Electrochemical and computational aspects of surface interaction and corrosion inhibition of mild steel in hydrochloric acid by Phyllanthus amarus leaf extract (PAE)

Molecular Insights into the Effect of Crystal Planes on Droplet Wetting

Dynamic wetting by liquids on solid surfaces depends on several aspects such as surface energy, roughness, and interfacial tension, among many others. Copper (Cu), gold (Au), aluminum (Al), and silicon (Si) are a few of the most important metals that are used extensively as substrates in various industrial and biomedical applications. Metals are etched frequently on different crystal planes for fabrication purposes. Etching exposes distinct crystal planes that may come in contact with the liquids when used for different applications. The interaction of the crystal planes with the liquid that comes in contact with the solid dictates the wetting behavior of the surface. This necessitates the importance of understanding how various crystal planes of the same metals behave under similar conditions. Herein, three specific crystal planes, namely, (1 0 0), (1 1 0), and (1 1 1), are investigated at a molecular scale for the above-mentioned metals. The dynamic contact angle and contact diameter trends revealed that the relatively hydrophobic surfaces (Cu, Si) tend to reach their equilibrium contact angle faster compared to the hydrophilic substrates (Al, Au). Molecular kinetic theory is used to estimate the three-phase contact line friction which is found to be higher for (1 1 1) planes. Further, a consistent potential energy distribution variation is observed for the crystal lattice of (1 0 0), (1 1 0), and (1 1 1). These findings can be used as a guideline to determine the factors needed to completely describe a dynamic wetting phenomenon of the droplet over the different crystal planes. The understanding will be of great use in deciding experimental strategies where fabricated different crystal planes would be required to have a liquid contact.

An insight into the potent medicinal plant Phyllanthus amarus Schum. and Thonn

Phyllanthus amarus Schum. and Thonn., a globally distributed herb is known for its several therapeutic potentials. P. amarus has a long history of use in the traditional system of medicine for over 2000 years owing to its wide array of secondary metabolites that confer significant medicinal attributes. Research on various aspects including ethnobotany, phytochemistry to bioactivity, or pharmacological studies has been conducted over the past several decades on this potent herb. P. amarus extracts have shown a broad range of pharmacological activities like hepatoprotective, antioxidant, antiviral, antimicrobial, antidiabetic, anti-inflammatory, anticancer, antimalarial, nephroprotective, diuretic, and several other properties. The present review compiles and covers literature and research of several groups across past decades to date and focuses on how the therapeutic significance of this plant can be further explored for future research either as herbal formulations, alternative medicine, or in the pharmaceutical industry.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13237-022-00409-z.

Insight into the corrosion inhibition of Biebersteinia multifida root extract for carbon steel in acidic medium

In this project, the protective effect of Biebersteinia multifida root extract (BMRE) against corrosion of 1018 low carbon steel (1018LCS) in HCl solutions was appraised by assessing weight loss, electrochemical impedance spectroscopy (EIS), and polarization at 25 °C. The maximum inhibitory efficacy for the concentration of 1 g/l of the BMRE was 92.8% at 25 °C after 2 h and increased to 95.3% after 24 h of immersion. Polarization experiments have shown that the extract in acidic solutions can act as a mixed corrosion inhibitor. The corrosion inhibitory efficacy of BMRE decreased with increasing temperature, and at all temperature settings studied, the adsorption of BMRE molecules on 1018 LCS was consistent with the Langmuir adsorption isotherm. The Scanning Electron Microscopy (SEM) analysis confirmed the protection of 1018 LCS in the acidic solution containing BMRE extract. Quantum chemistry studies of four main constituents of the extract called vasicinone, umbelliferon, scopoletin, and ferulic acid were performed by density functional theory, DFT, in neutral and protonated states. Calculated quantum parameters were used to investigate the active sites and donor-receptor interactions of molecules.

Cucumber (Cucumis sativus L.) Leaf Extract as a Green Corrosion Inhibitor for Carbon Steel in Acidic Solution: Electrochemical, Functional and Molecular Analysis

An extract of cucumber leaves (ECSL) was prepared as a green corrosion inhibitor for carbon steel. Its carbon steel corrosion inhibition performance against 0.5 mol L⁻¹ H₂SO₄ was investigated using electrochemical methods and scanning electron microscopy (SEM). Its composition was analyzed by gas chromatography and mass spectroscopy (GC−MS). Quantum chemical calculations and molecular dynamics simulations (MDS) were conducted to elucidate the adsorption mechanism of the inhibitor molecules on the carbon steel surface. The results indicated that the inhibition efficiency increases with its increasing concentration. The extract acted as a mixed type corrosion inhibitor, and its inhibition properties were ascribed to the geometric coverage effect induced by its adsorption on the metal surface in accordance with Langmuir’s law. The active components in the extract were identified as mainly organic compounds with functional groups such as aromatic moieties and heteroatoms. The inhibition activities of ECSL are delivered through the ability of the active components to adsorb on the metal surface through their functional groups to form a protective layer which hinders the contact of aggressive substances with carbon steel and thus suppresses its corrosion. This research provides an important reference for the design of green corrosion inhibitors based on plant waste materials.

A Brief Review on Fruit and Vegetable Extracts as Corrosion Inhibitors in Acidic Environments

The corrosion of metals, i.e., the initiation and acceleration of the surface deterioration of metals through an electrochemical reaction with the surrounding intrusive environment, is a global concern because of the economic and environmental impacts. Corrosion inhibitors are considered the most practical choice among the available corrosion protection techniques due to their effectiveness in terms of functionality and cost. The use of traditional and toxic corrosion inhibitors has led to environmental issues, arousing the need for green counterparts that are environmentally friendly, easily accessible, biodegradable, and cost-effective. In this review, the utilization of green corrosion inhibitors purely acquired from renewable sources is explored, with an in-depth focus on the recent advancements in the use of fruit and vegetable extracts as green corrosion inhibitors. In particular, fruits and vegetables are natural sources of various phytochemicals that exhibit key potential in corrosion inhibition. To shed light on the true potential of such extracts in the protection of steel in acidic environments, the experimental techniques involved in corrosion inhibition and the mechanism of corrosion inhibition are discussed in detail. The study highlights the potential of fruit and vegetable extracts as non-toxic, economical, and effective corrosion inhibitors in the pursuit of green chemistry. In addition to discussing and outlining the current status and opportunities for employing fruit and vegetable extracts as corrosion inhibitors, the current review outlines the challenges involved in the utilization of such extracts in corrosion inhibition.

The co-adsorption of thymohydroquinone dimethyl ether (THQ) and coumarin present in the aqueous extract of Ayapana triplinervis on mild steel and its protection in hydrochloric acid up to 323 K: computational and physicochemical studies

This study evaluates the corrosion inhibition property of the aqueous and alcoholic leaf extracts of the medicinal plant Ayapana triplinervis. The major components in the extracts are thymohydroquinone dimethyl ether (THQ) and coumarin. It is clear from the weight-loss studies that the water extract of the leaves (AYW) is superior to the alcoholic extract (AYA) in terms of offering corrosion inhibition. The 96% efficiency of 4% (v/v) AYW in 0.5 N HCl at room temperature changes to 84.62% at 323 K. The mixed-type inhibition behaviour of AYW shows slight dominance in the anodic direction. Studies suggest the multilayer adsorption of phytochemicals on the metal surface and that the adsorption follows the Temkin model. Theoretical studies using DFT and BIOVIA Materials Studio investigations establish THQ as a good inhibitor with high adsorption characteristics. Even though the concentration of coumarin in the extract is low, its presence in the extract facilitates the adsorption of THQ on the metal surface, which is evident from the MD simulation study. The changes in the surface topography and elemental composition of the metal specimen in the inhibited and uninhibited solution are monitored by SEM and EDX spectral studies. XPS data support the presence of both THQ and coumarin on the metal surface and the existence of co-ordinate bonding between the metal's d orbital and the O atoms of THQ. Theoretical and experimental studies support the mixed mode of adsorption of THQ as physisorption followed by chemisorption.

This study evaluates the corrosion inhibition property of the aqueous and alcoholic leaf extracts of the medicinal plant Ayapana triplinervis.

Corrosion Inhibition Using Harmal Leaf Extract as an Eco-Friendly Corrosion Inhibitor

Extract of natural plants is one of the most important metallic corrosion inhibitors. They are readily available, nontoxic, environmentally friendly, biodegradable, highly efficient, and renewable. The present project focuses on the corrosion inhibition effects of Peganum Harmala leaf extract. The equivalent circuit with two time constants with film and charge transfer components gave the best fitting of impedance data. Extraction of active species by sonication proved to be an effective new method to extract the inhibitors. High percent inhibition efficacy IE% of 98% for 283.4 ppm solutions was attained using impedance spectroscopy EIS measurements. The values of charge transfer Rct increases while the double layer capacitance Cdl values decrease with increasing Harmal extract concentration. This indicates the formation of protective film. The polarization curves show that the Harmal extract acts as a cathodic-type inhibitor. It is found that the adsorption of Harmal molecules onto the steel surface followed Langmuir isotherm. Fourier-transform infrared spectroscopy FTIR was used to determine the electron-rich functional groups in Harmal extract, which contribute to corrosion inhibition effect. Scanning electron microscopy SEM measurement of a steel surface clearly proves the anticorrosion effect of Harmal leaves.

A Review on Plants and Biomass Wastes as Organic Green Corrosion Inhibitors for Mild Steel in Acidic Environment

Acid corrosion is a problem pertaining to corrosion that involves an acid solution. It is important to treat metal to preserve its integrity. Thus, acids are utilized to clean and treat metal surfaces. In return, this may lead to over-etching and metal degradation. Corrosion inhibitors were introduced as a solution for the issue. However, there are some problems associated with the usage of conventional corrosion inhibitors. Traces of nitrites and chromates that are present in the inhibitors may lead to serious health and environmental issues. As a solution, organic green corrosion inhibitors have been studied to replace the conventional corrosion inhibitors. These inhibitor molecules form a protective layer on top of the metal surface to suppress metal dissolution when added to the acid solution. This process prevents direct contact between the metal surfaces and the acid environment. This study explores the usage of natural resources and biomass wastes as the basis for organic green corrosion inhibitors. This study also provides some suggestions for new biomass wastes that can be studied as new organic corrosion inhibitors, and it is aimed at opening the perspective of researchers on exploring new organic inhibitors by using natural resources and biomass wastes.

Inhibition of Mild Steel Corrosion in 1M Hydrochloric Medium by the Methanolic Extract of Ammi visnaga L. Lam Seeds

The chemical composition of the methanolic extract of Ammi visnaga (Khella) seeds from the Sidi Slimane region is determined for the first time by Gas Chromatography coupled with Mass Spectrometry (GC/MS). Ten compounds representing 99.638% of the total extract were identified. Khellin (49.011%), Visnagin (26.537%) and Dimethylethylamine (15.108%) are the major components. Moreover, the inhibitory effect of the Methanolic extract of the seeds of Ammi visnaga on the corrosion of mild steel in a solution of 1M HCl is determined using weight loss measurements, the potentiodynamic technique as well as the technique of electrochemical impedance spectroscopy (EIS). It is found that the extract reduces the corrosion rate of the steel in the acid solution. Inhibition efficiency increases as the concentration of the extract increases. The tested compound has an inhibition efficiency of 84% for a concentration equal to 1.0 g/L. The polarization measurements indicate that the examined extract acts as a mixed inhibitor with predominant anodic efficacy. The data obtained from EIS studies are analyzed to model this process using appropriate equivalent circuit models. The adsorption of the extract on the surface of the mild steel obeys the Langmuir adsorption isotherm in acidic medium and the activation is determined and discussed.

The protection mechanism offered by Heterophragma adenophyllum extract against Fe-C steel dissolution at low pH: Computational, statistical and electrochemical investigations

An ethanolic extract of Heterophragma adenophyllum (HA) was investigated as a corrosion inhibitor for Fe-C steel in hydrochloric acid. The inhibition effect of the HA extract was examined using weight deterioration, electrochemical impedance spectroscopy (EIS) and polarization techniques. EIS showed enhanced charge transfer resistance with a maximum protection value of ~96% at 600 ppm concentration. Tafel extrapolation results revealed that corrosion was restricted by mixed inhibition. The i_corr values reduced considerably from 53.63 μA cm^-2 at 100 ppm to 20.11 μA cm^-2 at 600 ppm of HA extract. Interaction intensity was further examined through Langmuir, Freundlich, D-R, Frumkin, and Flory-Huggins adsorption isotherms. The computational study, statistical modelling and surface morphology by XPS, AFM, and SEM-EDX, indicated an excellent adsorption capability of HA on Fe-C steel.

Green biocide for mitigating sulfate-reducing bacteria influenced microbial corrosion

In the present investigation, Polyalthia longifolia plant extract (PLAE) was used as biocide to control corrosion in the presence of sulfate-reducing bacteria (SRB). Transmission electron microscopy showed the damage of SRB outer cell membrane which lead to cell destruction and disturbed membrane permeability. The scanning electron microscopy also confirmed the cell shrinkage due to green biocide, and energy-dispersive Fourier transform infra-red spectroscopy indicated the decrease in sulfide concentration in the presence of biocide. Potentiodynamic polarization of mild steel showed the lower in corrosion rate due to the decrease in cathodic reduction kinetics of SRB in the presence of biocide PLAE. The gravimetric mass loss also showed corrosion rate dropped from 0.064 millimeter per year (mm/year) to 0.013 mm/year with and without biocide. The present study showed that P. longifolia extract could be a novel biocide against the growth of the SRB to control corrosion in oil and gas industries.