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In this study, the inhibition effect of dipotassium hydrogen phosphate (DKP) on the corrosion behavior of carbon steel ASTM A106 in a temperature range between 25 and 55 °C and an inhibitor concentration range between 7 and 23 mM in 1 mM sodium chloride solution was studied by using the potentiodynamic polarization method. As the temperature rises from 25 to 35 °C, the corrosion current density increases from 30 to 120 μA /cm2. Interaction between the inhibitor concentration and solution temperature showed that with an increase in temperature, the system will be passivated at higher concentrations of inhibitor. Adsorption mechanism of DKP was investigated by the help of thermodynamic parameters. By addition of 7 mM DKP into the solution, the value of activation energy (Ea) decreased from 82 to 50 kJ/mol. This reduction in the presence of inhibitor indicates the chemical adsorption of inhibitor on carbon steel surface. In addition, results showed that the inhibitor is more efficient at higher temperatures e.g. when the solution temperature increases from 25 to 35 °C at a concentration of 7 mM DKP, the inhibitor efficiency increases from 33 to 67 percent. The electrochemical observations were confirmed by scanning electron microscopy (SEM) and X-ray spectroscopy (EDS).

Keywords: Corrosion inhibitor, Dipotassium hydrogen phosphate, Potentiodynamic polarization, Activation energy

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