Graphene oxide nano-layers functionalized/reduced by L-Citrulline/Pectin bio-molecules for epoxy nanocomposite coating mechanical properties reinforcement

In this work, graphene oxide (GO) was reduced/modified by an eco-friendly route using L-Citrulline molecules extracted from the watermelon rind. Before and after the modification/reduction process, the rGO layers were characterized by different spectroscopy techniques. In addition, the mechanical properties of the epoxy-rGO reinforced coatings were evaluated by tensile and dynamic mechanical thermal analysis (DMTA) tests. The characterization results have demonstrated that the GO nanosheets were successfully reduced/modified by the extracted compounds. DMTA analysis showed that the values of storage modulus at glassy and rubbery regions for the neat epoxy sample incorporated with the rGO nanosheets were increased by about 39 % and 97 %, respectively. Moreover, the glass transition temperature (Tg) was increased from 76.8 °C for the neat epoxy (EP) to 84.0 °C for the EP/modified-reduced GO nanocomposite. Tensile tests showed that the values of tensile strength, maximum strain, elastic modulus, and toughness of the epoxy-based coating were respectively increased by about 142 %, 266 %, 46.7 %, and 388 % after incorporation of the rGO nanosheets compared to the EP sample

Modified hydroxyethyl cellulose as a highly efficient eco-friendly inhibitor for suppression of mild steel corrosion in a 15% HCl solution at elevated temperatures

Natural polymer-based corrosion inhibitors have been studied for the prevention of steel corrosion in various corrosive environments over recent years, yet they did not show impressive inhibition performance especially at high temperatures. The present study introduces a facile and practical method to enhance the inhibition activity of natural polymers (hydroxyethyl cellulose (HEC) as a carbohydrate model) on the basis of polyurethane chemistry. The ability of chemically modified hydroxyethylcellulose (CHEC) in suppressing mild steel (MS) corrosion was assessed using weight loss, electrochemical impedance spectroscopy (EIS), open circuit potential (OCP), and potentiodynamic polarization (PDP) techniques, and further confirmed by field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). All electrochemical measurements revealed that the incorporation of only 1% of polyurethane prepolymer to the CHEC structure greatly enhanced its inhibition efficiency in the acidic solution, even at high temperatures. CHEC adsorbed on the MS surface and functioned as a mixed-type inhibitor, with a maximum inhibition efficiency of 93% at 80 °C. In addition, the morphology of MS surface in the presence of CHEC confirmed the protective role of the additive and XPS results clearly revealed CHEC adsorption on the MS surface. Furthermore, density functional theory computations and molecular dynamics simulations provided corroborating molecular-level insights on the electronic structure of CHEC and its interactions with the metal surface. These findings demonstrate that the polyurethane prepolymer method is a new and effective approach for enhancing the anticorrosion performance of natural polymer-based corrosion inhibitors in aggressive acidic media at high temperatures