The present work discusses the effect of structure and morphology of rust on the corrosion behavior of a mild steel and an interstitial free steel exposed to open atmosphere for 2 years involving extreme weather conditions, where temperature varies from 2-3 to 45 °C, rainfall varies from 10 to 320 mm and humidity varies from ~ 20 to 75%. Effect of duration of atmospheric exposure, change in morphological characteristics of rust, and atmospheric parameters, such as temperature, humidity, rain and SO2 content on the corrosion behavior of both the steels was analyzed. Corrosion resistance of the interstitial free steel was better than the mild steel due to lower carbon content and better compactness of the rusts formed on the interstitial free steel.