The Study On Electrochemical Corrosion Behaviors Of Three Kinds Of Coating In The Simulated Soil Solution

Solvent-free epoxy coating of coal tar pitch has strong adhesion, high strength, water heat, corrosion resistance and other characteristics, are widely used in underwater and underground pipeline and metal structures. Because of the lack of systematic research for the protective effect of solvent-free coal tar epoxy coating, leading the accurate engineering and piping life assessment, but also to promote the limited of application for the coating. Therefore, the study of corrosion resistance and service life of the coating is particularly important.Based on the corrosion resistance for solvent-free epoxy coating of coal tar pitch (Universal), solvent-free epoxy coal tar pitch (for winter) and solvent-free epoxy coating of asphalt pitch in four soil simulation solution corrosion resistance. The results showed that the average open circuit potential of 200μm YS, MD, SYLQ coated immersed in coastal saline chlorine, saline-alkali soil, neutral meadow soil and acidic red loam simulation solution for 240 days is-0.40 V, -0.38V and -0.38V, the open circuit potential of Q235 is -0.65V; open circuit potential with thickening of the coating thickness and positive shift, indicating that the increase of the coating thickness increases the erosion shield blocking ability of the solution.Three kinds of coating immersed in simulated soil solution for 240 days, their AC impedance spectra show a single capacitive arc characteristic impedance value is greater than 8 × 108Ω·cm2, showed that the coating formed a effective shield coating for high resistance, low capacitance.the coating structure is compact, aggressive media does not penetrate into the coating / substrate interface.the coating plays a protective role for Q235 steel substrate.The breakpoint frequency of YS, MD, SYLQ coating has not exceeded 20Hz immersed in simulated soil solution for 240d,increasing penetration of the coating,The thicker the coating thickness, the smaller the coating breakpoint frequency value.The SEM images of three kinds of coatings section and surface after stripping immersed in simulated soil solution for 240d .The results shows section coat color lighter, but the coating has strong adhesion ,Q235 was not corrosion. XRD spectra of coatings surface after stripping include Fe and C phases,and not observed Fe3O4, Fe2O3, FeSO4, FeSO3, FeCl2 and other corrosion products phase.Using GM(1,1) established the coating corrosion life prediction formula The predicted life tine for YS coating immersed in the simulated coastal sodium chloride solution and acid soil solution is 781d and 418d,the coating from early age to middle time.