Influence of halide ions on the adsorption of diphenylamine on iron in 0.5M H2SO4 solutions

Halide ions are found to enhance the inhibition performance of amines due to enhanced adsorption of amines by the adsorbed halide ions on the metal surface. In this work, the synergistic action of halide ions on the corrosion inhibition of iron in 0.5M H2SO4 by diphenylamine has been found out by electrochemical impedance and polarization methods. Analysis of impedance data has been made with equivalent circuit with constant phase angle element for calculation of double layer capacitance values. Experiments have been carried out in the concentration range of 100–1000 ppm of diphenylamine in the presence of 0.5–1.0×10−3M of halide ions. Diphenylamine is found to be a cathodic inhibitor and the inhibition efficiency of about 65% is obtained at 1000 ppm. The anodic and cathodic Tafel slopes in the presence of diphenylamine alone and with halide ions are 65±5 and 105±5mV, respectively. Diphenylamine inhibits corrosion by adsorption and the surface coverage values are increased considerably in the presence of halide ions. In the presence of iodide ions, the inhibition efficiency of diphenylamine at 100 ppm is increased to more than 90%. In the case of other halide ions, the inhibition efficiency of diphenylamine in increased to 80% at 1000 ppm. The order of synergism of halide ions is I−�Br− >Cl−. The highest synergistic effect of iodide ions is due to chemisorption with metal surface due to its larger size and ease of polarizability

Effect of cerium ions on corrosion inhibition of PANI for iron in 0.5 M H2SO4

In recent years conducting polymers such as polyaniline are used as corrosion inhibitors for metals in acids. The performance of the inhibitor can be enhanced either by the addition of halide ions or metal cations. A study has been made on the effect of addition of ceric ions on the corrosion inhibition performance of polyaniline for iron in 0.5 M H2SO4. Techniques such as electrochemical impedance spectroscopy, potentiodynamic polarization and linear polarization resistance methods have been employed to study the corrosion inhibition. The polyaniline has been used in the concentration range of 10–100 ppm and the ceric ions concentration has been maintained at 1 � 10�3 M. The inhibition efficiency of polyaniline at 10 ppm has been increased from 53 to 88% and for 50 ppm from 71 to 90% in the presence of ceric ions. The enhanced inhibition of polyaniline in presence of ceric ions is due to the higher coverage of polyaniline–cerium complex

Co-adsorption effect of polyaniline and halide ions on the corrosion of iron in 0.5 M H2SO4 solutions

The synergistic effect of halide ions on the inhibition of corrosion of iron in 0.5 M H2SO4 solutions by polyaniline has been studied by polarization and impedance methods. Addition of 0.5 · 103M I ions enhanced the inhibition efficiency of polyaniline at 10 ppm from 53% to 90%. However in the case of bromide and chloride ions, the inhibition efficiency of polyaniline at 50 ppm has been increased from 71% to 90%. The synergism parameter in all cases is found to be greater than 1. The synergistic effect is attributed to enhanced adsorption of polyaniline by the adsorbed halide ions

Influence of metal cations on the inhibitive effect of polyaniline for iron in 0.5 M H2SO4

Polyaniline and metal cations such as Zn2+ and Mn2+ ions have been found to inhibit corrosion of iron in sulphuric acid moderately. It has been reported that the metal cations are found to interact directly with polyaniline via protonation of imine nitrogen atom of quinoid groups of polyaniline and induce chemical and confirmational changes to polymer. Hence a study has been made on the inhibition of iron in 0.5 M H2So4 by polyaniline in the presence of Zn2+ and Mn2+ ions (1 * 10pow-3 M) by electrochemical impedance spectroscopy, linear polarization and tafel polarization methods. The inhibition efficiencies of polyaniline are found to be 40% for 10 ppm and 72% for 100 ppm. But in the presence of metal cations, the inhibition efficiencies of polyaniline are found to be increased to 80% for 10 ppm and more than 90% for 100 ppm. Higher inhibition efficiency of polyaniline in the presence of metal cation is attributed to the increased electron rich benzenoid groups absorb more effectively on iron surface and there by reduces the corrosion rate markedl

Corrosion Inhibition of Iron in 0.5 mol L-1 H2SO4 by Halide Ions

O efeito de inibição de íons haletos, tais como iodeto, brometo e cloreto, na corrosão de ferro em solução 0,5 mol L-1 de H2SO4, e o comportamento da adsorção desses íons na superfície do eletrodo, foram estudados pelos métodos de polarização e de impedância. Foi observada uma inibição de aproximadamente 90% para íons iodeto a 2,5 × 10-3 mol L-1 e para íons brometo a 10 × 10-3 mol L-1, e de 80% para íons cloreto a 2,5 × 10-3 mol L-1. O efeito da inibição aumenta com o aumento da concentração dos íons haletos I– e Br–, mas decresce no caso do Cl–, para concentrações maiores que 5 ×10-3 mol L-1. Os valores de capacitância de dupla camada diminuíram consideravelmente na presença dos íons haletos, o que indicou que esses ânions são adsorvidos no ferro no potencial de corrosão. The inhibition effect of halide ions such as iodide, bromide and chloride ions on the corrosion of iron in 0.5 mol L-1 H2SO4 and the adsorption behaviour of these ions on the electrode surface have been studied by polarization and impedance methods. It has been found that the inhibition of nearly 90% has been observed for iodide ions at 2.5 × 10-3 mol L-1, for bromide ions at 10 × 10-3 mol L-1 and 80% for chloride ions at 2.5 × 10-3 mol L-1. The inhibition effect is increased with increase of halide ions concentration in the case of I– and Br– ions, whereas it has decreased in the case of Cl– ion at concentrations higher than 5 × 10-3 mol L-1. The double layer capacitance values have decreased considerably in the presence of halide ions which indicate that these anions are adsorbed on iron at the corrosion potential

Investigation of the inhibitive effect of poly(diphenylamine) on corrosion of iron in 0.5 M H2SO4 solutions

In recent years, polymer amines such as polyaniline has been reported as an efficient corrosion inhibitor for iron in acid media. In this paper, the performance of poly(diphenylamine) as corrosion inhibitor for iron in 0.5 M H2SO4 has been evaluated by potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy and compared with the performance of the diphenylamine monomer. It has been found that poly(diphenylamine) is an efficient inhibitor since the maximum efficiency of 96% has been observed at very low concentration of 10 ppm where as the monomer has given an efficiency of 75% at 1000 ppm. Besides, poly(diphenylamine) has been found to improve the passivation characteristics of iron in 0.5 M H2SO4. FTIR studies have shown that the poly(diphenylamine) is strongly adsorbed on the iron surface and inhibits the corrosion effectively

Inhibition of iron corrosion in 0.5 M sulphuric acid by metal cations

Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn2+, Mn2+ and Ce4+ ions in the concentration range 1–10 � 10�3 M has been found out. The corrosion behaviour of iron in 0.5 M H2SO4 in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce4+ � Mn2+ > Zn2+