,the maximum corrosion rate of the full immersion zone is 23.4 ?m/a,and the maximum corrosion rate of the atmospheric zone is 33.5 ?m/a.The corrosiveness of artificial sulfur-containing sewage is greater than that of petrochemical sulfur-containing sewage.The maximum corrosion rate in the full-immersion zone is 129 ?m/a in four cycles,and the maximum corrosion rate in the atmosphere is 386 ?m/a.The corrosion rate in the atmosphere is greater than that in the full immersion zone.The atmospheric corrosion products are mainly Fe S,Fe2O3,Fe3O4 and ?-Fe OOH,while the corrosion products in the complete dip zone are mainly Fe S and Fe3O4.(2)The temperature has a significant effect on the corrosion of Q235 steel in the two media.As the temperature increases,the corrosion current density increases and the corrosion rate increases.(3)In the content range of sulphur containing sewage,the effect of ion concentration on corrosion of Q235 steel is manifested as follows: The increase of the concentrations of S2-,Cl-and(NH4)2SO4 solution can promote the corrosion of Q235 steel.In sulfur-containing aqueous solutions,the increase of SO42-ion concentration can also promote the corrosion of carbon steel.(4)The galvanic corrosion current was measured with an ACM couple electrode to investigate the corrosivity in the two corrosive solution media and under the thin liquid film.The results showed that the corrosion current under the liquid film is greater than the corrosion current of the sulfur-containing sewage during the drying process by adding artificial sewage medium to the ACM probe.The corrosion current of the two solutions in the drying process is higher than that in the full leaching process.The results show that the corrosion of the atmospheric area is greater than that of the whole immersion zone under the relatively closed hot and humid environment,and the result is consistent with the result of the corrosion weight loss.(5)Through the routine performance and corrosion resistance tests of the four kinds of anti-corrosion coating systems,it was found that the four anti-corrosion coating systems have excellent performance,and the alkali resistance of the epoxy glass anticorrosive coatings A and B is poor.Corrosion resistance of anti-corrosion coating in Guangzhou Petrochemical's sulfur-containing wastewater and artificial wastewater was analyzed by immersion corrosion test and electrochemical impedance spectroscopy(EIS)technique.The results show that artificial sulfur-containing wastewater can be used to study the anti-sewage performance of the coating system.The phenolic epoxy glass type glass scale anticorrosion coating has the best corrosion resistance in the four anticorrosive coating systems.The other three kinds of coating systems are not suitable for anticorrosion of storage tanks. |
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