The corrosion behavior of carbon steel C45 has been investigated in the absence and presence of different content of NaCl at four different temperatures 293, 303, 313, and 323 K by using potentiodynamic polarization technique. The results shown that the corrosion of carbon steel in the absence of NaCl is lower than in the presence of NaCl, and increased the concentration of NaCl lead to increase the corrosion rate at all the experimental temperatures and the maximum corrosion rate was observed in 14% NaCl. The corrosion rate was decreased after reaching the maximum value and increase the solution concentration of NaCl at 20% and 26% at all the four temperatures and that could be attributed to the high resistance of the solution when the concentration be higher. All the thermodynamic functions and activation energy are calculated and the results of Gibbs Free energy and enthalpy shown that the corrosion of carbon steel C45 in the absence or presence of NaCl at each same temperature is nonspontaneous and endothermic. The obtained results were in a good agreement with previous work based on the using of the weight loss method by another research work).
Keywords: Corrosion, Carbon steel, NaCl, Corrosion Rate, Thermodynamic Functions