Walnut shell extract as sustainable, eco-friendly and cost-effective green corrosion inhibitor for fabrication of active protective nanocomposite coating based on mesoporous carbon hollow nanospheres

This paper presents anticorrosion performance of epoxy resin containing walnut extract as green inhibitor doped in mesoporous carbon hollow nanospheres (MCHNSs). In the first step, mesoporous silica hard templating method was used to fabricate carbon hollow nanospheres. In the second step, the extracted green inhibitor was loaded into the nanospheres (WE@MCHNSs) and on-demand active coating was fabricated by uniformly dispersing doped carbon nanospheres in epoxy matrix. The corrosion protection properties of the coatings were studied by electrochemical impedance spectroscopy (EIS), electrochemical noise measurement (ENM) and salt spray analysis. Corrosion resistance of the mild steel samples in the 3.5 wt. % NaCl solution in the presence and absence of walnut extract was compared. Salt spray and electrochemical impedance spectroscopy (EIS) results proved active protective behavior of the epoxy coating containing the doped MCNSs. It was shown that charge transfer resistance of the bare steel sample enhanced from ~ 610 Ω cm2 to ~ 4060 Ω cm2 in the presence of WE after 24 h immersion time. Also, the active corrosion protective performance of the scribed coatings was improved ~ 1450 % in the presence of WE@MCHNSs. The obtained results revealed that on-demand release of walnut green inhibitors from carbon nanospheres enhance protection performance of epoxy coatings. Furthermore, the fabricated epoxy coating demonstrated active protection behavior due to release of inhibitor caused by mechanical damage of carbon nanospheres shells (Figure 1). Please click Additional Files below to see the full abstract

A novel and cost-effective double-capsule nanocomposite coating based on carbon hollow spheres with self-healing performance for corrosion protection

The ability of a cost-effective self-healing nanocomposite system to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this research, a self-healing epoxy coating was fabricated by incorporation of carbon hollow spheres (CHSs) doped separately with epoxy and polyamine as film forming agents. Graphene-based CHSs were synthesized via silica templating method in presence of sucrose as a carbon precursor. After encapsulation of epoxy and polyamine agents in CHSs denoted as Ep-DCSs and Am-DCSs, respectively, 10 wt. % and 5 wt. % of Ep-DCSs and Am-DCSs were introduced in an epoxy matrix. The final nanocomposite coating was applied on the surface of mild steel substrates. A blank epoxy coating was also used as a control sample. The synthesized CHSs were characterized before and after the silica core removal using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The CHSs loaded with the film forming agents were evaluated using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the protective and self-healing properties of the coatings were studied using electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and salt spray testing. The obtained results showed that the fabricated nanocomposite epoxy coating can heal appropriately the scratches applied on the surface of the coating barricading the accessibility of corrosive species to the metal substrate (Figure 1). Please click Additional Files below to see the full abstract