Milan B. Radovanović

Inhibition of copper corrosion in acidic sulphate media by eco-friendly amino acid compound

This investigation aimed to study a “green” non-toxic biodegradable copper corrosion inhibitor in an acidic sodium sulphate solution. The methods used in the investigation of cysteine as a copper corrosion inhibitor in an acidic sodium sulphate solution were: potentiodynamic measurements, open circuit potential measurements, and chronoamperometric measurements. Optical microscopy was used in addition to electrochemical methods. Potentiodynamic measurements show that cysteine has good inhibitory properties in an acidic medium. Polarisation curves indicate that the presence of cysteine in a sulphate solution decreases the current density and that using various cysteine concentrations results in the formation of a protective film on the surface of the electrode due to the formation of the Cu(I)-cys complex. These results are confirmed by chronoamperometric measurements. Furthermore, it is clear from microphotographs that a protective film does form on copper electrode in the presence of cysteine. The Langmuir adsorption isotherm indicates that cysteine is chemisorbed on the surface of the electrode.

Influence of purine on copper behavior in neutral and alkaline sulfate solutions

The effect of purine (concentration range of 1.00 × 10−6–1.00 × 10−2 M) on the behavior of copper in a 0.5 M Na2SO4 solution (pH 7 and pH 9) was studied using the open circuit potential measurement, potentiodynamic polarization, and chronoamperometry. Potentiodynamic polarization shows that purine acts as a copper corrosion inhibitor in both alkaline and neutral sulfate solutions. The efficiency of inhibition increases as the purine concentration increases. Chronoamperometric results follow the same trend as the results of potentiodynamic polarization. The inhibition effect can also be observed visually by microscopic examination of the electrode surface. Purine is adsorbed on copper surface according to the Langmuir adsorption isotherm.

Protection of copper surface in acidic chloride solution by non-toxic thiadiazole derivative

Abstract This paper deals with electrochemical properties of copper in the presence of the non-toxic compound 2-amino- 5-ethyl- 1,3,4-thiadiazole (AETDA) in acidic chloride solution. Electrochemical techniques: open circuit potential measurements, linear potentiodynamic measurements, cyclic voltammetry measurements and chronoamperometric measurements in addition to SEM–EDS analysis were used during the work. Results show that inhibition efficiency of 2-amino-5-ethyl-1,3,4-thiadiazole depends on inhibitor concentration and immersion time of copper electrode in inhibitor solution. Cyclic voltammetry and linear potentiodynamic measurements beside chronoamperometric measurements indicate formation of protective layer on copper surface. Moreover, results obtained by electrochemical measurements point out that the stability of formed layer depends primarily on the concentration of inhibitor and of potential values at which protective film is formed. Also, potentiodynamic measurements show that AETDA in acidic chloride solutions acts as mixed-type inhibitor. Inhibition mechanism of 2-amino-5-ethyl-1,3,4-thiadiazole includes adsorption of inhibitor on active sites on electrode surface which was confirmed by SEM–EDS analysis of the electrode surface. Adsorption of the AETDA in HCl solution obeys Langmuir adsorption isotherm.

Effect of gelatine and 5-methyl-1H-benzotriazole on corrosion behaviour of copper in sulphuric acid containing Cl− ions

Abstract Copper corrosion behaviour in the presence of binary system containing 5-methyl-1H-benzotriazole and gelatine as well as 1H-benzotriazole and gelatine in 0.01 mol dm−3 H2SO4 with the addition of different concentration of Cl− ions was investigated in this study. The corrosion inhibition effect of these compounds was examined by electrochemical techniques (open circuit potential, potentiodynamic polarization and cyclic voltammetry measurements) and weight loss measurements. The surface analysis by scanning electron microscopy with energy X-ray spectroscopy was also performed to assess the morphology of untreated and treated surface of copper coupons. According to the potentiodynamic polarization results, these inhibitors showed good performance in the presence of Cl− ions and they act as mixed-type inhibitors. The inhibition efficiency of binary system is over 90% indicating that these compounds provide good copper protection in sulphate-chloride solutions. The results obtained from weight loss measurements are in good agreement with the results obtained by electrochemical measurements.

Inhibition of Brass Corrosion by 2-Mercapto-1-methylimidazole in Weakly Alkaline Solution

The electrochemical behavior of brass and anticorrosion effect of 2-mercapto-1-methylimidazole (2-MMI) in weakly alkaline solution with and without presence of chloride ions was investigated using electrochemical techniques in addition to SEM-EDS analysis. Results show that inhibition efficiency depended on inhibitor concentration and immersion time of brass electrode in inhibitor solution. Inhibition mechanism of 2-mercapto-1-methylimidazole includes adsorption of inhibitor on active sites on electrode surface which was confirmed by SEM-EDS analysis of the brass. Adsorption of the 2-MMI in sodium tetraborate solution obeys Flory-Huggins adsorption isotherm, while in the presence of chloride, ions adsorption of inhibitor obeys Langmuir adsorption isotherm.

Protection of Brass in HCl Solution by L-Cysteine and Cationic Surfactant

Electrochemical behavior of brass and inhibitory effect of L-cysteine in HCl solution are investigated using electrochemical techniques in addition to SEM-EDS analysis. Results show that inhibition efficiency depends on inhibitor concentration and immersion time of brass electrode in inhibitor solution. Electrochemical test results point to formation of Cu(I)-cysteine complex on the brass surface in chloride solutions with addition of different amounts of cysteine. The formed complex has an important role in inhibition of the corrosion process in the examined media because Cu(I)-cysteine significantly reduces dissolution of brass. Curves obtained in acidic solution in the presence of cysteine after pretreatment in sodium dodecyl sulfate (SDS) by cyclic measurements and potentiodynamic polarization measurements indicate intense inhibition of corrosion processes. Efficient inhibition of brass dissolution is result of formation of a stable protective layer on the brass surface after pretreatment of the electrode in SDS solution. The brass surface is modified in sodium dodecyl sulfate solution in order to increase cysteine adsorption on the electrode surface and to improve inhibition efficiency. Inhibition mechanism of cysteine includes adsorption on active sites on the electrode surface, which is confirmed by SEM-EDS analysis of brass. Adsorption of cysteine in hydrochloric acid solution obeys the Langmuir adsorption isotherm. Also, Gibbs free energy of adsorption has a value of −31.5 kJ/mol and indicates strong adsorption of cysteine on the electrode surface.

Compounds from the imidazole group as copper corrosion inhibitor in acidic sodium sulphate solution

To estimate influence of 2-mercapto-1-methylimidazole and 4(5)methil-imidazole on electrochemical behaviour of copper electrode in 0.5 moldm-3 Na2SO4 solution, pH 3, following methods were used: open circuit potential measurements, potentiodynamic polarization, chronoamperometry. Potentiodynamic measurements showed that investigated inhibitors can be used as copper corrosion inhibitor in acidic 0.5 moldm-3Na2SO4 solution. Increase of concentrations leads to better inhibitor efficiency. These results were confirmed using the chronoamperometry. Adsorption of 2-mercapto-1-methylimidazole and 4(5)methil-imidazole obeys Langmuir adsorption isotherm.

2-Amino-5-ethyl-1,3,4-thiadiazole as inhibitor of brass corrosion in 3% NaCl

The electrochemical behaviour of brass and anticorrosion effect of 2-amino-5- ethyl-1,3,4-thiadiazole (AETD) in chloride solution was investigated using electrochemical techniques. Results show that inhibition efficiency depended on inhibitor concentration and immersion time of brass electrode in inhibitor solution. Mechanism of brass corrosion inhibition by 2-amino-5-ethyl-1,3,4-thiadiazole includes adsorption of inhibitor on active sites on electrode surface. Adsorption of AETD in 3% NaCl solution obeys Langmuir adsorption isotherm.