Increasing Inhibitor Concentration Research Articles

Abstract 172: Limiting medulloblastoma progression by hindering the Hedgehog signaling pathway with novel atypical protein kinase C inhibitors

Abstract Medulloblastoma is the most common pediatric brain tumor, constituting 20% of all childhood brain cancers (Clin. Cancer Res. 2008, 14 (4), 971-976., Oncogenesis 2019, 8 (11), 1-11). It is a highly invasive tumor that originates in the cerebellum and has the ability to metastasize throughout the central nervous system early in its course. The median age of diagnosis is 5 years, with 80% of cases being diagnosed in the first 15 years (Asian J. Neurosurg. 2015, 10 (1), 1-4). Current treatment options include maximal safe resection, chemotherapy and craniospinal radiation (J. Neurosurg. Pediatr. 2019, 24(4), 353-363). Despite such aggressive therapeutic treatments, nearly 30% of afflicted patients succumb to this disease, and survivors cope with the long-term side effects of these treatments that have significant impacts on their quality of life (J. Neurosurg. Pediatr. 2019, 24(4), 353-363). This underscores the need for less invasive and more effective treatment methods to improve overall patient outcomes. We believe that oncogene expression resulting from the Hedgehog (Hh) signaling pathway is responsible for upregulating malignant cancer cell growth, cell survival, and migration. Preliminary dose curve studies, in which D341 and D283 medulloblastoma cell lines were treated with novel atypical protein kinase C (aPKC) inhibitors 2-acetyl-1,3-cyclopentanedione (ACPD) and 3,4-diaminonapthalene-2,7-disulfonic acid (DNDA) (Int. J. Oncol. 2017, 51(5), 1370-1382), have been shown to significantly decrease cell proliferation with increasing inhibitor concentration. Cell line D341 showed 44.2% inhibition when treated with 10 µM of ACPD and 75.2% inhibition when treated with 1 µM of DNDA while cell line D283 showed a 63.2% inhibition at 5 µM of ACPD and 73.6% inhibition at 10 µM. Future studies will be conducted to determine the inhibition mechanism of the Hh pathway in medulloblastoma by probing for different cell cycle and oncoprotein markers using Western blotting, employing the WST-1 assay to evaluate cell viability and cytotoxicity, and implementing migration and invasion assays. Citation Format: Luke Lajmi, Sloan Breedy, Wishrawana S. Ratnayake, Mildred Acevedo-Duncan. Limiting medulloblastoma progression by hindering the Hedgehog signaling pathway with novel atypical protein kinase C inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 172.

Newly Synthesized Morpholinyl Mannich Bases as Corrosion Inhibitors for N80 Steel in Acid Environment.

New Mannich bases, 3-morpholino-1-phenylpropan-1-one (MPO) and 3-morpholino-1-phenyl-3-(pyridin-4-yl) propan-1-one (MPPO), were synthesized, characterized, and studied as corrosion inhibitors for N80 steel in 1 M hydrochloric acid (HCl) solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and FT-IR spectroscopy. The inhibition efficiency increases with increasing inhibitor concentrations, and the corrosion inhibition efficiency of the MPO and MPPO could reach 90.3% and 91.4%, respectively, at a concentration of 300 ppm at 305 K. The effect of the temperature on the corrosion inhibition behavior of inhibitors was discussed. Electrochemical tests showed that the synthesized inhibitors are mixed. The EIS test results showed that the presence of MPO and MPPO reduced the double-layer capacitance in the corrosion process, thereby reducing the charge transfer resistance. The SEM and EDX results showed that the MPO and MPPO formed a uniform adsorption film on the surface of the N80 steel. The adsorption mechanism of the inhibitors was simulated with different adsorption models and the results showed that the inhibitors were the chemisorbed type. The results of the FT-IR spectroscopy proved that the inhibitor interacted with metal atoms on the steel surface.

Synthesis and characterization of N-(2-aminophenyl)- 2-(5-methyl-1H-pyrazol-3-yl) acetamide (AMPA) and its use as a corrosion inhibitor for C38 steel in 1 M HCl. Experimental and theoretical study

A new synthesized organic compound namely N-(2-aminophenyl)-2-(5-methyl-1H-pyrazol-3-yl) acetamide (AMPA), its structure was identified based on spectral data 1H NMR and 13C NMR, its inhibiting effect against the corrosion of C38 steel in a 1 M HCl solution has been studied by experimental and theoretical studies. The experimental studies are performed using electrochemical tests, while the theoretical studies are performed using density functional theory (DFT) calculations and Monte Carlo simulations. The results obtained show that AMPA is an effective inhibitor against the corrosion of C38 steel in an acid medium, and that its performance efficiency reaches 93% for a concentration of 5 mM. The polarization curves show that AMPA functions as a mixed inhibitor; its adsorption on the C38 steel surface undergoes the Langmuir isotherm. The electrochemical impedance spectra indicate that the value of the charge transfer resistance increases with increasing inhibitor concentrations and with increasing immersion time. The surface morphology of C38 steel in the absence and in the presence the inhibitor was analyzed by scanning electron microscopy (SEM) combined with EDX analysis. Computer calculations of synthetic corrosion inhibitor are employed to study the role of their molecular skeleton of AMPA in the corrosion inhibition process. The calculated results support the empirical results.

Poor recovery of fungal denitrification limits nitrogen removal capacity in a constructed Gulf Coast marsh

Widespread degradation and destruction of coastal wetlands over the last century have spurred on the practice of creating salt marshes to mitigate losses of wetland area and ecosystem function. Constructed marshes can quickly recover plant biomass, but biogeochemical functions, such as nitrogen removal capacity through denitrification, can take decades to centuries to recover. One potential mechanism for this uncoupling of structural and functional recovery is that an impaired microbial community subsequently impedes the nitrogen removal capacity of constructed marshes. While both bacteria and fungi can contribute to nitrogen removal via denitrification, little is known about fungal denitrification in wetlands, even though it has the potential to contribute to climate change via the production of the greenhouse gas nitrous oxide. Here, we measured fungal and bacterial denitrification potential rates and fungal biomass in sediments collected from a 33-year-old constructed marsh and a reference natural marsh to assess both a) the relative contribution of each group to total nitrogen removal and b) whether fungal biomass accrual is a driver of functional recovery in salt marshes. To assess the relative contributions of fungi and bacteria to denitrification, we added selective inhibitors (antifungal, antibacterial, or both) to sediments from each marsh and measured potential fungal and bacterial denitrification rates. We also measured sediment ergosterol concentrations seasonally as a proxy for fungal biomass. In the absence of inhibitors, denitrification potential rates in the constructed marsh were three times lower than in natural marsh sediment. Further, denitrification rates in the constructed marsh remained similarly low regardless of increasing inhibitor concentration, whereas denitrification rates in the natural marsh declined with increasing inhibitor concentration. When either inhibitor was added alone, denitrification was stimulated in the natural marsh, but was suppressed in the constructed marsh, suggesting an apparent competitive release, where the reduction of either bacterial or fungal competition for substrate thereby allowed the remaining competitor greater access to the substrate, in the natural marsh. We observed that compared to the constructed marsh, fungi in the natural marsh contributed ∼30% more (50% vs. 21%) to denitrification, and that fungal biomass was generally higher. Collectively, these data suggest that 3 decades post construction, denitrification rates and the contribution of fungal denitrification to total denitrification are lower in the constructed marsh than the natural marsh. These data also suggest that fungal biomass may limit the recovery of nitrogen removal in constructed marshes and that fungal denitrification can be an important pathway of N removal in salt marsh ecosystems.

Identification of Reactive Dye Transfer Source and Comparison of Two Types of Dye Transfer Inhibitors

The source for reactive dye transfer of cotton fabric varies in different studies, and there is limited information on the washing factors. This study explored the source of Reactive Red 195 colored cotton fabric dye transfer and reported the effects of three key washing factors and their interactions with two types of dye transfer inhibitors. First, the high-performance liquid chromatography results show that the peak of completely hydrolyzed Reactive Red 195 matches the peak of the washing residue of the fabric colored by Reactive Red 195. The dye transfer process is positively related to the hydrolyzed dyes. Based on this, response surface method models for the three factors, water consumption, water hardness, and dye transfer inhibitors concentration for polyvinylpyrrolidone and lauryl betaine were built. Both response surface method models show that due to the presence of Ca2+ and Mg2+, the increase in water hardness reduces the zeta potential on the fabric surface, and causes a decrease of electrostatic repulsion between the dye and the fabric. The dye transfer inhibiting effect is reduced. The increase in dye transfer inhibitor concentration strengthened the effect of inhibiting the transfer of hydrolyzed Reactive Red 195. In addition, there is a cross effect between water hardness and dye transfer inhibitor concentration. There is optimal water hardness and dye transfer inhibitor concentration to maximize the inhibition of hydrolyzed Reactive Red 195 dye transfer. The water consumption shows a limited effect because the washing time is long enough to reach a balance in the fabric and washing fluids. Polyvinylpyrrolidone with many hydrophilic groups is easy to combine with hydrolyzed dyes. While lauryl betaine is a small molecule surfactant, the structural differences make the response surface method model show that polyvinylpyrrolidone has a better effect than lauryl betaine. The discoveries can be used to guide dye transfer inhibitor development. Further investigations, including dye transfer inhibitor synthesis and modification, are needed.

Inhibiting Effect of Natural Plant Leaves Extract Used as Green Corrosion Inhibitor for Mild Steel in Acidic Media

Abstract: Inhibition of corrosion of mild steel in hydrochloric acid by natural plant leaves extract of of Bahunia Varigata (Aapta), Azadirachta Indica (Neem), Pongamia Pinnata (Karanj), Santalum Album (Sandal Wood) and Astonia Scholaris (Saptparni) has studied using weight loss measurement. It was, found that the leaves extract act as a good corrosion inhibitor for mild steel in all concentrations of the extract. The inhibition action depends on the concentration of the leaves extract in the acid solution. Results for weight loss measurements indicate that inhibition efficiency increase with increasing inhibitor concentration. 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. Several organic compounds with heteroatom such as N, O, S and P present in the plant extracts are, adsorbed directly onto the metals surface through polar atoms and thereby forming the protective layer. Plants represent a class of interesting source of compounds currently being, explored for use in metal corrosion protection in most systems, as possible replacement of toxic synthetic inhibitors. This paper discusses the different types of natural green plant leaves extract inhibitors for corrosion control of mild steel in acid medium. Keywords: Corrosion, Inhibition, carbon steel, Weight loss and natural plant leaves extract.

Corrosion resistance and metallurgical behaviour of CMT welded Al-LCS dissimilar butt joint exposed in simulated industrial environment

Cold Metal Transfer welding is a predominant process for joining the Aluminium and Low Carbon Steel (LCS) dissimilar joints with enhanced properties. In addition, these joints have vast application in various simulated industrial environmental conditions. However, the formation of thick intermetallic layers during welding over these joints leads to invoking the corrosion attack and causing a catastrophic failure that is the primary concern in life prediction of the joint. Hence, the corrosion behaviour of AL-LCS dissimilar butt joint exposed in the simulated industrial environment has been studied experimentally and it has been compared with the Cold Metal Transfer (CMT) welded aluminium and LCS similar joints. The potentiodynamic polarization and the electrochemical impedance spectroscopy were carried out in 3.5% aggressive sodium chloride medium with varying benzotriazole corrosion inhibitor with varying the concentrations like 10 ppm, 15 ppm and 20 ppm. The results showed that the corrosion resistance behaviour of CMT welded dissimilar joints are increased with increasing inhibitor concentration. The inhibitor showed effective performance, and the efficiency is also found to be 78–80% at 20ppm, which revealed the enhanced corrosion resistance of dissimilar metal joints in simulated industrial conditions. Finally, the dissimilar joints are characterized by sophisticated analytical techniques.

Schiff Bases Derived from Triazoles as Corrosion Inhibitors for Maraging Steel in Acid Mixtures: Experimental and Theoretical Studies

The ability of two triazole derived Schiff bases, namely,4-[(furan-2-ylmethylidene)amino]-5-methyl-4H-1,2,4-triazole-3-thiol [FAMTT] and 4-[(4-chlorobenzylidene)amino]-5-methyl-4H-1,2,4-triazole-3-thiol [CAMTT], to inhibit corrosion of maraging steel by 2:1 mixture of HCl and H2SO4 was evaluated. Temperature range of 30-45 °C and inhibitor concentration range of 5-25 ppm for FAMTT and 5-50 ppm for CAMTT were employed. An increase in inhibitor concentration and temperature resulted in an increase of inhibition efficiencies of both inhibitors. The inhibition efficiencies of FAMTT were significantly larger than CAMTT in weight loss studies, a maximum of 94.4% observed at 25 ppm for FAMTT and a maximum of 82.4% at 50 ppm observed for CAMTT. However, in the electrochemical studies, though FAMTT performed better than CAMTT, the differences in their efficiencies were somewhat less than that observed in weight loss method. In polarization studies, FAMTT showed maximum efficiency of 96.2% at 25 ppm and 45 °C, while, CAMTT showed a maximum of 90.8% at 50 ppm and 45 °C, and, in electrochemical impedance studies (EIS), maximum efficiency was 97.4% at 25 ppm and 45 °C for FAMTT, and 96.5% at 50 ppm and 45 °C for CAMTT. Inhibition properties of both were verified by kinetic and thermodynamic analyses. Both exhibited mixed type inhibitory action by chemisorbing on the metal surface and followed Langmuir adsorption isotherm. The adsorption of the inhibitors on the steel surface was confirmed by Scanning Electron Microscopy-Energy-dispersive X-ray studies (SEM-EDS) analyses. Density Functional Theory (DFT) calculations were made to predict the inhibition property, and to correlate molecular structure with the corrosion inhibition property. There was a good agreement between experimental observation and theoretical prediction- that FAMTT has higher inhibition potential than CAMTT.

Modulation of the monomer-dimer equilibrium and catalytic activity of SARS-CoV-2 main protease by a transition-state analog inhibitor

The role of dimer formation for the onset of catalytic activity of SARS-CoV-2 main protease (MProWT) was assessed using a predominantly monomeric mutant (MProM). Rates of MProWT and MProM catalyzed hydrolyses display substrate saturation kinetics and second-order dependency on the protein concentration. The addition of the prodrug GC376, an inhibitor of MProWT, to MProM leads to an increase in the dimer population and catalytic activity with increasing inhibitor concentration. The activity reaches a maximum corresponding to a dimer population in which one active site is occupied by the inhibitor and the other is available for catalytic activity. This phase is followed by a decrease in catalytic activity due to the inhibitor competing with the substrate. Detailed kinetics and equilibrium analyses are presented and a modified Michaelis-Menten equation accounts for the results. These observations provide conclusive evidence that dimer formation is coupled to catalytic activity represented by two equivalent active sites.

Effect of 3-Nitroacetophenone on Corrosion Inhibition of Mild Steel in Acidic Medium

Acetophenone derivatives are eco-friendly corrosion inhibitors to prevent corrosion of mild steel (MS) in acidic medium. In this work, the inhibition effect of 3-nitroacetophenone (3-NA) on the corrosion of MS in acidic medium (1 N HCl) was investigated using weight loss measurements, electrochemical measurements, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and quantum chemistry analysis. The studies were performed using different concentrations of inhibitors and at different temperatures. The results indicated that the inhibition efficiency of 3-NA increases with an increase in inhibitor concentration and reaches to a maximum of 64% at inhibitor concentration of 250 ppm at 30°C. The potentiodynamic polarization measurement indicated that 3-NA acts as mixed category of interdict. The adsorption of 3-NA on MS surface followed the Langmuir adsorption isotherm. The mode of adsorption of 3-NA on MS surface was further studied by quantum chemical calculations based on density functional theory (DFT). The results plainly revealed that 3-NA performs fairly as corrosion interdict for MS in acidic medium.

Adsorption and Inhibition Analysis of Aconitine and Tubocurarine Alkaloids as Eco-friendly Inhibitors of Pitting Corrosion in ASTM – A47 Low Carbon Steel in HCl Acid Environment

Corrosion is an enormous challenge in all sectors of the economy, especially to those working with metals. The research on the adsorption and inhibition analysis of aconitine alkaloid (ACA) and tubocurarine alkaloid (TBA) as eco-friendly inhibitors of pitting corrosion in ASTM – A47 low carbon steel in HCl acid was carried out under the following experimental methods: gravimetric method, gasometric method, electrochemical impedance spectroscopy, potentiodynamic polarization, and scanning electron microscopy. Results revealed good inhibitors as inhibition efficiencies were recorded at 98.8% and 91.2% at a maximum inhibitor concentration of 1500 ppm for tubocurarine and aconitine alkaloids, respectively. The inhibition efficiency was found to increase with increasing inhibitor concentrations indicating a strong binding between inhibitor molecules and ASTM – A47 low carbon steel in HCl acid. Electrochemical data strongly supported the efficacy of both inhibitors as earlier presented by the chemical methods as a trend in values of charge transfer resistance, double layer capacitance, corrosion potential, and corrosion current density were in accordance with standards for a good inhibitor. The inhibitors were seen to be spontaneous, stabled, endothermic and physically adsorbed. Adsorption of the inhibitors on metal surface obeyed Langmuir, El-Awady, Freundlich, and Temkin adsorption isotherm as regression values were approximately unity.

Corrosion Inhibition of Mild Steel in Sulphuric Acid Solution with Tetradenia riparia Leaves Aqueous Extract: Kinetics and Thermodynamics

One of the most successful ways for maximizing profit and lowering costs is to use mild steel over other corrosion-resistant alloys. As a result, mild steel is the most commonly used metallic material in many industries, and its corrosion resistance has received a lot of attention. The mild steel corrosion inhibition using compounds derived from plants is the most practicable and preferable technique because of their linked low cost and green chemistry credentials. This study reports on the kinetics and thermodynamics of mild steel corrosion inhibition in sulphuric acid media utilizing Tetradenia riparia leaves aqueous extract as a potential green inhibitor. The investigations were carried out using the gasometric technique. The findings indicated that the corrosion inhibition efficiency (IE) increased with increasing inhibitor concentration with an optimal value of 90.6% at 500-ppm. The increase in temperature 298 to 338 K lowered the corrosion inhibition efficiency by only 4%. The adsorption kinetics of the extract on the mild steel fit into Langmuir, Temkin, EL-awady, and Freundlich models, but the Langmuir was the best. The results of this investigation show that adsorption of the extracted chemicals on mild steel in a sulphuric acid solution is feasible and most likely involves a combination of physical and chemical adsorption.

Study of the Corrosion Inhibition Reaction of Admixed Plant Distillates on Mild Steel

The corrosion inhibition reaction of plant distillates and their synergistic combination effect was studied. Atlas cedarwood distillate (ACW), and admixture of sage and Jojoba distillates (SJA), and admixture of jojoba and lavender distillates (JLD) were evaluated at minimal concentrations to for their corrosion inhibition effect on mild steel in 1 M H2SO4solution. Results showed ACW reacted poorly at 1% and 2% inhibitor concentration. However, from 3% - 6% ACW concentration the final corrosion rate of 94.73%, 94.77% and 95.61% was attained at 240 h signifying effective inhibition performance. SJA inhibitor compound exhibited optimal performance at all concentrations (1% - 6% SJA) with maximum inhibition value of 98.44% at 5% SJA concentration. JLD exhibited optimal performance at all concentrations studied after 2% JLD with maximum inhibition value of 91.07% at 3% JLD concentration and 240 h exposure time. The mean values for ACW and JLD inhibition efficiency appreciated with increase in inhibitor concentration while the value for SJA compound was generally constant. Results shows the extent of variation from mean values (standard deviation) for ACW and JLD was significantly high compared to the values obtained for SJA compound where the deviation from mean value is below 2. The Margin of error values for ACW and JLD compound shows that 65% and 60% of inhibition efficiency data have values above 70% inhibition efficiency compared to SJA where 100% of its inhibition efficiency data have values above 70% inhibition at +12.07%, +13.58% and +0% and +13.58%. Statistical analysis ANOVA only inhibitor concentration of the compounds significantly influenced their inhibition performance with values of 66.61%, 70.29% and 93.07% (ACW, SJA and JLD compound) compared to exposure time which had no influence. However, confirmation comparison of the mean square ratio of the compounds with the theoretical statistical tables shows the inhibitor concentration for JLD only is statistically relevant.

Antibacterial and anticorrosion behavior of bioactive complexes of selected transition metal ions with new 2‐acetylpyridine Schiff base

AbstractSuccessful preparation of Schiff base 4‐(4‐aminophenoxy)‐N‐(1‐(pyridin‐2‐yl)ethylidene)aniline derived from refluxing of 4,4‐oxydianniline with 2‐acetylpyridine within 2 h in 1:1 molar ratio was performed. Different transition metal complexes were synthesized by reacting metal chlorides with the formed ligand in 1:1 molar ratio. Structural features of the complexes were obtained from different tools such as infrared (IR), 1H‐nuclear magnetic resonance (1H‐NMR), ultraviolet–visible (UV‐vis), molar conductivity, thermogravimetric (TG)/differential thermogravimetric (DTG), microanalysis, and mass spectrometry. All complexes had an octahedral structure and Schiff base acted as a neutral bidentate ligand that linked to metal centers via N‐azomethine and N‐pyridine atoms. Cr(III), Fe(III), and Ni(II) complexes were electrolytes while other complexes were nonelectrolytes. The molecular structure of Schiff base was optimized theoretically and its HOMO and LUMO energies were dictated by B3LYP/DFT calculations. The in vitro antibacterial activity versus some selected bacteria species showed that all prepared compounds were biologically active except Fe(III) complex against certain species and Co(II) complex had the highest biological activity values. Molecular docking was used to determine effective binding modes between ligand and its [Co(L)(H2O)2Cl2]·4H2O complex with active sites of 4WJ3, 4ME7, 4K3V, and 3T88 receptors. The strongest binding of Co(II) complex was with the 4ME7 receptor with lowest binding energy value −25.4 kcal mol−1. Schiff base as corrosion inhibitors for mild steel in 1.0‐M HCl had been investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP), and electrochemical frequency modulation (EFM). The results showed that the inhibitor acts as a mixed‐type inhibitor. The inhibition efficiency increases with increasing inhibitor concentration to its maximum of 97.5% at 1 × 10−3 M solution. The adsorption model obeys the Langmuir isotherm, and Gibbs free energy was around −40 kJ/mol, indicating that it is spontaneously and chemically adsorbed on the surface. SEM/EDX results proved the sticking of a barrier film on the mild steel sample.

Electrochemical behaviour of carbon steel in sodium chloride solution by using thiophenol derivative inhibitor

The corrosion inhibition performance of thiophenol has been evaluated for carbon steel immersed in sodium chloride solution by weight loss method. As a results of weight loss method, it gives the corrosion rate and inhibition efficiency. The increase of corrosion inhibition efficiency with increase in concentration of thiophenol derivative inhibitor. When increase in concentration of inhibitor, the corrosion rate decreases. It is because of the higher concentration of inhibitor solution which arrest the active site of a carbon steel by the way of forming protective layer on the surface of carbon steel. The mechanistic aspects of corrosion inhibition has been assessed by electrochemical studies such as potentio dynamic polarisation studies and AC impedance spectra. The decrease of corrosion current and double layer capacitance value, increase in linear polarisation resistance values and impedance values obtained from electrochemical studies suggest that the formation of protective layer on the carbon steel surface. Surface analysis of polished, corroded and inhibitor carbon steel surface has been evaluated by SEM.

Experimental and quantum chemical studies of synergistic enhancement of the corrosion inhibition efficiency of ethanol extract of Carica papaya peel for aluminum in solution of HCl

The investigation of ethanol extract of Carica papaya (EECP) as an inhibitor for the corrosion of aluminum in solutions of HCl was facilitated through gravimetric, gasometric, potentiodynamic polarization and quantum chemical methods. The ccorrosion rate for the blank systems was 1.66 × 10−4 mpy but in the presence of various concentrations (0.1 to 0.5 g/dm3) of EECP, it reduces from 1.32 × 10−4 mpy to 0.96 × 10−4 mpy respectively while the inhibition efficiencies ranged from 20.93 to 42.04 % respectively. However, a synergistic combination of various concentrations of the inhibitor with 0.6 M of KBr, KI and KCl enhanced the inhibition efficiency to the following ranges: 75.44 to 87.41 %, 50.20 to 71.89 % and 77.44 to 88.73 % respectively. Potentiodynamic polarization and gasometric results were in good agreement but revealed that ethanol extract of Carica papaya peel acted as cathodic type inhibitor. Calculated activation energies indicated increasing retardation strength with an increase in inhibitor concentration and supported physisorption mechanism. The adsorption of the extract on the aluminum surface was exothermic, spontaneous, and occurred with an increasing degree of orderliness. Freundlich and Temkin's isotherms were most suitable in explaining the adsorption behaviour of the extract. Molecular structures that actively participated in the corrosion inhibition (papain, riboflavin, retinol, niacin and alpha-tocopherol) have been modeled through the calculations of global and local reactivity indices. Molecular simulation studies were also conducted to estimate the interaction between the inhibitor and the metal surface and the results indicated strong involvement of heteroatoms and aromatic rings in the adsorption process. The study concluded, that although the inhibition efficiency of EECP is low, enhancement with potassium halides can give an excellent score towards the management of waste through resource recovery.

Inhibitory action of xylenol orange on aluminum corrosion in hydrochloric acid solution

The inhibition effect of xylenol orange on the corrosion of aluminum (2S Grade) in 0.4-0.6 M HCL over the temperature range 313-333K has been studied. Both thermodynamic parameters and kinetic parameters with the inhibition effect have been correlated. The inhibition efficiencies of xylenol orange are investigated by weight loss and potentiodynamic polarization methods. The corrosion rate of aluminum decreases with increasing inhibitor concentrations and the efficiency of inhibition increases with increasing concentration of inhibitor up to almost 87% in 0.4M HCL and up to 84% in 0.6M HCL. The concentrations of inhibitor have been kept in the range 2-8 mM. It is also observed that the inhibition efficiency decreases with increasing HCl concentration and temperature. The adsorption of inhibitor on the aluminum surface obeys the Langmuir adsorption isotherm equation. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic parameters. The experimental data have been successfully related with adsorption theory and kinetic equations. Polarization curves show that xylenol orange is a mixed-type inhibitor in hydrochloric acid.

Electrochemical and Economic Evaluation of the Cocoa Bean Shell as a Corrosion Inhibitor in Acidic Medium

The inhibition effect of the cocoa bean shell powder (CBSP) on SAE 1008 carbon steel was studied in acidic medium (HCl 0.5 mol L-1) by electrochemical techniques and gravimetric measurements. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were used to the chemical and morphological characterization. The gravimetric and EIS results showed that the corrosion rate decreases with increasing inhibitor concentration, reaching the maximum value of 97.92% in 1.77 g L-1 inhibitor (highest concentration studied). Even at the lowest concentration (0.44 g L-1) good corrosion inhibition efficiency (96.03%) was observed. The polarization curves indicated that the CBSP acts as a mixed type inhibitor. The inhibitory molecules adsorption followed the Langmuir isotherm model. The inhibitor economic evaluation showed that the use of CBSP is 48-616 times cheaper than traditional inhibitors. The results showed that CBSP is an efficient corrosion inhibitor for carbon steel and its production is financially attractive.

Corrosion inhibition, adsorption behaviour, and thermodynamic studies of red dragon fruit (Selenicereus costaricensis) waste peel extracts on mild steel in acidic environment

Metal corrosion is brought about by the oxidation of atoms on the surface resulting in irreversible damage to structures at staggering costs. Hence, the search for efficient and cost-effective corrosion inhibitors is relevant. In this study, the ethanolic extract of Red Dragon Fruit (Selenicereus costaricensis) waste peels (RDF) has been tested for its anti-corrosion property using the weight loss method at different temperatures (303-343 K). The calculated inhibition efficiency of 2% RDF is 97%. Thermodynamic studies reveal that increasing inhibitor concentration raises the activation parameters of mild steel in acidic media such as activation energy (Ea) and changes in enthalpy (Ho) and entropy (So). Moreover, increased immersion time, inhibitor concentration, and temperature led to increased inhibition efficiency. The spontaneous process (Go ads = -23.47 kJ/mol) of adsorption of RDF on mild steel surfaces obeys the Langmuir isotherm model. Lastly, optical microscopy of the inhibited and uninhibited systems confirms the potential of the RDF against pitting corrosion.

Insights into Corrosion Inhibition Behavior of a 5-Mercapto-1, 2, 4-triazole Derivative for Mild Steel in Hydrochloric Acid Solution: Experimental and DFT Studies

A triazole heterocyclic compound namely 3-(4-ethyl-5-mercapto-1, 2, 4-triazol-3-yl)-1-phenylpropanone (EMTP) was examined for its corrosion protection of mild steel (MS) against 1 M hydrochloric acid medium using gravimetric techniques. EMTP exhibited excellent corrosion protection performance at low and high concentrations towards MS in HCl solution. Comparison of corrosion protection performance of EMTP and its parent triazole and temperature effects of on inhibition efficacy were also studied. EMTP has potential corrosion inhibitor for mild steel in 1.0 M hydrochloric acid solution with the highest protection efficacy of 97% at 303 K. The weight loss findings implied that EMTP protects the metal surface corrosion through the creation of a protective layer at the surface mild steel–corrosive solution interface. The inhibitive efficacy increases with the increase of inhibitor concentration and decreases with increased temperature. The adsorption of EMTP on the surface of MS follows Langmuir’s adsorption isotherm process. DFT method was conducted on EMTP molecule to calculate the quantum chemical parameters and to determine the relationship between the molecular structure of EMTP and protection performance. The molecular parameters, such as energy gap and frontier molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), and the absolute electronegativity (χ) value from inhibitor molecules to unoccupied d-orbital of iron atoms on the mild steel surface were also determined and correlated with protection efficiency. The theoretical findings revealed that the protection performance of EMTP increased with the increase in HOMO energy, and the nitrogen, oxygen and sulfur atoms are most probable positions for bonding through giving electrons to the d-orbital of iron atoms on the mild steel surface.