<p>In the present work, the corrosion rate of inner-side boiler tubes was experimentally investigated by weight loss technique. Corrosion rates were evaluated as a function of NaCl concentration, temperature, and pressure. Three variables with four levels for each variable factorial experimental design (64 runs) were used for the regression process, while two variables with four levels for each variable design (16 runs) were used for the validation process. It was found that the corrosion rate increased with the increase of these variables. The maximum corrosion rate value was 6.03 g/m² day at 1000 ppm, 140 °C, and 5 bar. Two groups of models were proposed: Kinetics and mathematical models. In the first group, the kinetic-exponent model was better than the kinetic model with a higher correlation coefficient. According to the value of the exponent, the effect of NaCl concentration and temperature was higher than the pressure. In the second group, the quadratic model was better than the linear and linear with interaction model. Again, the coefficients of NaCl concentration and temperature were more significant than the pressure. In the validation process, the deviation from experimental data was observed at elevated values of temperature and NaCl concentration. The mean absolute percentage error of the kinetic-exponent model and quadratic model were 19.5% and 29.5%.</p>