Preparation Of Polyaniline/Graphene Composites And Study On The Corrosion Resistance Of Its Epoxy Coatings

Corrosion of metals is bound up with people's lives,therefore,effective measures must be taken to protect metals from corrosion.Anti-corrosion coating is one of the most common methods to prevent corrosion of metals,meanwhile,epoxy-based coating is the most commonly used coating.However,traditional epoxy resin coating is difficult to reach the requirements of heavy anti-corrosion,which needs to be modified by adding fillers to enchance the performance.Polyaniline(PANI)has unique anti-corrosion properties and has received widely attention in the field of heavy anti-corrosion.However polyaniline is insoluble and non-melting,which makes it difficult to process.When PANI is used alone as an anti-corrosion paint additive,it has a single function and limits the further improvement of its anti-corrosion coating properties.Graphene also has a unique anti-corrosion property when it is used as a functional filler.However,the cost of graphene preparation is expensive.When it is used as an anti-corrosion paint additive,it will greatly increase the cost of the coating.Polyaniline and graphene have different anticorrosion mechanism.Preparation of polyaniline/graphene composites can combine the anti-corrosion characteristics of the two materials with superior anti-corrosion properties.It also can effectively reduce the cost while improving corrosion resistance.In this paper,polyaniline/graphene composites have been synthesized through two different ways and were added to the epoxy resin to prepare an anti-corrosion coating.The basic properties and anti-corrosion performance of the coating have tested.The specific research contents are as follows:1.Firstly,graphene oxide(GO)was synthesized by the improved Hummers method from flake graphite,p-phenylenediamine was used to modify GO to obtain GON.Then GO was grafted with polyaniline to get GON-An(1:2).In the meantime,GON-An(1:5)and GON-An(1:10)were prepared as control groups by changing the grafting ratio of aniline.The structures,morphologies and elements of GON and GON-An(1:2)were characterized by FT-IR,XRD,Raman,SEM,EDS,TEM and XPS.Then,epoxy resin based coating(GON-An02E)with 1 wt%addition amount of GON-An(1:2)was prepared,and multiple sets of controlled experiments were also prepared,i.e.EP,GOE,GONE,GON-An05E,and GON-An1OE.The properties of those coatings were also explored.The research shows:GON and GON-An02 were synthesized successfully,and GON-An02E has good coating adhesion(grade 2)and coating hardness(4H).Bode shows that the adding of GON-An(1:2)can improve the corrosion resistance of the coating,and it has the slowest corrosion rate in the soaking process,the impedance still reached 4·109?cm2 after soaking for 35 days.The scanning electron microscope of the coating section shows that GON-An(1:2)had good dispersion in the coating.The scratched coatings after being immersion in NaCI water shows that GON-An02E still maintain a good morphology.Tafel polarization curve shows that the undamaged zone of GON-An02E has high corrosion potential-0.25V,and the corrosion current is only 4.119· 10-11 A/cm2,which shows the best anti-corrosion performance.2.The expandable graphite was thermal treated to obtain expanded graphite.Then the polyaniline/graphene composite An/G 100 was prepared by in-situ polymerization of aniline intercalating graphite.The ratio of aniline was changed at the same time to prepare An/G 10 and PANI,and mixed the polyaniline and expanded graphite to prepare An+G10O.The morphology and structure of An/G 100 were characterized by FT-IR,XRD,SEM,and TEM.Then a series of coatings were prepared with the addition of An/G100 added in an amount of 1-5 wt.%.At the same time,the coating of EP,An/G10 and PANI with addition amount of lwt%-5wt%,and An+G100 with addition amount of 1wt%were prepared as control groups.The properties of those coatings were also and explored.The research shows:An/G100 was synthesized successfully.With the increase of the proportion of filler,the adhesion of the coating will decrease slightly from grade 2 to grade 3.An/G100 coating show good coating adhesion(Grade 2)and coating hardness(4H)at the low add ratio.Bode results show that each coating with An/G100 filler exhibits better corrosion resistance than PANI and An/G10 coatings after 35 days of soaking.When the proportion of fillers increase,the anti-corrosion ability of An/G100 coating increase first and then decrease.Among them,the resistance values of An/G100-2 and An/G100-3 could still reach 1·1010 ?cm2 after immersion for 35 days,which has the highest value of the impedance of all formulations after immersion for 35 days.The scanning electron microscope of the coating section showed that the An/G 100-2 has more ladder shapes and rougher section.The scratched coatings after being immersion in NaC1 water shows that An/G100O coating still maintain a good morphology in every proportion.Tafel polarization curve shows that the undamaged zone of An/G 100-2 has high corrosion potential-0.16V,and the corrosion current is only 1.514· 10-11A/cm2,which shows the best anti-corrosion performance.