Efficient corrosion inhibition by sugarcane purple rind extract for carbon steel in HCl solution: mechanism analyses by experimental and in silico insights

Experimental accompanied with computational (atomic/electronic)-level simulation investigations of Polygonum cuspidatum root extract as sustainable corrosion inhibitor for mild steel in aggressive corrosive media

This study investigates the corrosion inhibition potential of Polygonum cuspidatum root extract (PCRE) on mild steel in a 0.5 M HCl acidic environment. Herein, various techniques including electrochemical and gravimetric measurements were employed, along with scanning electron microscopy (SEM) and contact angle (CA) measurements for surface morphology analysis. The impedance study revealed a concentration-dependent enhancement in corrosion resistance, classifying PCRE as a mixed-type inhibitor (i.e., inhibits both anodic and cathodic reactions). The highest efficiency, 96.71% at 298 K, was observed at a 1000-ppm PCRE concentration. Langmuir model computations suggested chemisorption and physisorption of PCRE on the electrode substrate. Increased Rp (from 28.648 to 174.01 Ω) and Rct (185.74 Ω cm2) at 1000 ppm demonstrated improved corrosion resistance. Additionally, SEM analysis displayed a uniform, protective surface, reducing metal degradation. Theoretical calculations highlighted strong interactions between PCRE and mild steel, with a low energy gap (ΔE), as follows: 1-O-methylemodin (2.267 eV) < emodin (2.288 eV) < emodin-1-O-glucoside (2.343 eV) < piceid (2.931 eV) < resveratrol (2.952 eV), confirming PCRE's excellent micro-level anti-corrosion capabilities. This eco-benign corrosion inhibitor offers sustainable, low-toxicity protection, cost-effectiveness, and versatile performance, surpassing commercial counterparts while aligning with sustainability goals.

Experimental and theoretical investigations of the effect of bis-phenylurea-based aliphatic amine derivative as an efficient green corrosion inhibitor for carbon steel in HCl solution

A novel bis-phenylurea-based aliphatic amine (BPUA) was prepared via a facile synthetic route, and evaluated as a potential green organic corrosion inhibitor for carbon steel in 1.0 M HCl solutions. NMR spectroscopy experiments confirmed the preparation of the targeted structure. The corrosion inhibitory behavior of the prospective green compound was explored experimentally by electrochemical methods and theoretically by DFT-based quantum chemical calculations. Obtained results revealed an outstanding performance of BPUA, with efficiency of 95.1% at the inhibitor concentration of 50 mg L-1 at 25 °C. The novel compound has improved the steel resistivity and noticeably reduced the corrosion rate from 33 to 1.7 mils per year. Furthermore, the adsorption study elucidates that the mechanism of the corrosion inhibition activity obeys Langmuir isotherm with mixed physisorption/chemisorption modes for BPUA derivatives on the steel surface. Calculated Gibb's free energy of the adsorption process ranges from -35 to -37 kJ mol-1. The SEM morphology analysis validates the electrochemical measurements and substantiates the corrosion-inhibiting properties of BPUA. Additionally, the eco-toxicity assessment on human epithelial MCF-10A cells proved the environmental friendliness of the BPUA derivatives. Density functional theory (DFT) calculations correlated the inhibitor's chemical structure with the corresponding inhibitory behavior. Quantum descriptors disclosed the potentiality of BPUA adsorption onto the surface through the heteroatom-based functional groups and aromatic rings.

Investigation of Dracocephalum extract based on bulk and nanometer size as green corrosion inhibitor for mild steel in different corrosive media

In recent years, green corrosion inhibitors derived from natural plant resources have garnered much interest. In the present work, at first, we investigated the corrosion behavior of mild steel (st-37) in the presence, and absence of Dracocephalum extract based on bulk size as a corrosion inhibitor in two widely used acidic environments (0.5 M H₂SO₄, and 1.0 M HCl), at room temperature. Then, we used Dracocephalum extract based on nanometer size to reduce the optimal concentration of inhibitor, increase the corrosion resistant, and efficiency. Dracocephalum extract does not contain heavy metals or other toxic compounds, and also good characteristics such as low cost, eco-friendly, and widespread availability, make it suitable nature candidate as an environmentally safe green inhibitor. The anticorrosive behavior was assessed using electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP). In all of the studies, the inhibitory efficiency (IE%) increased as the extract dose was increased. But by using nano extract, in addition to maintaining high efficiency, the amount of inhibitor was reduced significantly. The highest IE% is 94% at the best dose of nano extract (75 ppm), but the highest IE% is 89% at the best dose of the bulk extract (200 ppm) in H₂SO₄ solution. Also, for the HCl solution, the highest IE% is 88% at the best dose of nano extract (100 ppm), but the highest IE% is 90% at the best dose of the bulk extract (400 ppm), by polarization method. The PP results suggest that this compound has an effect on both anodic, and cathodic processes, and that it adsorbs on mild steel surface according to the Langmuir adsorption isotherm. Optical microscopy, scanning electron microscopy (SEM) analysis, and a solid UV-Visible reflection spectrum were used to investigate the alloys' surface morphology.

Dragon Fruit Peel Extract Enriched-Biocomposite Wrapping Film: Characterization and Application on Coconut Milk Candy

Bio-based film is an eco-friendly alternative to petroleum-based packaging film. The effects of biocomposite wrapping film enhanced with dragon fruit peel extract (0, 2% w/v, respectively) and currently used commercial packaging film (polypropylene; PP) on coconut milk caramels during storage (30 °C, 75% RH, nine days) were studied. Both 0% and 2% DPE-enriched biocomposite films were thicker and had higher water vapor permeability and solubility than the PP film but poorer mechanical characteristics. In addition, the 2% film possessed antioxidants and antioxidant ability. A FESEM micrograph revealed the rough surface and porous path of the biocomposite films. Over the storage time, the moisture content, water activity, and springiness of the coconut milk caramel candy wrapped in the PP and all DPE-enriched biocomposite films were not significantly altered. However, the lipid oxidation as the thiobarbituric acid reactive substance (TBARS) and hardness of all coconut caramels were significantly (p < 0.05) increased during storage. Furthermore, the hardness of coconut candy covered in the control (0% DPE) biocomposite film was more pronounced on day nine of storage. However, the changes in quality characteristics of the coconut candy wrapped in each film type need to be better established. The investigating factors influencing the quality deterioration of coconut milk candy should be further identified to mitigate their effects and extend the shelf-life of the coconut candy.

Optimized Anticorrosion of Polypyrrole Coating by Inverted-Electrode Strategy: Experimental and Molecular Dynamics Investigations

To improve the poor adhesion and the ensuing insufficient anticorrosion efficacy of electropolymerized polypyrrole (PPy) on copper surface, an inverted-electrode strategy was applied after the passivation procedure, for which the compact coating (PPy-I) was deposited on the substrate in a cathodic window. Morphological and physical characterizations revealed that PPy-I exerted satisfactory adhesion strength and suitable thickness and conductivity compared with the analogue prepared via the traditional protocol (PPy-T). Potentiodynamic polarization, electrochemical impedance spectroscopy and frequency modulation were employed to ascertain the propitious protection of PPy-I for copper in artificial seawater (ASW). Due to the dominant electroactivity, the PPy-I-coated sample possessed higher apparent current density and lower charge transfer resistance than its PPy-T-protected counterpart, which maintained the passivation of the substrate. Surface analysis also supported the viability of PPy-I for copper in ASW for a well-protected surface with inferior water wettability. Molecular dynamics simulations evidenced that PPy-I with the higher density retained efficient anticorrosion capacity on copper at elevated temperatures. Therein, the derived time-dependent spatial diffusion trajectories of ions were locally confined with low diffusion coefficients. Highly twisted pore passages and anodic protection behavior arising respectively from the tight coating architecture and electroactivity contributed to the adequate corrosion resistance of PPy-I-coated copper.

Influence of Surface Pretreatments on the Anticorrosion of Polypyrrole Electro-Polymerized Coatings for Copper in Artificial Seawater

Plasma discharging treatment (hydroxylation) was conducted on copper surfaces for the subsequent electro-polymerization procedure of polypyrrole (PPy) coating (d-PPy). The hydroxylated surface could solve the criticized adhesion strength and protection efficiency of electropolymerized coatings for metal substrate in corrosive media. Compared with the counterpart obtained via passivation pretreatment (p-PPy), a well-adhered d-PPy layer was acquired on the hydroxylated copper surface, which earned a satisfactory adhesion grade, compactness and conductivity. Appreciable protection of d-PPy was measured for copper in the artificial seawater (ASW) at 298 K via electrochemical and surface analyses. Results of electrochemical measurements indicated that d-PPy coating effectively retarded copper corrosion in ASW with a lowered corrosion current density and improved charge transfer resistance. Surface analysis revealed that the typical morphology of PPy was retained after 240 h immersion in ASW. A favorable physical barrier and anodic protection efficacy might account for the superior protection of d-PPy coating for the underlying copper. Molecular dynamics simulations for the deposition of PPy chains on pristine and hydroxylated copper planes provided a definite correlation between the theoretical calculations and experimental observations. Theoretical modelling also disclosed in-depth the anchoring nature and anticorrosive mechanism for PPy toward the hydroxylated copper in ASW.

A novel l-histidine based ionic liquid (LHIL) as an efficient corrosion inhibitor for mild steel

A novel l-histidine based ionic liquid (LHIL) was developed and successfully synthesized. Its structure was confirmed by Fourier-transform infrared spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy, 1H-NMR and high-resolution mass spectrometry. The outstanding corrosion inhibition effect of the LHIL on mild steel in 1 M hydrochloric acid was thoroughly evaluated by Tafel plots, electrochemical impedance spectroscopy, and localized electrochemical strategies. The results revealed that the corrosion of mild steel was effectively suppressed by the adsorption of LHIL on its surface, and the best inhibition efficiency reached 98.8%. The adsorption behavior of LHIL on steel obeyed the Langmuir adsorption isotherm, which involved both chemisorption and physisorption. Theoretical calculations indicated the strong chemisorption of LHIL on steel, as proved by the low energy gap (ΔE = 0.0522 eV) and high binding energy (E binding = 303.47 kcal mol-1), which clearly confirmed the effectiveness of LHIL for steel protection.