Electrodeposition And Radical Polymerization To Prepare Cross-linked Film On Aluminum Alloy Surface And Film Characterization

Aluminum alloy is extensively used in automobile and aerospace industries due to itsexcellent properties, such as low density, good ductility, easy modeling and high mechanicalintensity. However, aluminum alloy is subjected to corrosion and always suffers several typesof degradation, including pitting, exfoliation and intergranular corrosion. Therefore, it isnecessary to prepare protection film on its surface to improve the anticorrosion of thealuminum alloy.In this study, electrodeposition and radical polymerization technique were applied tofabricate triazinedithiol cross-linked film on aluminum alloy surface. The heterocyclicmonomer containing fluorine substituent of6-（N-allyl-1,1,2,2-tetrahydroperfluorodecyl）amino-1,3,5-triazine-2,4-dithiol monosodium （AF17N） was first electrodeposited onaluminum alloy surface by the two-step potentiostat technique. Then6-N,N-diallylamino-1,3,5-triazine-2,4-dithiol monosodium （DAN） was further polymerizedon the electrodeposition film（PAF） covered aluminum surface to fabricate the cross-linkedfilm（PAF/PDA） for ameliorating its anticorrosion efficiency. The best pretreatment beforecoating is plasma discharge treatment for20s. The optimum experimental conditions derivedfrom the orthogonal tests. The optimum conditions of AF17N electrodeposition by two-steppotentiostat technique are as following. The potential and time were1.6V and20s for thefirst step and then polymerized at7.0V for10s of the second step. The optimum conditionsof radical polymerization for DAN were: the concentration of DAN and K2S2O8were1.5mmol/L and0.12mmol/L, respectively. Assembling temperature and time were40℃and40min, respectively. And then be cured for10min at100℃. The assembly process carried outtwice.The film property under the optimum conditions was characterized by many methods.Wettability of samples was studied by contact angle. The film compactness was carried out bycyclic voltammograms in0.1%H₂SO₄solution. The corrosion inhibition property of the filmwas demonstrated in0.5mol/L NaCl aqueous solution by potentiodynamic polarization andsalty water test. Surface morphologies of aluminum before and after immersion tests wereobserved by scanning electron microscopy （SEM）. All results show that the corrosioninhibition efficiency of electrodeposition film and cross-linked film covered aluminum substrates increases markedly. Compared to electrodeposition film, the cross-linked film hasbetter effect for protecting aluminum alloy from corrosion.