## 1 Introduction  
Over past few decades, many effective strategies such as adding corrosion inhibitors, cathodic protection, surface treatment and coating technology have been widely developed to prevent corrosion in the marine industry and ensure the structural integrity of the alloy [1; 2; 3]. Among them, coating technology is the most widely used anti-corrosive approach, not only because it has a simple process, but also the low porosity generated from the coating can effectively retard corrosion [4; 5]. Epoxy resin (EP) has good mechanical properties, considerable adhesion and stable chemical properties. However, corrosive media such as H\({}_{2}\)O, O\({}_{2}\) and Cl\({}^{-}\) will inevitably penetrate into its coating layers and reach the substrate surface through holes and defects formed by solvent volatilization during long-term immersion [6]. One of the most effective ways to solve this problem is to dope nanomaterials to epoxy resins, where nanomaterials can effectively prevent those corrosive medium from entering the coating layers through the filling of micropores. Many efforts have been denoted to introduce nanomaterials such as clay, carbon nanotubes, TiO\({}_{2}\), SiO\({}_{2}\) and graphene into epoxy coatings to improve their anti-corrosion properties [7; 8; 9; 10; 11; 12]. Among these materials, graphene oxide (GO) has a the characteristics of high specific surface area, good mechanical strength and physical barrier effect, which can significantly prolong the diffusion path of corrosive medium [13; 14; 15; 16; 17; 18]. Polyaniline (PANI) is a well-known conductive polymer, which has light-weight, non-toxic, low-cost, good electrochemical and reversible redox characteristics [19; 20; 21]. Many reports have confirmed that PANI coating with a certain thickness has the effect on physical shielding and the special redox performance, which can promote the formation of a protective oxide film on the surface of metal and passivates the metal matrix [22; 23]. [PERSON] et al. [24] found that PANI as an additive can alleviate the corrosion of metals. [PERSON] [25] and [PERSON] [26] added PANI to epoxy resin to form a good nanocomposite, where PANI can generate electrons to form a passivation film and form a chemical shielding layer [27]. Although GO-PANI nanocomposite can improve its barrier properties for oxygen and water with the covalent grafting of PANI and GO, the aggregation of nanocomposites will produce undesired pores and defects, which will in turn accelerate the penetration rate of corrosive medium and eventually lead to serious corrosion. The amino and hydroxyl functional groups of dopamine (DA) make it easy to be functionalized and cross-linked with other materials, resulting in the improvement of the dispersion ability and the compatibility between fillers and resins [28; 29; 30; 31; 32; 33]. Benefitting from good compactness, anchorage and uniformity, the polydopamine (PDA) coating is a promising candidate filler for an anti-corrosion coating [34; 35]. [PERSON] et al. [36] found that DA can enhance the compatibility and adhesion of graphene with epoxy resins and avoided galvanic corrosion. [PERSON] et al. [37] found that dopamine-functionalized graphene oxide (DA-GO) formed a protective layer to prevent carbon steel from corrosion. Due to the hydrogen bond between GO and PDA as well as the electrostatic interaction between -COO\({}^{-}\) in GO and -NH\({}^{3+}\) in PDA, we propose that the grafting of dopamine on GO will help promote the compatibility of GO-PANI nanosheet in epoxy resin, thereby improving the corrosion inhibition efficiency of the coating. [PERSON] et al. [38] prepared a novel nanocomposite Ag-Pd-PDA/RGO to reduce the consumption of palladium, improve the catalytic activity of Pd, and have a synergistic effect. [PERSON] et al. [39] confirmed that both barrier and inhibitory action of epoxy coating were significantly enhanced in the presence of GOQD-PANI. The fine GOQD-PANI well dispersed in the epoxy matrix, filled the pores and defects and blocked the diffusion pathways.