The inhibition of copper corrosion by Helichrysum italicum extract (HI) in simulated acid rain was investigated using electrochemical techniques. Results indicate an increase in corrosion inhibition efficiency with the HI extract concentration. The inhibitive process was assumed to occur via adsorption of the extract on the metal surface. The thermodynamic data indicated physical adsorption and followed the Freundlich isotherm. The effect of temperature on the copper corrosion was studied. The value of the activation energy confirmed physisorption of extract molecules on the copper surface. The concentration of Cu ions released into solution, measured by atomic absorption spectrometry, was in accordance with the electrochemical results.

The adsorption and corrosion inhibition of alkanethiols self-assembled monolayer on the copper surface in simulated acid rain were investigated by electrochemical techniques. Self-assembled monolayer (SAM) was formed by 1-octanethiol (OT), 1-dodecanethiol (DT) and 1-octadecanethiol (ODT) molecules on copper surface. The experimental results showed that inhibiton efficiency increases simultaneously with increase of concentration and chain length of thiols. At the concentration of 0.5 mmol L ─1 , 1-octadecanethiol (ODT) acts as effective corrosion inhibitor with inhibition efficiency of ~ 90%. The adsorption of alkanethiol self-assembled monolayer on the copper surface was investigated by polarization measurements. The adsorption of SAMs on the copper surface followed Langmuir isotherm and the standard Gibbs energy indicated that the adsorption mechanism of OT, DT and ODT on copper is the hybrid type of physical and chemical adsorption. Values of Gibbs energy ranging from ─24 kJ mol ─1 for OT to ─32 kJ mol ─1 for ODT indicate that the chemisorption part in the adsorption mechanism prevails with the increase of alkanethiols chain length.

Abstract The effect of Satureja montana L. extract (SM) and phenolic fraction of Satureja montana L. (PF) on the corrosion behaviour of iron in 0.1 mol L-1 sodium chloride solution was studied by electrochemical techniques, UV/Vis spectrophotometry and atomic absorption spectrometry. The results of all techniques showed that SM and PF contributed to iron corrosion inhibition. The calculated inhibition efficiency values were about 45% for SM and 55% for PF. Results indicate that the inhibitive action occurs via a precipitation of the Fe-complex onto the iron surface which resulting in a decrease of the passive current density. The atomic absorption spectrometry (AAS) method was applied to the quantitative determination of iron in solution. The obtained results demonstrated good agreement with results obtained by electrochemical techniques.

The aqueous extract of the Helichrysum italicum leaves (HI) is tested as a corrosion inhibitor of an iron in a simulated acid rain using potentiodynamic polarisation, cyclic voltammetry and electrochemical impedance spectroscopy. Results of all electrochemical methods indicate an increase of a corrosion inhibition efficiency of the iron with the HI extract concentration. Maximum inhibition efficiency (~ 50 %) is obtained at 2.0 g L–1 HI extract. The inhibitive action is assumed to occur via an adsorption of the HI extract on the iron surface. Results indicate that the adsorption process is spontaneous and follows the Freundlich adsorption isotherm. According to the calculated ΔG value (~ 15 kJ mol–1), the corrosion inhibition of the iron occurs predominantly via a physisorption of the HI extract. The concentration of iron ions released into a solution, measured by atomic absorption spectrometry, is in accordance with the electrochemical results.

Abstract The growth mechanism and properties of the oxide films on iron and AISI 304 stainless steel were studied in simulated acid rain (pH 4.5) by means of electrochemical techniques and atomic absorption spectrometry. The layer-pore resistance model was applied to explain a potentiodynamic formation of surface oxides. It was found that the growth of the oxide film on iron takes place by the low-field migration mechanism, while that on the stainless steel takes place by the high-field mechanism. Kinetic parameters were determined. Impedance measurements revealed that Fe surface film has no protective properties at the open circuit potential, while the resistance of stainless steel oxide film is very high. The concentration of the metallic ions released into solution and measured by atomic absorption spectroscopy was in accordance with the results obtained from the electrochemical techniques.

Abstract The growth mechanism and electrochemical properties of an oxide film on AISI 304 grade stainless steel were studied in 0.01 and 0.1 mol L−1 fluoride solutions with different pH values (4.5, 5.5, 6.5) by means of electrochemical techniques. The anodic growth and stability of the oxide film on the stainless steel were characterized using cyclic voltammetry. Potentiodynamic analysis suggests that the oxide film growth occurs according to the high-field mechanism. Electric field strength, high-field growth exponential law constants, ionic conductivity through the film and half jump distance were determined. The electrochemical properties of the oxide film, formed spontaneously at the open circuit potential, were studied using electrochemical impedance spectroscopy. The results showed that the fluoride concentration has more considerable influence on the dissolution rate and the resistance of the oxide film than the pH.