Use of a theoretical prediction method and quantum chemical calculations for the design, synthesis and experimental evaluation of three green corrosion inhibitors for mild steel

Autonomous-healing and smart anti-corrosion mechanism of polyurethane embedded with a novel synthesized microcapsule containing sodium dodecyl sulfate as a corrosion inhibitor

The self-healing and smart anti-corrosion behavior of a polyurethane coating enhanced with micro-sized capsules have been investigated. An in situ polymerization technique was employed to synthesize a novel microcapsule containing sodium dodecyl sulfate (SDS) as a corrosion inhibitor in linseed oil (LO). FE-SEM, FT-IR and TG analysis were used to characterize the prepared microcapsules. The capsules were separately embedded in polyurethane at 1, 4 and 7 wt% and the coating properties were investigated through the water absorption rate and pull-off adhesion strength. The scratched coating was then subjected to 3.5 wt% NaCl solution to investigate the self-healing ability. Electrochemical measurements were carried out by means OCP, EIS and potentiodynamic polarization and the inhibition mechanism of SDS was discussed in terms of interfacial interactions. Despite the adhesion strength, a positive effect was observed for the water uptake, after addition of the microcapsules. 4 wt% of LO/SDS microcapsules showed the best results as its inhibition efficiency was more than 90% compared to single linseed oil capsules. EDS mapping was also employed to verify the successful release and distribution of the SDS, when subjected to scratching.

Innovative Method for Longer Effective Corrosion Inhibition Time: Controlled Release Oil Palm Empty Fruit Bunch Hemicellulose Inhibitor Tablet

This study aims to develop a controlled release oil palm empty fruit bunch hemicellulose (EFB-H) inhibitor tablet for mild steel in 1 M HCl. As plant extracts tend to deteriorate at longer immersion time, limiting its industrial applicability, we attempted to lengthen the inhibition time by forming a controlled release inhibitor tablet. Electrochemical methods (potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)) were employed to investigate the efficiency and mechanism of the inhibition. An optimum dosage and immersion time was determined via Response Surface Methodology (RSM). EFB-H tablet was formulated using D-optimal mixture design, and its anticorrosion action at extended immersion time was compared with EFB-H powder. PDP measurement revealed that EFB-H is a mixed type inhibitor. RSM optimization unveiled that the optimum point for a maximum inhibition efficiency (87.11%) was at 0.33 g of EFB-H and 120 h of immersion time. Tablet T3 with EFB-H to gum Arabic to hydroxypropyl methylcellulose ratio of 66:0:34 portrayed the best tensile strength (0.243 MPa), disintegration time (152 min) and dissolution behavior. EFB-H tablet exhibited a longer-lasting inhibition effect than powder, which was 360 h as compared to 120 h for powder. Overall, EFB-H tablet has been successfully developed, and its enhanced effective inhibition time has been experimentally proven.

Plant Extracts as Green Corrosion Inhibitors for Different Metal Surfaces and Corrosive Media: A Review

Natural extracts have been widely used to protect metal materials from corrosion. The efficiency of these extracts as corrosion inhibitors is commonly evaluated through electrochemical tests, which include techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss measurement. The inhibition efficiency of different extract concentrations is a valuable indicator to obtain a clear outlook to choose an extract for a particular purpose. A complementary vision of the effectiveness of green extracts to inhibit the corrosion of metals is obtained by means of surface characterizations; atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy analysis are experimental techniques widely used for this purpose. Moreover, theoretical studies are usually addressed to elucidate the nature of the corrosion inhibitor—metal surface interactions. In addition, calculations have been employed to predict how other organic substances behave on metal surfaces and to provide experimental work with fresh proposals. This work reports a broad overview of the current state of the art research on the study of new extracts as corrosion inhibitors on metal surfaces in corrosive media. Most constituents obtained from plant extracts are adsorbed on the metal, following the Langmuir adsorption model. Electron-rich regions and heteroatoms have been found to be responsible for chemisorption on the metal surface, whereas physisorption is due to the polar regions of the inhibitor molecules. The plant extracts compiled in this work obtained corrosion inhibition efficiencies above 60%, most of them around 80–90%. The effect of concentration, extraction solvent, temperature, and immersion time were studied as well. Additional studies regarding plant extracts as corrosion inhibitors on metals are needed to produce solutions for industrial purposes.