Study On Corrosion Resistance Enhancment Of Graphene And Polyaniline Modificaed Magnesium-rich Coating

Nowadays, with the interiorization of lightweight and energy-saving notions, magnesium alloys ,which have low density, high rigidity and strength, have being used to substitute aluminium alloys, irons and many other alloys in many fields like aviation, automotive and aerospace fields.However, easy to corrode makes magnesium alloys' application limited.Brushing organic coating is one of useful methods of alloy protection.And the Mg-rich coating (MRC) could even protect alloys from corrosion by cathodic protection principle.As a new production, Mg-rich coating still has some defects. The magnesium particles inside the coating is more active than magnesium alloys. They will corrode immediately when conducted by electrolyte solution, which makes time of cathodic protection too short. So as to prolong the time of cathodic protection and corrosion resistance, we use doped polyaniline(PANI), graphene and graphene oxide to improve properties of Mg-rich coating. Using Machu test, EIS test, FTIR test and EIS test to study the change of Mg-rich coating, then we got these conclusions:(1) Relative to HCl, HF or camphorsulfonic acid doped polyaniline,sulfosalicylic acid doped polyaniline has the best effect of 50 wt%magnesium particles mixed Mg-rich coating improvement. When the addition of PANI is small(0.1 wt% or 0.5 wt% of magnesium particles),the corrosion resistance of the coating improved. While the addition is excessive(3 wt% or 5 wt%), the corrosion resistance of the coating would be reduced. It's reported that doped polyaniline could make a thin passivation film between alloy and coating, which provide an extra corrosion resistance protection for the alloys.(2) We add graphene to improve the Mg-rich coating with 50 wt%magnesium particles. When the substitution amount is small(m(Mg:Gr)=48:2), the cathodic protection and corrosion resistance of Mg-rich coating could be both improved obviously. The graphene could couduct the magnesium particles inside the coating and reduce the porosity. While the substitution amount is small or excessive the performance of the coating will both reduce, which would increase the porosity of the coating, and reduce the corrosion resistance.(3) We use graphene oxide to change the Mg-rich coating, which has high stability and moderate conductivity. As a result, we found that 1 wt%replacement of graphene oxide could prolong the corrosion resistance time. It's reported that oxygenated functional groups on the graphene oxide could connect to epoxides to increase the cross - linking density of the coating. It could increase the porosity of the coating accordingly, and reduce the corrosion resistance. But the cathodic protection time has not apparent change. If the substitution amount increased, the properties of coating will be worse.