الفهرس | Only 14 pages are availabe for public view |
Abstract In this work the electrochemical behavior of carbon steel was investigated in saline acidic, neutral and basic solutions. Conventional electrochemical techniques such as open-circuit potential measurements, polarization methods and electrochemical impedance spectroscopy (EIS) were used. Scanning electron microscope (SEM) was used to study the surface of carbon steel sample. The results have shown that the rate of corrosion in acidic solution is relatively high compared to that in neutral or basic solutions. The increase in chloride ion concentration and sulphate nearly lead to increase the corrosion rate. The impedance data were fitted to an equivalent circuit model that explains that different electrochemical processes occurring at the electrode/electrolyte interface. Also, the inhibition of corrosion of carbon steel in neutral solutions by using β-carotene and Thiourea, as environmentally safe corrosion inhibitors, was investigated. The calculated free energy of adsorption reveals that adsorption of β-carotene, β-cart., and Thiourea, TU, on the carbon steel alloy is of a physical nature, and there is no chemical interaction between the inhibitor molecules and the metallic surface. SEM image of carbon steel after immersion for 120 min in 3.5 % NaCl and in 0.6 M Na2SO4 solution revealing severe damage on the surface caused by metal dissolution, but proves that the steel surface was protected after adding 50 mg/L β-carotene inhibitor. It is observed that the surface damage has diminished compared with the blank solution |