Study Of The Characteristics And The Anticorrosion Mechanisms Of The Self-healing Coatings Based On Corrosion Inbibitor Loaded Natural Polysaccharide Microspheres

In recent years,researchers have proposed to add the host carriers encapsulated or loaded with corrosion inhibitors into the coatings to obtain self-healing ability and achieve an excellent anti-corrosion performance.We reported the fabrication of ecofriendly natural polysaccharide(chitosan,Sodium alginate)microspheres loaded with corrosion inhibitor(Sodium phytate,Sodium tartrate)for the first time,and applied them in self-healing water-based polyacrylate coatings.The optional experimental conditions were obtained by means of orthogonal experiments.The release kinetics of corrosion inhibitor from the microspheres under pH =3,7,9 was indirectly studied through examining the efficiency of the corrosion inhibitor by electrochemical measurements.The self-healing properties of the coated copper samples with water-based coating doped with corrosion inhibitor loaded microspheres were also evaluated by electrochemical measurements,and the anticorrosin performance of the modified coatings was examined by seawater immersion tests.The optional experimental conditions for preparing chitosan microspheres was: 1:20 of water/oil ratio,3:1 of the mass ratio of vanilline/chitosan,pH =9 of the mixed solution,under which condition the microspheres were in perfect spheres with uniform size ranging from 20 to 30 ?m.For preparing Sodium alginate microspheres,the optional experimental conditions was: 1:20 of water/oil ratio,2:100 of emulsifier/oil ratio,4:1 of mole ratio of acetic acid/Calcium carbonate.The size of the Sodium alginate microspheres prepared under this condition was about 20 ?m.The corrosion inhibitor Sodium phytate and Sodium tartrate were successfully encapsulated in the microspheres.The load rate were respectively 25.79 wt.% and 35.00 wt.% in chitosan microspheres,as well as in Sodium alginate microspheres the load rate were 29.85 wt.% and 30.65 wt.% respectively.The results of EIS measurements showed that the release rate of the both corrosion inhibitors in chitosan microspheres were fastest at the condition of pH= 9 followed by the release rate at pH= 7 and pH= 3,while in Sodium alginate microspheres the release rate of the both corrosion inhibitor accorded with pH= 9> pH= 3> p H= 7.K-P model was the best fit model to estimate the release kinetics of the both corrosion inhibitors.When the chitosan and Sodium alginate microspheres loaded with corrosion inhibitors were respectively added into the water-based coating,a significant increase of charge transfer resistance could be obtained,indicating the self-healing capabilities of the modified coating.The seawater immersion test further revealed that the water-based coating modified with these four kinds corrosion inhibitor loaded microspheres could restrain corrosion process around defected areas,as a result of the release of corrosion inhibitors.Therefore,the eco-friendly chitosan and Sodium alginate microspheres could control the release of corrosion inhibitors Sodium phytate and Sodium tartrate under different pH conditions.According to the experiment results,the modified coating not only exhibited excellent self-healing properties but also showed high anti-corrosion performance.It is anticipated that this study can open a new way to design a new strategy of preparing efficient and eco-friendly anticorrosion smart coatings.