Preparation And Properties Of Waterborne Epoxy Inner Coatings

At present,China's petroleum and natural gas resources was mainly transported through long-distance pipeline,and X80 will become the main trunk pipeline steel.The corrosive effect of the transport medium will reduce the thickness and the strength of the pipe,which results in serious consequences.The use of coating on its inner wall can greatly reduce the corrosion.Therefore,To study an environmentally friendly water-based anti-corrosion coating to keep X80 pipeline steel from corrosion is very practical significance.Using chemical method to modify E-44 epoxy resin,and the viscosity of the product is about 5000mPa.s.The product was well compatible with water and its viscosity was rapidly reduced after adding deionized water.Infrared spectroscopy analysis preliminary showed that the preparation of modified epoxy resin was successful.There was no stratification of the emulsion when a small amount of the product was centrifuged at 3000 r/min for 30 min.The cured product performance was best when the curing agent:modified epoxy resin was about 1:1.Through orthogonal experiments to study the impact of curing agent,coupling agent KH550,silica and zinc on the coating performance,getting the best recipe for the paint was curing agent 80%,coupling agent KH550 content of 5%,silica 10%,zinc powder 16%.After the immersion experiment,the coating performance was analyzed by means of electrochemical workstation,infrared spectrometer,thermogravimetric analyzer,scanning electron microscope and X-ray diffractometer.The results showed that the corrosion current density of the coating was the largest,1.341×10-5A/cm2,when the immersion temperature at 60? and the corrosion rate decreased when the immersion temperature increased from 60 ?to 70 ?.In different concentrations of the S2-medium,the corrosion rate was the largest when the S2-concentration was 2g/L and its self-corrosion current density was 4.837×10-6A/cm2 and the self-corrosion potential was-0.540 V.At different pressures,the corrosion rate increases with increasing pressure.When the pressure was increased to 5MPa,the corrosion potential was reduced to-0.568V,and the corrosion current density was increased to 7.128×10-5A cm2.It was also found that the coating functional group stability and thermal stability were good and the products ZnO,FeS and so on had certain protective effect on the coating.The effect of graphene on the corrosion resistance of the coating was further studied and it was found that triton modified graphene was evenly distributed in the coating.The distribution of salicylic acid modified graphene in the coating was chaotic,and it was also found that graphene was deposited on the coating surface.The result showed that the dispersibility of salicylic acid modified graphene in waterborne epoxy coating was not good and the modified effect of triton on graphene was better than that of salicylic acid.After immersing in 3.5%NaCl solution for 10 days,the triton modified graphene coating surface was bubbled,but no holes were found.While the salicylic acid modified graphene coating surface appeared small holes with size of about 4?m.This showed that the modified Triton-modified graphene coating had better corrosion resistance during soaking experiments.It was because the two-dimensional lamellar structure of graphene not only had the physical barrier effect in the coating,but also had the effect of inhibiting the diffusion of dissolved oxygen and corrosive medium in the coating.