Abstract
Corrosion inhibition of mild steel by adenine (AD) in 0.1 M solutions of HCl and H2SO4 was investigated using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The study was carried out at 30 °C and 60 °C respectively. The effect of iodide ions on inhibition efficiency was also assessed. Results showed that AD had a moderate inhibitive effect on the acid corrosion of mild in the order HCl > H2SO4 at 30 °C and H2SO4 > HCl at 60 °C. The presence of iodide ions in the acid media increased the efficiency of AD. From potentiodynamic polarization studies, it was observed that AD alone and the mixture of AD+KI surpressed both the anodic and cathodic partial reactions. The corrosion processes were inhibited by adsorption of AD onto the mild steel surface in a concentration and temperature-dependent manner. Langmuir isotherm was used to explain the adsorptive characteristics of AD.
Highlights
Mineral acids find extensive applications in many industries: chemical, fertilizer, steel, mineral, water, oil, food, etc. (Dillon, 1994)
The present study investigates the effect of type of acid anions on the corrosion inhibition potential of adenine in hydrochloric and sulphuric acid solutions
Results obtained from the study show that AD inhibited the corrosion of mild steel in 0.1 M solutions of HCl and H2SO4
Summary
Mineral acids find extensive applications in many industries: chemical, fertilizer, steel, mineral, water, oil, food, etc. (Dillon, 1994). The acidic properties of their ionized, aqueous solutions are due to the presence of hydrogen ion H+ and its complexed form hydronium ion H3O+. The dissolution of metals in solutions of acids is a heterogeneous electrochemical reaction. Two phases coexist - a solid and a liquid, but as the reaction starts, a third phase appears - hydrogen gas, evolving from the metal surface. Metal surfaces exposed to aqueous acidic environments are observed to undergo corrosion attack. The corrosion of mild steel in any given environment may proceed via different mechanisms and manifest in various forms. In a bid to reducing corrosion, some organic compounds called inhibitors are added to the agressive solution in contact with the metal surface thereby inhibiting corrosion and reducing the corrosion rate of the metal (Sastri, 1998)
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