Abdul Shaban

Polynomial model of the inhibition mechanism of thiourea derivatives

Interaction of corrosion inhibitors with metal surfaces in acidic solutions was modelled by using a polynomial model based on the Langmuir adsorption isotherm. The curve-fitting procedure yielded a regression equation with a multiple correlation coefficient equal to 0.982.

Corrosion inhibition by 1-hydroxy-ethane-1,1-diphosphonic acid : an electrochemical impedance spectroscopy study

Impedance spectra of carbon steel in the presence of 1-hydroxy-ethane-1,1-diphosphonic acid (HEDP) has been investigated in neutral solutions. The aim of the measurements was to study the effect of HEDP on the carbon steel corrosion as a function of inhibitor concentration. An optimal inhibitor concentration was found. A two-time constant equivalent circuit model including a constant phase element was consistent with experimental data in the frequency range studied. The system parameters, obtained by a nonlinear fit procedure are discussed in terms of the model used. Inhibitor efficiencies derived from impedance data are compared with those obtained from polarization and weight loss measurements. Results of these investigations show that a low concentrations, HEDP inhibits carbon steel corrosion by a precipitation mechanism forming insoluble iron complexes and repairing the porous oxide layer formed n the metal surface. Increasing HEDP concentration beyond the optimal value decreases its inhibition efficiency due to the dissolution of the oxide layer.

Influence of cations on the corrosion inhibition efficiency of aminophosphonic acid

Abstract The iron/electrolyte interphase has been studied in the presence of N , N -di(phosphonomethyl)glycine (DPMG) inhibitor with or without the bivalent cations. In electrochemical measurements, inhibition was assumed by the formation of a complex in the presence of DPMG. In situ atomic force microscopy provided direct insight into changes in the surface morphology at several hundred nanometres when topographical changes owing to the breakdown of the passive layer, and initiation of corrosion were monitored. Section analysis has revealed the degree of deterioration. Bivalent cations (Ba 2+ , Sr 2+ , Ca 2+ and Zn 2+ ) synergically improved the activity of DPMG, though the mechanism was different. Barium, strontium and calcium ions in blends hindered the anodic iron dissolution, while zinc ions influenced both the anodic and cathodic processes. Composition of the surface layer was analysed by X-ray photoelectron spectroscopy (XPS). The 2:1 Ba 2+ /Sr 2+ /Ca 2+ /DPMG molar ratio in the solution resulted in a surface layer with a composition of about 1.3:1 of cation/DPMG. In the case of Zn 2+ /DPMG mixture the surface layer was composed of a mixture of slightly soluble Zn 2+ /DPMG (∼3:l) and zinc hydroxide.

An investigation of copper corrosion inhibition in chloride solutions by benzo-hydroxamic acids

Benzo-hydroxamic acids (BHA) are investigated as potential copper corrosion inhibitors in chloride solution. The BHAs investigated were: p-chloro-benzo-hydroxamic (p-Cl-BHA), o-chloro-benzo-hydroxamic acid (o-Cl-BHA), P-nitro-benzo-hydroxamic acid (p-N-BHA) and o-methyl-benzo-hydroxamic acid (o-M-BHA). Electrochemical measurements, potentiostatic polarization and ac impedance spectroscopy were carried out to evaluate the inhibition effect of the investigated BHAs. An Electrochemical Quartz Crystal Microbalance (ECQM) was used to measure electrode corrosion and inhibitor adsorption or layer formation processes. A poorly soluble layer consisting of the inhibitor and copper corrosion products is proposed to account for the protective effect in chloride solutions.

New inhibitors for copper corrosion

The study of the effectiveness of several potential copper corrosion inhibitors in acidic media was studied. The investigated thiazole derivative functional groups contain heterocyclic atoms such as nitrogen, sulfur, and oxygen. Thiazole derivatives, 5-benzylidene-2,4-dioxotetrahydro-1,3-thiazole (BDT) 5-(4¢-isopropylbenzylidene)-2,4-dioxotetrahydro-1,3-thiazole (IPBDT), 5-(3¢-thenylidene)-2,4-dioxotetrahydro-1,3-thiazole (TDT), and 5-(3¢,4¢-dimetoxybenzylidene)-2,4-dioxotetrahydro-1,3-thiazole (MBDT) were tested for copper corrosion inhibition properties. The electrolyte solution was 0.1 M Na2SO4. In situ information on corrosion and inhibition processes can be obtained using different techniques. Electrochemical measurements (EIS), in situ scanning probe microscopy (SPM), in addition to quartz crystal microbalance (QCM) measurements were applied. Those methods are very useful owing to their high sensitivity and resolution. Dynamic STM and AFM measurements on Cu(111) single-crystal electrode with and without the addition of some inhibitors were performed. The presence of the isopropyl group in the case of IPBDT produced far better protection against copper corrosion in acidic sulfate-containing media than the rest of the derivatives.

EQCM study of copper and iron corrosion inhibition in presence of organic inhibitors and biocides

Attention has been devoted to the application of quartz crystal microbalance (QCM) in the field of corrosion and corrosion inhibition. In-situ measurements were performed on copper and iron surfaces. Copper corrosion inhibition by the application of several inhibitors was followed by QCM. Copper corrosion inhibition in different electrolyte solutions such as acidic sodium sulphate and neutral sodium chloride were investigated. Different inhibitor compounds were tested for protection against copper corrosion. Three different groups of inhibitors were investigated; aromatic sulfoxides, benzo-hydroxamic acid derivatives, and azole derivatives. Among the tested sulfoxides, di-benzyl-sulfoxide (DBSO) produced the best protection, while p-chloro-benzo-hydroxamic acid showed excellent protection among the benzo-hydroxamic acid derivatives. Among the tested azole derivatives, 5-mercapto-1-phenyl-tetrazole (5-McPhTT) and 5-(4′-isopropylbenzylidene)-2,4-dioxotetrahydro-1,3-thiazole (5-IPBDT) showed excellent inhibition properties against copper corrosion in acidic media. The effect of biocides, namely N-hydroxyalkylated amino acids, on biofilm formation has been investigated, too. From the attained results, it is clear that QCM is an essential tool for obtaining important information on corrosion inhibition and its mechanism.

Corrosion Inhibitors: Quantitative Structure-Activity Relationships*

Quantitative structure–activity relationships (QSAR) between corrosion inhibition efficiency and molecular structure may help promote the discovery of new, more efficient corrosion inhibitors. In this work various methods used in the QSAR studies of corrosion inhibitors are reviewed and discussed briefly.

Investigation of copper corrosion inhibition by STM and EQCM techniques

The mechanism of copper corrosion and its inhibition were studied using electrochemical techniques, in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM) methods. The morphological changes of Cu (111) were followed in 0.1 M Na2SO4 solution at pH 2.95. The adsorption of 5-mercapto-1-phenyl-tetrazole (5-McPhTT) at different concentrations was studied. The anodic dissolution of copper in 0.1 M Na2SO4 was clearly modified and hindered by the addition of 5-McPhTT. The anodic current density was reduced sharply due to the adsorption of the inhibitor on the metal surface thus providing protection. EQCM data revealed that the addition of the inhibitor to the aggressive solution did not cause a continuous increase in the electrode mass. This fact indicates that the inhibitor effect in hindering copper corrosion was due to the adsorption of a monolayer or even a submonolayer.

Inhibition mechanism of carbon steel in neutral solution by N-phosphono-methyl-glycine

Abstract Corrosion inhibition of carbon steel in neutral aqueous solutions by N -phosphono-methylglycine (NPMG) is based mainly on the formation of an inhibiting film that protects the base metal. In order to understand the structure and composition, the layers formed on carbon steel were sputtered by an argon beam to obtain a depth profile using Auger electron spectroscopy (AES). The influence of changes in the water composition using model solutions (with and without calcium) in contact with carbon steel on the formation and growth rate of the film was studied. In addition, the effect of several factors such as time of contact and the addition of some cations, such as Ca 2+ and Zn 2+ , on the formation and composition of the inhibiting films was investigated. In addition to surface analysis, weight loss method was used to optimize and characterize the inhibitor efficiency and the effect of synergism.

Adsorption and corrosion protection behavior of thiazole derivatives on copper surfaces

Abstract The inhibition characteristics of some thiazole derivatives against copper corrosion in acidic sulphate containing media have been investigated. The investigated thiazole derivatives were 5-benzylidene-2,4-dioxotetrahydro-1,3-thiazole (C 10 O 2 H 7 SN) and 5-(4′-isopropylbenzylidene)-2,4-dioxotetrahydro-1,3-thiazole (C 13 O 2 H 13 SN). In situ information on corrosion and inhibition processes at nanoscale range were obtained using scanning tunneling microscopy (STM) in combination with quartz crystal microbalance (QCM) measurements. XPS measurements were also performed to analyze the copper electrode surface. Based on these findings the role of molecular structure in corrosion inhibition has been discussed. The presence of the isopropyl group in the 5-IPBDT molecule produced far better protection against copper corrosion in acidic sulphate containing media than 5-BDT.