Study On Anticorrosive Coating On Carbon Steel Surface In Simulated Offshore Atmospheric Environment

Carbon steel is widely used in marine environment due to its high strength and low cost,but its corrosion resistance is poor.In order to improve the corrosion resistance of carbon steel,coating epoxy resin corrosion resistant coating on the surface is the most widely used anti-corrosion measure.At present,waterborne epoxy resin coatings are favored by many researchers due to their hydrophilicity and environmental protection.Hydrophilic groups in silicone can improve the hydrophilicity of the resin,acrylic acid can improve the weather resistance and chemical resistance of the resin.Therefore,it is necessary to use silicone and acrylic acid to modify epoxy resin to improve corrosion resistance.In this paper,the effects of different resins on the properties of the coating were studied by different test methods to investigate the corrosion resistance of the coating before and after modification.Firstly,two kinds of corrosion resistant coatings were prepared with epoxy resin E-51 and E-44 as the base materials.The preparation process was optimized by single factor and orthogonal test and the optimal formula was determined.Secondly,in order to further improve the overall performance of epoxy resin coatings,E-44 as raw material,the introduction of more hydrophilic and corrosion resistance of silicone and acrylic acid mixed monomer,modified epoxy resin by core-shell emulsion polymerization,and its structure was characterized by infrared analysis.Then,the corrosion-resistant coating was prepared with the modified resin as the base material.The preparation process was optimized by response surface method,and various performance tests were carried out.Finally,the performance of the three coatings was tested and compared by electrochemical test,surface morphology and salt spray test.The main work of this paper is as follows:（1）Two kinds of corrosion resistant coatings were prepared with epoxy resin E-51 and E-44 as base materials.The corrosion current densities of epoxy resin E-51 and E-44 were 2.17×10^-7 A/cm² and 9.48×10^-7 A/cm²,respectively.The other corrosion resistance and basic properties of the coatings can meet the national standards.（2）The modification of epoxy resin E-44 by silicone and acrylic acid was studied by core-shell emulsion polymerization,and the optimal formula was obtained.The performance tests showed that the emulsion was milky white and blue,the solid content was 45.28%,the conversion rate was 98.33%,the grafting rate was 78.62%,the epoxy value was 0.36 mol/100g,and the water absorption was 4.08%.It has good Ca²⁺stability,dilution stability and storage stability.Then,the modified resin was used as the base material to prepare the corrosion-resistant coating.The data of the modified coating were analyzed by the response surface method,and the optimal formula was obtained:The pigment-to-binder ratio was 3.3,the content ratio of zinc phosphate to aluminum tripolyphosphate was 1.3,and the content of mica powder was 6.7%.The modified coating under the optimal formula was tested by acid and alkali resistance,salt water resistance,adhesion and other performance tests and electrochemical test characterization.It was concluded that the acid resistance of the prepared coating reached 15 d,the alkali resistance reached 31 d,the salt water resistance reached 30 d,the adhesion was 0 grade,and the corrosion current density was 4.38×10^-8 A/cm².The coating can meet the national standards.（3）The microstructure of different coatings was analyzed by scanning electron microscope（SEM）.Compared with the two coatings before modification,the pores on the surface of the modified coating are obviously reduced and the compactness of the coating is higher.Salt spray test showed that after 720 h,the modified coating did not appear bubbling and wrinkling.The polarization curve test results show that the corrosion current densities of epoxy resin E-51 and E-44 coatings are 2.17×10^-7 A/cm² and 9.48×10^-7 A/cm²,respectively.The corrosion current density of the modified coating decreases to 4.38×10^-8 A/cm².It can be seen that the modified coating can significantly improve the corrosion resistance of carbon steel.