CORROSION INHIBITION OF CARBON STEEL IN ACIDIC MEDIA BY BIFURCARIA BIFURCATA EXTRACT

The effect of extract of brown alga Bifurcaria bifurcata (Bb) on the corrosion of steel in 1 M HCl solution was studied using weight loss, potentiodynamic, and polarization resistance measurements. Experimental data revealed that Bb extract acted as an inhibitor in the acid environment. The extract was a mixed-type inhibitor, predominating as an anodic inhibitor at higher concentration. It was found that the inhibition efficiency increased with an increase in Bb extract concentration. The corrosion inhibition of Bb extract on carbon steel in 1 M HCl solution was also investigated by infrared and UV-visible spectrophotometry to obtain information on bonding mechanism between the metallic surface and the inhibitor. The process of inhibition is attributed to the adsorption of the extract molecules, the precipitation of Fe-chelates, and/or formation of complex at the electrode surface.     

INHIBITION OF MILD STEEL CORROSION IN SULFURIC ACID MEDIUM BY HYDROXYETHYL CELLULOSE

The inhibitive effect of hydroxyethyl cellulose (HEC) on mild steel corrosion in aerated 0.5 M H₂SO₄ solution was studied using gravimetric and electrochemical techniques. The effect of temperature on corrosion and inhibition was also investigated. The results show that hydroxyethyl cellulose functioned as a good inhibitor in the studied environment and inhibition efficiency increased with concentration of inhibitor. Potentiodynamic polarization measurements revealed that HEC inhibited both the cathodic and anodic partial reactions of the corrosion processes. Impedance results clearly show that HEC inhibited the corrosion reaction by adsorption onto the metal/solution interface by significantly decreasing the double layer capacitance (C _dl ). This result was greatly pronounced in the presence of the inhibitor system (HEC + KI) that contains halide additive. Temperature studies revealed an increase in inhibition efficiency with rise in temperature. The adsorption behavior was found to obey the Freundlich isotherm. The values of activation energy, heat of adsorption, and standard free energy suggest that there was transition from physical to chemical adsorption mechanism of HEC on the mild steel surface. Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency.     

CORROSION INHIBITION OF CARBON STEEL IN LOW CHLORIDE MEDIA BY AN AQUEOUS EXTRACT OF HIBISCUS ROSA-SINENSIS LINN

The inhibition efficiency (IE) of an aqueous extract of white flower, namely, Hibiscus rosa-sinensis Linn., in controlling corrosion of carbon steel immersed in an aqueous solution containing 60 ppm of Cl^-has been evaluated by the mass loss method. The flower extract (FE) shows good IE. In the presence of Zn²⁺, excellent IE is shown by the flower extract. A synergistic effect exists between the flower extract and Zn²⁺. The mechanistic aspects of corrosion inhibition have been investigated by polarization study and AC impedance spectra. Polarization study reveals that the formulation consisting of flower extract and Zn²⁺ functions as a mixed inhibitor. AC impedance spectra reveal that a protective film is formed on the metal surface. The active principle in the flower extract is quercetin-3-O-glucoside. This has been confirmed by UV-visible absorption spectra. The protective film formed on the metal surface has been analyzed by FT-IR and AFM spectra. It is found that the protective film consists of Fe²⁺-quercetin-3-O-glucoside complex and Zn(OH)₂.     

BIOMASS EXTRACTS FOR MATERIALS PROTECTION: CORROSION INHIBITION OF MILD STEEL IN ACIDIC MEDIA BY Terminalia chebula EXTRACTS

The inhibiting action of the fruit extract of Terminalia chebula (TC) on mild steel corrosion in 1 M HCl solution was studied using gravimetric, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. The experimental results showed that TC functioned as an inhibitor in the acidic corrodent and that corrosion inhibition efficiency increased with extract concentration. Cathodic and anodic polarization curves show that TC functioned as a mixed-type inhibitor, while impedance results show that the extract organic matter was adsorbed at the metal/corrodent interphase. A computational study of the adsorption behavior of some of the organic constituents of the extracts was carried out using density functional theory (DFT). The computations were used to theoretically ascertain the individual contributions of the constituents to the observed corrosion-inhibiting effect of the extract.     

BENEFICIAL ROLE OF SURFACTANTS AS CORROSION INHIBITORS IN PETROLEUM INDUSTRY: A REVIEW ARTICLE

The objective of this review is to outline the beneficial role of surfactants as corrosion inhibitors in the petroleum field. After an introduction and brief notes on fundamentals of surfactants, the article shows the most important corrosion problems in the oil industry and the effective role of surfactants to solve these problems. The reported mechanisms of corrosion inhibition by surfactants are also considered. Key results are extracted from publications covering the past 50 years.     

THE ROLE OF PHOSPHONATE DERIVATIVES ON THE CORROSION INHIBITION OF STEEL IN HCL MEDIA

The inhibition of corrosion of steel by two P-containing compounds, sodium methyldodecyl phosphonate and sodium methyl (11-smethacryloyloxyundecyl) phosphonate, in hydrochloric acid has been investigated at various temperatures using electrochemical techniques (impedance spectroscopy (EIS), potentiodynamic polarization) and weight loss measurements. Inhibition efficiency (E%) increased with phosphonate concentration. Adsorption of inhibitors on the steel surface in 1 M HCl follows the Langmuir isotherm model. EIS measurements showed that the dissolution process of steel occurred under activation control. Polarization curves indicated that inhibitors tested acted as cathodic inhibitors. The temperature effect on the corrosion behavior of steel in 1 M HCl without and with the inhibitor was studied in the temperature range from 313 to 353 K. The adsorption free energy and activation parameters for the steel dissolution reaction in the presence of phosphonates were determined.     

THE ROLE OF PHOSPHONATE DERIVATIVES ON THE CORROSION INHIBITION OF STEEL IN HCL MEDIA

The inhibition of corrosion of steel by two P-containing compounds, sodium methyldodecyl phosphonate and sodium methyl (11-smethacryloyloxyundecyl) phosphonate, in hydrochloric acid has been investigated at various temperatures using electrochemical techniques (impedance spectroscopy (EIS), potentiodynamic polarization) and weight loss measurements. Inhibition efficiency (E%) increased with phosphonate concentration. Adsorption of inhibitors on the steel surface in 1 M HCl follows the Langmuir isotherm model. EIS measurements showed that the dissolution process of steel occurred under activation control. Polarization curves indicated that inhibitors tested acted as cathodic inhibitors. The temperature effect on the corrosion behavior of steel in 1 M HCl without and with the inhibitor was studied in the temperature range from 313 to 353 K. The adsorption free energy and activation parameters for the steel dissolution reaction in the presence of phosphonates were determined.     

INHIBITION OF MILD STEEL CORROSION IN H2SO4 USING EXUDATE GUM FROM PACHYLOBUS EDULIS AND SYNERGISTIC POTASSIUM HALIDE ADDITIVES

The corrosion inhibitive effects of Pachylobus edulis exudate gum for mild steel in 2 M H₂SO₄ and influence of potassium halide additives on the inhibition efficiency were investigated using hydrogen evolution and thermometric methods at 30°–60°C. Inhibition efficiency was determined by comparing the corrosion rates in the absence and presence of additives. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition. It was found that the exudate gum acts as an inhibitor for acid-induced corrosion of mild steel. Inhibition efficiency (%I) of the exudate gum increased with an increase in concentration of the exudate gum and synergistically increased on addition of potassium halides but decreased with increase in temperature. Inhibitor adsorption characteristics were approximated by Temkin adsorption isotherm at all the concentrations and temperatures studied. The phenomenon of physical adsorption is proposed from the activation parameters obtained.     

CHAMOMILE (Matricaria recutita) EXTRACT AS A CORROSION INHIBITOR FOR MILD STEEL IN HYDROCHLORIC ACID SOLUTION

The corrosion inhibition of mild steel in hydrochloric acid solution by chamomile (Matricaria recutita) extract (CE) was investigated through electrochemical (polarization, EIS) and surface analysis (optical microscopy/AFM/SEM) techniques. The effects of inhibitor concentration, temperature, and pH were evaluated. Thermodynamic parameters were calculated and adsorption studies were carried out. Finally, the surface morphology was investigated. The electrochemical studies showed that CE acts as a mixed-type corrosion inhibitor with predominantly anodic behavior. CE was adsorbed physically on the metal surface and obeyed the Langmuir adsorption isotherm. It impeded the corrosion processes by changing the activation energy. In the presence of CE, the metal surface was more uniform than the surface in the absence of inhibitor. Maximum inhibition efficiency (IE) was 93.28%, which was obtained at 22°C in 7.2 g/L of inhibitor in 1 M HCl solution.     

INHIBITION OF CORROSION OF CAST IRON BY NITRITE,HYDROGEN PHOSPHATE,AND MOLYBDATE IONS IN CORROSIVE WATER

The inhibitive action of nitrite, hydrogen phosphate, and molybdate ions at various concentrations on cast iron under different experimental conditions like period of immersion, temperature, and flow velocities in corrosive water were studied by weight loss and electrochemical methods. Molybdate ions show a maximum inhibition efficiency relative to other inhibitors. The plot of log θ/1???θ versus log C is a straight line, which shows that the inhibitor obey the Langmuir adsorption's isotherm. Thermodynamic parameters like activation energy, heat of adsorption, free energy of adsorption, and entropy of adsorption were computed along with the kinetic parameters like open circuit potential (OCP), corrosion current (I_corr), Tafel slopes (β_c, β_a), Tafel constant (β) and corrosion rate.     

碳钢在高温高纯水中腐蚀与成膜规律研究

本文从理论上分析了碳钢在高温高纯水中的腐蚀机理,推导了碳钢在高温高纯水中的腐蚀与成膜规律。并用失重法等实验验证了这一规律的存在。本文还应用表面测试技术,研究了碳钢表面膜组成的变化规律。结果对了解碳钢——水热管的内部腐蚀规律、制定解决碳钢——水热管相容性措施提供了依据。     

SYNERGISTIC EFFECT OF N,N-BIS(PHOSPHONOMETHYL) GLYCINE AND ZINC IONS IN CORROSION CONTROL OF CARBON STEEL IN COOLING WATER SYSTEMS

A protective film has been developed on the surface of carbon steel in low chloride aqueous environment using a synergistic mixture of an environmentally friendly phosphonic acid, N,N-bis(phosphonomethyl) glycine (BPMG), and zinc ions. Impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the chosen environment. Potentiodynamic polarization studies showed that the inhibitor is a mixed inhibitor. X-ray photoelectron spectroscopic analysis (XPS) of the film showed the presence of the elements iron, phosphorus, nitrogen, oxygen, carbon, and zinc. Deconvolution spectra of these elements in the surface film showed the presence of oxides/hydroxides of iron(III), Zn(OH)₂, and [Zn(II)-BPMG] complex. This inference is further supported by the reflection absorption Fourier transform infrared spectrum of the surface film. Analysis by SEM is presented for both the corroded and protected metal surfaces. Based on all these results, a plausible mechanism of corrosion inhibition is proposed.     

SURFACE ANALYSIS OF INHIBITOR FILMS FORMED BY N-(2-HYDROXYBENZILIDENE) THIOSEMICARBAZIDE ON CARBON STEEL IN ACIDIC MEDIA

The corrosion and behavior of carbon steel in 2 M HCl in the presence of N-(2-hydroxybenzilidene) thiosemicarbazide (HBTC) was investigated using weight loss and electrochemical studies. The morphology of carbon steel surface was investigated using scanning electron microscopy (SEM) and Mössbauer spectrometry. The corrosion current was determined using Tafel polarization. The inhibition efficiency increased with HBTC concentration; the experimental results suggest that the presence of HBTC in the solution increases the surface coverage (θ); a decrease in the corrosion spot with the increase of the HBTC concentration indicates good adsorbability of HBTC on the metal surface. The adsorption of this compound on the metal surface is found to obey Langmuir's adsorption isotherm. Mössbauer spectroscopy showed at this stage the main product of corrosion is a non-stoichiometric amorphous Fe³⁺ oxyhydroxide, consisting of a mixture of α, β, and γ-FeOOH, where γ-FeOOH is the main phase.