New triazepine carboxylate derivatives: correlation between corrosion inhibition property and chemical structure

Development of Natural Plant Extracts as Sustainable Inhibitors for Efficient Protection of Mild Steel: Experimental and First-Principles Multi-Level Computational Methods

In the present work, we present the superior corrosion inhibition properties of three plant-based products, Fraxinus excelsior (FEAE), Zingiber zerumbet (ZZAE), and Isatis tinctoria (ITAE), that efficiently inhibit the corrosion of mild steel in phosphoric acid. The anti-corrosion and adsorption characteristics were assessed using a combination of experimental and computational approaches. Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy methods were used to evaluate the inhibitive performance of the inhibitors on the metal surface. Then, both DFT/DFTB calculations and molecular dynamic simulations were further adopted to investigate the interaction between organic inhibitor molecules and the metal surface. The protective layers assembled using the active constituents, such as carbonyl and hydroxyl groups, of the three plant-based products offer high electrochemical stability at high temperatures and robust protection against aggressive acidic solutions. All electrochemical measurements showed that the inhibition performance of extracts increased by increasing their concentration and improved in the following order: FEAE > ZZAE > ITAE. Further, these extracts worked as mixed-type inhibitors to block the anodic and cathodic active sites on the mild steel surface. Multi-level computational approaches revealed that FEAE is the most adsorbed inhibitor owing to its ability to provide electron lone pairs for electrophilic reactions. The experimental and theoretical results showed good agreement. These results indicate the possibility of replacing conventional compounds with natural substituted organic products in the fabrication of hybrid materials with effective anti-corrosion performance.

Corrosion Inhibition, Adsorption and Thermodynamic Properties of Poly (Sodium 4-Styrenesulfonate) on Carbon Steel in Phosphoric Acid Medium

The use of polymers as corrosion inhibitors has attracted much attention due to their low prices, inherent stability, availability and cost-effectiveness. The corrosion inhibiting effect of poly(sodium-4-styrenesulfonate) on carbon steel in phosphoric acid solution has been investigated using weight loss and scanning electron microscopy techniques (SEM) and theoretical calculations based on density functional theory (DFT). In the presence of 1.0×10-3 mol/L of inhibitor, a maximum inhibition effect of 98.06 % was observed. The influence of the concentration of the inhibitor, the temperature of the solution and the immersion time on the corrosion of carbon steel was investigated. Activation parameters such as activation energy (Eact), activation enthalpy (ΔHact), activation entropy (ΔSact), heat of adsorption (Qads) and adsorption free energy (ΔGads) were evaluated based on the effect of temperature on the corrosion and inhibition processes. It was found that the adsorption behaviour of poly(sodium-4-styrenesulfonate) (PSS) follows the Langmuir isotherm and the free energy change values indicate mixed chemical and physical adsorption on the carbon steel surface. The results obtained with the different methods agree well.

Exploration of synthesized quaternary ammonium ionic liquids as unharmful anti-corrosives for aluminium utilizing hydrochloric acid medium

1-(benzyloxy)-1-oxopropan-2-aminium 4-methylbenzenesulfonate (BOPAMS) and 4-(benzyloxy)-4-oxobutan-1-aminium 4-methylbenzenesulfonate (BOBAMS) were prepared and confirmed through spectroscopic methods (FT-Infrared, Carbon 13-NMR and Proton-NMR). BOPAMS and BOBAMS were evaluated as unharmful inhibitors for aluminium corrosion. The anti-corrosive properties, inhibition mechanism, inhibitor-metal adsorption behaviour and corrosion inhibition efficiency were evaluated by employing approaches like gravimetric, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). FT-IR demonstrated functional groups that are responsible for the binding of BOPAMS and BOBAMS with surfaces of aluminium. BOPAMS and BOBAMS resemble a semi-chemisorption/physisorption mechanism, obeying Langmuir binding model. The mechanism of binding adopted by BOPAMS and BOBAMS was proposed.