Improvement Of Corrosion Resistance Of Waterborne Epoxy Coating By Ca Al-mbt-ldh

As a common metal,carbon steel is widely used in various fields,but it is easy to be corroded.Therefore,it is very important to strengthen the corrosion protection of carbon steel.As a common and efficient protection method,coating can effectively isolate the contact between metal and external corrosive environment and protect carbon steel.Improving the service life of coatings and developing coatings with self-healing properties are the focus of research.Layered bimetallic hydroxide（LDH）is a nano layered structure,which can effectively load corrosion inhibitors,and has a good application prospect in the field of anti-corrosion coatings.Nano layered LDH is applied to the anti-corrosion coating as filler,which not only fills the pores in the coating and improves its barrier performance,but also endows the coating with excellent self-healing performance through corrosion inhibitor intercalation.Therefore,this paper studies the preparation of calcium based LDH intercalated by corrosion inhibitor MBT and adds it as filler to the epoxy resin coating to improve the protective performance of the coating.In this paper,2-Mercaptobenzothiazole（MBT）intercalated CaAl layered double hydroxide（CaAl-MBT-LDH）was prepared by ion exchange method.It was added to waterborne epoxy resin as filler to improve its corrosion resistance.CaAl-MBT-LDH was characterized by XRD,FT-IR and SEM.The results showed that the inhibitor MBT was successfully inserted into the LDH layer,and the CaAl-MBT-LDH particles had a hexagonal structure.The corrosion protection effects of blank coating and CaAl-MBT-LDH modified coating were evaluated by salt spray test and immersion test.The results show that the scratch of the blank coating is seriously corroded after 170 hours of salt spray test,while when the addition amount of CaAl-MBT_{0.08 M}-LDH prepared was 2%（mass fraction of CaAl-MBT-LDH in epoxy resin）,the coating still had no serious corrosion traces.After soaking in 3.5%Na Cl solution for 13 days,the R_ctof the blank coating was only 1.62×10³Ω·cm²,the epoxy coating with 2%CaAl-MBT_0.08M-LDH was still as high as 2.76×10⁶Ω·cm²。The prepared CaAl-MBT-LDH powder was modified with silane（KH550）to improve its uniform dispersion in epoxy resin coating and further improve the corrosion resistance of the coating.The silane modified CaAl-MBT-LDH-KH550 was characterized by XRD,FT-IR and SEM.The FT-IR and SEM results showed that the silane coupling agent successfully modified CaAl-MBT-LDH.The XRD results showed that the modified CaAl-MBT-LDH-KH550 still had the characteristic structure of LDH（with the typical layered hexagonal structure of LDH）.SEM results show that there is a network covering on the surface of CaAl-MBT-LDH-KH550,which is consistent with the surface characteristics of particles modified by silane.The surfaces of CaAl-MBT-LDH modified epoxy resin coating and CaAl-MBT-LDH-KH550 modified epoxy resin coating were characterized by SEM.The results showed that the particles on the surface of the coating with CaAl-MBT-LDH-KH550 were more evenly dispersed.The corrosion resistance of epoxy resin coatings modified with CaAl-MBT-LDH and CaAl-MBT-LDH-KH550 was studied by salt spray test and immersion test.After 300 h of salt spray test,the scratch of CaAl-MBT-LDH modified coating is seriously corroded,while the scratch of CaAl-MBT-LDH-KH550 modified coating is not seriously corroded.When the addition amount of CaAl-MBT-LDH-KH550 is 2%,there is no obvious corrosion trace at the scratch,and the corrosion protection effect is the best.The charge transfer resistance(R_ct)of epoxy resin coating with 2%CaAl-MBT-LDH after soaking in 3.5%Na Cl solution for 13 days is only 2.76×10⁶Ω·cm²,while the R_ctof epoxy resin coating added with 2%CaAl-MBT-LDH-KH550 powder is still as high as8.96×10⁸Ω·cm²。The research shows that compared with the blank coating,the corrosion resistance of the coating is greatly improved after adding CaAl-MBT-LDH powder to the coating.While silane modification improves the dispersion performance of CaAl-MBT-LDH in the aqueous coating,it further improves the corrosion resistance of the coating.