Corrosion Behavior of Reinforcing Steel in Concrete Elements in Alkaline Medium

Corrosion of steel in reinforcement concrete is complex. When chloride ions and oxygen reach reinforcing steel, corrosion is initiated. The deterioration process starts with expansions of the bare steel substrate then after cracks in the concrete are developed. The aim of this work is to determine firstly, through the electrochemical technic, the critical concentration of chloride ions which are responsible for the initiation of the dissolution step. Then, the effect of the external parameters on the rate of penetration of the chloride ions into the concrete are also evaluated. For this propose, the electrochemical behavior of the steel of construction “E24” is studied in carbonate medium without and with different concentrations of chloride ions. The effect of various parameters such as temperature, ions concentration and solution pH was also evaluated through the evolution of the open circuit potential, d.c polarization measurement and electrochemical impedance spectroscopy. The d.c polarization and EIS results shows that the addition of 0.5M CaCl2 (as critical concentration) to the saturated Ca(OH)2 solution, brings to a rapid and a continuous dissolution of the substrate where after 3 hours of immersion time the whole surface of the substrate was covered the corrosion products. This is may be due to specific adsorption of Cl-

Effect of the pH of the electrolyte on the formation and on the corrosion properties of ceria based coating on carbon steel

International audienceThe effects of the modification of the pH in 0.1M cerium nitrate solutions in the elaboration and corrosion resistance of ceria based coatings on carbon steel are investigated. Increasing the concentration of acetic acid impedes an efficient electrodeposition. At low concentrations, acetic acid seems to prevent the precipitation of Ce(OH)3 and the formation of even films of cerium oxides is favoured. The increase of pH through the addition of NaOH to the cerium nitrate solutions with 0.008M of acetic acid is shown to provide superior corrosion resistance for exposures in air and immersed in 0.5M NaCl for 30 days

Effect of the temperature of cerium nitrate–NaCl solution on corrosion inhibition of mild steel

International audienceIn this work, the effect of temperature on corrosion inhibition was studied in the absence and presence an optimal concentration of cerium nitrate (600 mg.L-1) as an inhibitor of mild steel in sodium chloride. Corrosion tests were carried out through electrochemical techniques such as impedance spectroscopy and d.c polarization measurements. The surface morphology of the films was investigated by optical microscopy (MO), white light interferometry (WLI) and a scanning electronic microscopy (SEM) coupled to EDS analysis for chemical composition. The results obtained show that the activation energy for the corrosion inhibition process to occur increased in the presence of cerium nitrate inhibitor. However, the corrosion resistance of mild steel was somewhat lost with increasing the solution temperature up to 55 °C, which lead to more cracked films. The enthalpy and entropy values suggested a mixed mechanism of chemisorption and physisorption inihibition, with a major dominant of physisorption control