Eco-friendly corrosion inhibitors: Synergistic effect of ethanol extracts of calotropis for corrosion of mild steel in acid media using mass loss and thermometric technique at different temperatures

The inhibitive action of leaves (LV), Latex (LX) and Fruit (FT) extracts of Calotrpis procera and Calotropis gigantea on mild steel corrosion in HCl, H₂SO₄ and mixture of solutions have been studied using mass loss and thermometric technique at different temperatures. The results indicate that the ethanolic extracts functioned as a good corrosion inhibitor in both environments and inhibition efficiency increased with extracts concentration. A mechanism of chemical adsorption of the plants components on the surface of the metal is proposed for the inhibition behavior. The inhibition efficiency increases up to 86.37%.     

The effect of some B-diketo compounds on the retardation of aluminium dissolution in HCl

The inhibitive action of some B-diketo compounds on the dissolution of aluminium in 2M HCl has been investigated by hydrogen evolution, thermometric and weight loss techniques. The adsorbability of inhibitors is dependent on the basicity of the oxygen and nitrogen sites involved. The dissolution reaction of aluminium in hydrochloric acid solutions is zero order and remains so when B-diketo compounds are present. The rate constant decreases as the inhibition efficiency increases. The activation energy of the dissolution reaction increases with decreasing acid concentration and increasing inhibitor concentration. Values of the Arrhenius activation energies agree with those obtained for an activation controlled process.     

Effect of vegetal tannin on anodic copper dissolution in chloride solutions

The corrosion inhibition of copper in a 0.1 M NaCl solution in the presence of vegetal tannin using potentiodynamic techniques was studied. The tannin was extracted from Takaout galls (Tamarix articulata). The gallic acid has been used as a representative of the tannin species. The tannin are anodic inhibitors. The inhibition efficiency of the tannin evaluated from anodic polarization curves and impedance measurements is about 93.2% for a tannin concentration of 2 g/l. We noted that the presence of tannin changes the mechanism of copper dissolution in a 0.1 M NaCl solution. Microscopic scanning studies of the surface state revealed the formation of corrosion layer products. The impedance investigation allows the explanation of the inhibition process.     

Electrochemical behavior of aluminium in acidic media

The inhibitive action of the acid extracts of seeds' leaves and bark from the Ficus virens plant towards hydrochloric and sulfuric acid corrosion of aluminium is tested using mass loss and thermometric techniques. It was found that the extract acts as a good corrosion inhibitor for aluminium corrosion in all concentration of hydrochloric and sulfuric acid solution. The ellagic acid has been used as a representative of the tannin species. The tannins are anodic inhibitors. The inhibition efficiency (IE) increases as the extract concentration is increased. The effect of temperature on the IE was studied. It was found that the presence of extract increases the activation energy of the corrosion reaction. Moreover, the heat of adsorption (Q_ads) was also calculated. It was found that the Ficus virens extract provides a good protection against pitting corrosion in chloride ion containing solution.     

The role of acid anion on the inhibition of the acidic corrosion of steel by lupine extract

The inhibitive effect of lupine (Lupinous albus L.) extract on the corrosion of steel in aqueous solution of 1 M sulphuric and 2 M hydrochloric acids was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization curves indicated that the lupine extract acts as a mixed-type inhibitor. EIS measurements showed that the dissolution process is under activation control. The inhibition efficiency of the extract obtained from impedance and polarization measurements was in a good agreement and was found to increase with increasing concentration of the extract. The obtained results showed that, the lupine extract could serve as an effective inhibitor for the corrosion of steel in acid media and the extract was more effective in case of hydrochloric acid. Theoretical fitting of the corrosion data to the kinetic-thermodynamic model was tested to show the nature of adsorption.     

The role of some thiosemicarbazide derivatives in the corrosion inhibition of aluminium in hydrochloric acid

The inhibitive action of some thiosemicarbazide derivatives towards the corrosion of aluminium in 2 M HCl has been investigated by using thermometric, weight loss and hydrogen evolution techniques. The three independent techniques gave similar results. The inhibitors used were found to be weakly adsorbed on the aluminium surface through a one-step process. The order of inhibition efficiency of the inhibitors used depends on the number of adsorption sites in the molecule and their charge density, molecular size, heat of hydrogenation and formation of metallic complexes.     

Inhibitive action of some plant extracts on the corrosion of steel in acidic media

The effect of extracts of Chamomile (Chamaemelum mixtum L.), Halfabar (Cymbopogon proximus), Black cumin (Nigella sativa L.), and Kidney bean (Phaseolus vulgaris L.) plants on the corrosion of steel in aqueous 1 M sulphuric acid were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. EIS measurements showed that the dissolution process of steel occurs under activation control. Potentiodynamic polarization curves indicated that the plant extracts behave as mixed-type inhibitors. The corrosion rates of steel and the inhibition efficiencies of the extracts were calculated. The results obtained show that the extract solution of the plant could serve as an effective inhibitor for the corrosion of steel in sulphuric acid media. Inhibition was found to increase with increasing concentration of the plant extract up to a critical concentration. The inhibitive actions of plant extracts are discussed on the basis of adsorption of stable complex at the steel surface. Theoretical fitting of different isotherms, Langmuir, Flory-Huggins, and the kinetic-thermodynamic model, were tested to clarify the nature of adsorption.     

The corrosion inhibition effect of phytic acid on 20SiMn steel in saturated Ca(OH)2 solution with 1 mol L−1 NaCl

A wise strategy to hinder the degradation of the steel rebar in concrete is finding a corrosion inhibitor to resist pitting corrosion at passive state as well as the general dissolution at active dissolution state. In this paper, the corrosion inhibition effect of phytic acid (IP6) on 20SiMn steel was investigated in the simulated concrete solution with chlorides, Sat.Ca(OH)2+1 mol/L NaCl(pH=12.9), by electrochemical methods and surface analysis techniques. The results show that IP6 could prolong the incubation time of 20SiMn steel from passive to pitting corrosion and enhance the charge-transfer resistance to a certain extent with the inhibition efficiency of around 30~50%. This is ascribed to the preferential adsorption of IP6 over chloride ion on the passive film through PO4 functional groups, which lead to the formation of a compact chelation film.     

Inhibitive effect of some Schiff bases on corrosion of aluminium in hydrochloric acid solutions

Abstract

Mass loss and thermometric methods have been used to study the inhibition of aluminium corrosion in HCl solution by four Schiff bases: 2-anisalidine-pyridine; 2-anisalidine-pyrimidine; 2-salicylidine-pyridine; and 2-salicylidine-pyrimidine. Values of inhibition efficiency obtained from the two methods are in good agreement and are dependent upon the concentrations of inhibitor and acid.     

碱蚀抑制剂的研制与应用

介绍了碱蚀机理和抑制原理。从碱蚀液的稳定性,溶铝量,金相组织,腐蚀速度,月水解率等几个方面评价了抑制剂的优劣。通过试验,确定了改进的抑制剂（亦称添加剂）配方。经过生产应用证明该配方完全能满足生产需要,可使碱蚀液寿命延长两年,其有关性能指标与进口添加剂完全一致。     

Dibutyl thiourea as corrosion inhibitor for acid washing of multistage flash distillation plant

Abstract

The effect of the additive dibutyl thiourea (DBTU) on the corrosion of 70Cu–30Ni alloy and of carbon steels in HCl solutions in distilled water and in sea water at pH 1·8–2·0 was observed using the weight loss technique at temperatures between 19 and 60°C. In the absence of DBTU the corrosion of the Cu–Ni alloy is characterised by an induction period which is longer in the pure acid than in acidified sea water. Following the induction periods, the loss in weight varies linearly with time and is temperature dependent in the pure acid, but not in sea water. On the other hand, the weight loss of carbon steel in both media varies linearly with time directly from the moment of immersion. The rate of dissolution in pure HCl is greater than in acidified sea water and both are temperature dependent. The effect of concentration of DBTU on the dissolution of the two alloys in both media was tested at 60°C. In all cases inhibition of corrosion increased with additive content. The inhibition efficiencies in presence of 300 ppm DBTU amounted to 78 and 30% for Cu–Ni and 87 and 75% for carbon steel in pure HCl and acidified sea water, respectively. Weight loss experiments carried out under modified conditions suggested decomposition of DBTU when in contact with the metal surface. The results of the present investigation reveal that DBTU is not a particularly effective inhibitor for the acid washing of multistage flash distillation units.     

The isoxazolidines: the effects of steric factor and hydrophobic chain length on the corrosion inhibition of mild steel in acidic medium

Several new isoxazolidines having varying degree of steric environment and hydrophobic chain length, prepared efficiently using single-step nitrone cycloaddition reactions, are tested for corrosion inhibition of mild steel in 1 M and 5 M HCl at 50-70 °C range by gravimetric and electrochemical methods. All compounds have shown very good corrosion inhibition efficiency (IE%) in acidic solution. Steric crowding around the nitrogen centres and hydrophobic chain lengths as well as increase in temperature (in the presence of the inhibitor in the higher concentration range 100-400 ppm) are found to increase the inhibition efficiency of the isoxazolidines. Thermodynamic parameters (ΔG°_ads, ΔH°_ads, ΔS°_ads) for the adsorption process and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction in the presence of one of the isoxazolidines were determined. Experimental results agree with the Temkin adsorption isotherm. The inhibition of corrosion in 1 M HCl, influenced by both physi- and chemi-sorption, was found to be under mixed control, but predominantly under cathodic control.     

Corrosion Protection Properties of 4-[(E)-[(2,4-Dihydroxy phenyl)methylidene] amino]-6-methyl-3-sulfanylidene-2,3,4,5-tetrahydro-1,2,4-triazin-5-one [DMSTT] Toward Mild Steel in Sulfuric Acid

The inhibition of mild steel corrosion in aerated 0.5 N H₂SO₄ solution was investigated using potentiodynamic polarization studies (Tafel), linear polarization studies, electrochemical impedance spectroscopy studies, adsorption studies, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, the effect of temperature, degree of surface coverage, adsorption kinetics, and surface morphology are investigated. The inhibition efficiency increased markedly with increase in the additive concentration and decreased slightly with increasing temperature. The presence of DMSTT decrease the double-layer capacitance and increase the charge transfer resistance. The value of activation energy (E _a) of metal corrosion, adsorption equilibrium constant (K _ads), and free energy of adsorption (ΔG _ads) were calculated from the temperature dependence of corrosion current. The adsorption of inhibitor molecule on mild steel surface follow Langmuir isotherm. DMSTT offers excellent inhibition properties and acts as a mixed-type inhibitor.     

Effects of Solution Hydrodynamics on Corrosion Inhibition of Steel by Citric Acid in Cooling Water

Corrosion is a major problem in cooling water systems, which is often controlled using corrosion inhibitors. Solution hydrodynamics is one of the factors affecting corrosion inhibition of metals in these systems. The present work focuses on the study of the combined effects of citric acid concentration (as a green corrosion inhibitor) and fluid flow on corrosion of steel in simulated cooling water. Electrochemical techniques including Tafel polarization and electrochemical impedance spectroscopy were used for corrosion studies. Laminar flow was simulated using a rotating disk electrode. The effects of solution hydrodynamics on inhibition performance of citric acid were discussed. The citric acid showed low inhibition performance in quiescent solution; however, when the electrode rotated at 200 rpm, inhibition efficiency increased remarkably. It was attributed mainly to the acceleration of inhibitor mass transport toward metal surface. The efficiencies were then decreased at higher rotation speeds due to enhanced wall shear stresses on metal surface and separation of adsorbed inhibitor molecules. This article is first part of authors’ attempts in designing green inhibitor formulations for industrial cooling water. Citric acid showed acceptable corrosion inhibition in low rotation rates; thus, it can be used as a green additive to the corrosion inhibitor formulations.     

Organic molecules showing the characteristics of localised corrosion aggravation and inhibition

The behaviour of imidazoline and an acid functionalised resorcinarene as steel corrosion inhibitors in carbon dioxide (CO₂)-saturated brine solutions has been studied using an electrochemically integrated multi-electrode array namely the wire beam electrode (WBE). Both imidazoline and resorcinarene acid provided excellent inhibition to general CO₂ corrosion; however imidazoline was found to aggravate localised corrosion by creating a small number of major anodes that focused on a small area of the WBE surface, leading to highly concentrated anodic dissolution. The resorcinarene acid showed distinctively different behaviour by generating a large number of minor anodes randomly distributing over the WBE surface, leading to insignificant general anodic dissolution. These results indicate that resorcinarene acid provided effective localised corrosion inhibition by promoting a random distribution of insignificant anodic currents.     

Corrosion Inhibition of Carbon Steel in 1 M Hydrochloric Acid using Some Pyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]Pyrimidnone Derivatives

The inhibiting effect of three compounds of pyrazolo[3,4-d] pyrimidnone derivatives toward the corrosion of carbon steel in 1.0M HCl solution was investigated using galvanostatic and potentiodynamic anodic polarization techniques. The rise of the concentration of the inhibitors and decreasing the temperature led to the greater of inhibition efficiency. The inhibiting action of these compounds was explicated on the footing of its adsorption on the carbon steel surface. The adsorption operation of these compounds was obeyed Langmuir isotherm. There is only one anodic peak during the anodic cyclic voltammogram This peak was elucidated due to the active dissolution of Fe as Fe²⁺. The percentage inhibition efficiency was computed from the values of peak current density.There is a good convention between the values of the percentage inhibition efficiency gained from the diverse techniques.These compounds inhibit the pitting corrosion of carbon steel by shifiting the pitting corrosion potential to more noble direction. The effect of elevation of temperature on the rate of corrosion in devoid of and containing these compounds was studied and some activated thermodynamic parameters were computed.     

Study of the dissolution of lead in nitric acid by the thermometric technique

The thermometric technique was used to study the dissolution of lead in HNO₃. It was found that ΔT and the reaction number increase almost linearly with an increase in the acid concentration to a certain limit, whereafter the reaction is inhibited by a further increase owing to the formation of a protective layer of PbO₂.The mechanism of dissolution is confirmed by the effects of some additives, e.g. NO₂^_ ion, NO₃^_ ion as KNO₃ and NH₄NO₃, Cl^_ ion as HCl and NaCl, as well as urea. These additives were found to increase or decrease the dissolution process depending on whether they or their reaction products were involved in the dissolution reaction.     

Inhibition of mild steel corrosion in phosphoric acid solution by triazole derivatives

Corrosion inhibition by triazole derivatives (n-PAT) on mild steel in phosphoric acid (H₃PO₄) solutions has been investigated by weight loss and polarization methods. The results indicate that these compounds act as mixed-type inhibitors retarding the anodic and cathodic corrosion reactions with emphasis on the former and do not change the mechanism of either hydrogen evolution reaction or mild steel dissolution. Some kinetic parameters are obtained.     

The synergistic effect of Halide ions on the corrosion inhibition of zinc by n-decylamine

The effect of halide ions on the spontaneous dissolution and the anodic and cathodic polarization of zinc in perchloric acid solution with and without n-decylamine has been studied. Halide ions enhanced the corrosion of zinc, whereas n-decylamine inhibited the corrosion of zinc. The inhibitor efficiency of n-decylamine is increased significantly by the presence of halide ions. A consistent surface coverage value is obtained both from weight loss and polarization studies. n-decylamine acts mainly as a cathodic inhibitor. The change in the free energy of adsorption of n-decylamine in the presence of halide ions is explained in terms of a change in the mechanism of corrosion inhibition. Synergism of n-decylamine and halide ions is discussed from a view point of a model of co-adsorption of halide ions and n-decylamine.     

An investigation on the effect of bleaching environment on pitting corrosion and transpassive dissolution of 316 stainless steel

Pitting corrosion and transpassive dissolution of 316 stainless steel in a solution containing five percent of commercial bleaching liquid was investigated by employing potentiodynamic polarization method and recording corrosion potential during immersion. Today commercial bleaching liquids are widely used as a cleaner additive. Therefore those house appliances made from stainless steels are in contact with aqueous solution containing bleaching liquid. This may cause severe localized corrosion and transpassive dissolution. In order to investigate the possibility of tranpassive dissolution of stainless steel by bleaching liquid, potentiodynamic polarization and recording the variation of corrosion potential of specimens were carried out in 0.2 M Na₂SO₄ solution containing 5%wt. commercial bleaching liquid. A 500 mV drop in transpassive potential and also instantaneously ennobled corrosion potential revealed the possibility of transpassive dissolution due to the oxidizing effect of the species such as free chlorine and its derivatives in bleaching liquid. Evaluation of the occurrence of localized corrosion at the presence of Cl^? and bleaching liquid was investigated by similar electrochemical experiments in 0.2 M Na₂SO₄ + 0.4 M NaCl containing 5%wt. bleaching solution. Initiation of stable pitting at potentials lower than the transpassive potential as well as a sharp increase of the corrosion potential in this environment demonstrates the possibility of pitting corrosion.