In this report, two chromotrope dyes, chromotropic acid (CA) and chromotrope 2R (CR), were explored as inhibitors against mild steel corrosion in 1.0 M sulfuric acid solutions at 303 K. Electrochemical, spectroscopic, chemical, and microscopic techniques, namely, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy, mass loss, and scanning electron microscopy (SEM), have been employed to evaluate the inhibition efficiencies (%IEs) of the examined organic dyes. The %IEs were found to increase with the inhibitors’ concentrations, while they decreased with rising temperature. The outcomes of the PDP technique displayed that the examined inhibitors operated as mixed-type inhibitors with anodic prevalence. The impedance spectra described by Nyquist and Bode graphs in the corrosive environment and in the presence of various concentrations of the examined inhibitors showed single depressed capacitive loops and one-time constants. This behavior signified that the mild steel corrosion was managed by the charge transfer process. The SEM micrographs of the surfaces of mild steel samples after adding the examined inhibitors revealed a wide coverage of these compounds on the steel surfaces. Thus, the acquired high %IEs of the examined inhibitors were interpreted by strong adsorption of the organic molecules on the mild steel surface. This constructed a shielding layer separating the alloy surface from the corrosive medium, and such adsorption was found to follow the Langmuir isotherm. Furthermore, the evaluated thermodynamic and kinetic parameters supported that the nature of such adsorption was mainly physical. Results obtained from all employed techniques were consistent with each other and revealed that the %IE of the CR inhibitor was slightly higher than that of CA under similar circumstances. Finally, the mechanisms of both corrosion of mild steel in sulfuric acid solutions and its inhibition by the tested organic dyes were also discussed.

Metal surfaces can become damaged by corrosion when they interact with their surroundings, leading to huge financial losses. The use of corrosion inhibitors is one of the most crucial ways to combat the risky and hazardous effects of corrosion. In the present research, electrochemical techniques and surface analysis have been used to characterize the inhibition properties of (3-hydroxy-4-((4-nitrophenyl)diazenyl)-5-(phenylamino)thiophen-2-yl)(phenyl)methanone for the corrosion of carbon steel in an aerated 1.0 M HCl solution. Steel’s corrosion resistance was discovered to be improved by the presence of the examined inhibitor in 1.0 M HCl medium through the adsorption of the inhibitor species to create a barrier layer. The findings showed that when inhibitor concentrations increased and solution temperatures decreased, the inhibition performance (%IE) of the compound under study enhanced. In the light of inhibitor probe’s chemical makeup and theoretical analysis, the mechanism of the inhibition process was addressed. In a 1.0 M HCl solution containing 5 × 10⁻⁵ M of the inhibitor, the inhibition performance, at room temperature, was found to be almost 97%. The electrochemical results revealed that the examined compound successfully prevented carbon steel corrosion as a mixed-type inhibitor. The Langmuir and Freundlich isotherms are pursued by the adsorption of the examined inhibitor. Additionally, using Arrhenius and transition state equations, the activation thermodynamic parameters ΔE_a, ΔH*, and ΔS* were determined and explained. The adsorption process was illustrated using DFT computation and MC simulations. The experimental findings and theoretical simulations concurred surprisingly well. Finally, the paper presents a discussion of the inhibitory mechanism.

Herein, the inhibition impacts of chitin, pectin, and amylopectin as carbohydrate polymers on the corrosion of mild steel in 0.5 M HCl were researched utilizing various experimental and theoretical tools. The acquired outcomes showed that the inhibition efficiencies (% IEs) of the tested carbohydrate polymers were increased by raising their concentrations and these biopolymers acting as mixed-kind inhibitors with major anodic ones. The acquired % IEs values were reduced with rising temperature. The higher % IEs of the tested polymers were inferred via powerful adsorption of the polymeric molecules on the steel surface and such adsorption obeyed the Langmuir isotherm. The computed thermodynamic and kinetic quantities confirmed the mechanism of physical adsorption. The kinetics and mechanisms of corrosion and its protection by polymeric compounds were illuminated. The results obtained from all the techniques used confirmed that there was good agreement with each other, and that the % of IEs followed the sequence: chitin > amylopectin > pectin.

This study investigated different amino acid-based surfactants (AASs), also known as biosurfactants, including sodium N-dodecyl asparagine (AS), sodium N-dodecyl tryptophan (TS), and sodium N-dodecyl histidine (HS) for their potential anticorrosion, antibacterial, and antidermatophyte properties. The chemical and electrochemical techniques were employed to examine the copper corrosion inhibition efficacy in H₂SO₄(1.0 M) solution at 298 K. The results indicated their promising corrosion inhibition efficiencies (% IEs), which varied with the biosurfactant structures and concentrations, and the concentrations of corrosive medium. Higher % IEs values were attributed to the surfactant adsorption on the copper surface and the production of a protective film. The adsorption was in agreement with Langmuir adsorption isotherm. The kinetics and mechanisms of copper corrosion and its inhibition by the examinedAASswere illuminated. The surfactants behaved as mixed-kind inhibitors with minor anodic priority. The values of % IEs gained from weight loss technique at a 500 ppm of the tested surfactants were set to be 81, 83 and 88 forAS, HSandTS, respectively. The values of % IEs acquired from all the applied techniques were almost consistent which were increased in the order:TS > HS ≥ AS, establishing the validity of this study. These surfactants also exhibited strong broad-spectrum activities against pathogenic Gram-negative and Gram-positive bacteria and dermatophytes.HSexhibited the highest antimicrobial activity followed byTS, andAS. The sensitivity of pathogenic bacteria varied against testedAASs.Shigella dysenteriaeandTrichophyton mantigrophyteswere found to be the most sensitive pathogens.HSexhibited the highest antibacterial activity againstShigella dysenteriae, Bacillus cereus, E. coli,K. pneumoniae,andS. aureusthrough the formation of clear zones of 70, 50, 40, 39, and 35 mm diameters, respectively.AASsalso exhibited strong antifungal activity against all the tested dermatophyte molds and fungi.HScaused the inhibition zones of 62, 57, 56, 48, and 36 mm diameters againstTrichophyton mantigrophytes,Trichophyton rubrum, Candida albicans, Trichosporon cataneum,andCryptococcus neoformans, respectively.AASsminimal lethal concentrations ranged between 16 to 128 µg/ml.HSpresented the lowest value (16 µg/ml) against tested pathogens followed byTS(64 µg/ml), andAS(128 µg/ml). Therefore,AASs, especiallyHS,could serve as an effective alternative antimicrobial agent against food-borne pathogenic bacteria and skin infections-associated dermatophyte fungi.

The inhibitory impacts of two expired drugs, namely, azithromycin (AZM) and roxithromycin (RXM) towards the corrosion of mild steel (MS) in 1.0 M H₂SO₄ solution were examined exploiting potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss techniques. The results obtained from various employed techniques indicate that increasing the concentration of examined expired drugs and reducing the temperature increased the inhibition efficiencies. Potentiodynamic polarization indicated that the expired AZM and RXM drugs acted as mixed-type inhibitors, but the cathode was highly polarized, β_c > β_a. The inhibiting power of these compounds is interpreted based on their adsorption on the surface of MS. The adsorption process obeys Langmuir isotherm. Impedance data confirmed that MS corrosion is under charge transfer control and the adsorption of both expired drugs on the MS surface led to the formation of protective film. The inhibition efficiency of RXM is greater than that of AZM due to the increased molecular weight and number of electron donating group within the expired drug. Activation and adsorption thermodynamics parameters were computed and interpreted. The adsorption process is spontaneous and endothermic. GRAPHICAL ABSTRACT

During the mandatory acidification process in the oil and gas industry, carbon steel unfortunately suffers significant corrosion damage. From this perspective, for the first time a new ionic liquid called 1-(2-(4-bromophenyl)-2-oxoethyl)-4-(tert-butyl)pyridin-1-ium bromide (ILB) has been used as an effective inhibitor for the carbon steel corrosion in aggressive HCl solution (15%) at 298 K. The experiments were managed with a number of different chemical and electrochemical techniques including weight loss, potentiodynamic polarization (PDP), and impedance spectroscopy (EIS). ILB has good inhibitory performance as an acidizing corrosion inhibitor for carbon steel even at low dosing levels of 1 × 10⁻³ M. The findings were promising as an inhibition efficiency of about 97% was achieved when ILB was added at low concentrations to the corrosive media. EIS results showed a significant rise in charge transfer resistance (R_ct) values with increasing doses of ILB. PDP studies confirmed that ILB is a mixed type and obey Langmuir adsorption isotherm with chemical nature. The metal surface morphologies were inspected using a Scanning Electron Microscope (SEM) and an Atomic Force Microscope (AFM). Additionally, Density Functional Theory (DFT) and Molecular Dynamic Simulation (MDS) indicates that ILB molecules function as inhibitors more successfully. There is a high degree of concordance between practical and theoretical studies.