Preparation Of Co-Doped PANI And Their Effects On Anti-Corrosion Performance Of Epoxy Resin Coatings

The economy loss,safety accidence,energy waste and environment pollution caused by metal corrasion have seriously hampered the productivity and technology advancements.Coating the metal surface is considered as one of the most effective methods to prevent corrosion.As conductive polymers,the doped polyaniline（PANI）and its derivatives could decrease the corrasion rate of stainless steel,low carbon steel,copper,aluminum and other metals,thus attracting extensive attention.This paper concludes three parts:Firstly,HCl or H₃PO₄ were used as protonic acid,Sodium dodecylbenzene sulfona te（SDBS）as both emulsifier and co-dopant to synthesize a bundle like co-doped PANI of large molecular chain by low temperature slow emulsion polymerization.After being characterized by FT-IR,SEM,XRD and other methods,these materials were further added to the epoxy resin coating based on low carbon steel.Then,the anti-corrasion performance of the composite coating was investigated by EIS test and immersion test.The results revealed that the PANI co-doped by hydrochloric acid and dodecylbenzene sulfonic acid（（HCl+DBSA）-PANI）facilita tes the improvement of anti-corrasion performance for epoxy resin,and the main corrosion resistance mechanism is shielding effect and passivation effect.The above composite coating was optimized to study the influence of epoxy diluent type,epoxy additive type and co-doped PANI amount on the anti-corrasion performance of composite coating.We found the composite coating owns the excel ent performance when adopting phenyl glycidyl ether（PGE）as the epoxy diluent,de-foaming agent or leveling agent as epoxy agent and adding 1.0 wt.%of co-doped PANI.The initial impedance of the coating was even up to 10⁸Ω·cm² after immersed for 150 days by EIS test,and the anti-corrosion mechanism is mainly shielding effect which increased labyrinth effect of coating.Next,three kinds of organic hybrid acids including phenyl phosphoric acid（PPOA）,phosphor molybdic acid（PMA）and beta naphthalene sulfonic acid（β-NSC）were added into DBSA to prepare co-doped PANI,which was further employed to compare the anti-corrosio n performance with the separately doped PANI in epoxy coating.The results demonstrate that the structure of PANI co-doped withβ-NSC is more compact and uniform.Also,the corrosion rate of low carbon steel could be significantly reduced by adding epoxy resin coating.