The Anticorrosive Performances And Mechanism Investigation Of Zinc-rich Coating With Graphene Nanoplates Modified

Owing to the excellent physical and chemical properties of graphene,thus compositing graphene with organic coatings to enhance its original performance has attracted lots of attentions in the anticorrosive field.In this thesis,the zinc-rich epoxy coatings(ZRE)were modified by graphene nanosheets(Gnps)to prepare Gnps/ZRE composite coatings with well-dispersed Gnps.The Raman spectroscopy,scanning electron microscopy,salt spray test and electrochemical test,were employed to invesitigate the quantitative effect of Gnps(0.5wt.%)on anticorrosion properties of ZRE with different zinc content(10,40,70 wt.%)and anti-corrosion mechanism.To explore the effects of different Gnps additions(0,0.3,0.5,1.0,1.5 wt.%)on the anticorrosive behaviors of ZRE with 40 wt.% zinc content(Gnps/40ZRE)and its anti-corrosion mechanism.The corrosion resistance around simulated defects of the 40-ZRE and 0.5Gnps-40 ZRE and its corrosion mechanism were comparatively studied.The main progress of this thiese are as follows:(1)Cathodic protection time increment((35)Tx)and shielding performance enhancement coefficiency(?x)were self-defined,to quantitatively evaluate the effect of Gnps on the cathodic protection duration and the improvement of shielding performance of ZRE coatings with different zinc contents.Comparing with ZRE coating,the cathodic protection durantion and shielding effects of 0.5Gnps/ZRE coating for metal substrate were significantly extended and improved.(2)Whether ZRE was loaded with Gnps or not,three different stages could be proposed during the whole immersion: water infiltration,zinc activation and zinc passivation,and the anticorrosive models of different stages were established.(3)For the Gnps/40 ZRE composite coating,while Gnps addition was <0.5wt.%,the physical shielding performance of the Gnps/40 ZRE composite coating was mainly improved.While the Gnps addition was 0.5~1.0wt.%,the physical shielding performance and cathodic protection effect of the Gnps/40 ZRE composite coating could be both significantly improved.While Gnps addition was >1.0wt.%,no obvious improvement for both physical shielding performance and cathodic protection effect could be seen.Therefore,the optimal addition amount of Gnps for 40-ZRE was 0.5~1.0wt.%.(4)The addition of Gnps could enhance the anti-delamination ability of Gnp/40 ZRE composite coating around the defect.There were two different stages for both 0.5Gnp-40 ZRE and 40-ZRE coatings during the immersion.In the early stage,the metal matrix of the defect was under cathodic protection,the delamination of the coating had not yet occurred.At the late stage,the anodic dissolution of the metal matrix took place,which resulted in disbonding of the coating.