This paper presents a corrosion rate model for mild steel in hydrochloric acid. A non-linear corrosion rate equation was developed, validated and used to relate the acid point, pH of hydrochloric acid as corrosive medium for mild steel to other variables like corrosion rate and substrate immersion period. The inhibitor used is Sinclair synthetic paint – an organic inhibitor. The effect of variables on corrosion rate has been investigated using non-linear regression analysis. The derived model is an exponential decay function of two input factors. The coefficient of correlation between the calculated and experimental data indicates good performance of the derived model.