This research aims to study the reduction of air heaters corrosion in steam boilers and increasing their efficiency , by the application of combined heating of air by steam and exhaust gases. The experimental data of this research demonstrates thatheater corrosion could bereduced by maintaining the exhaust gases temperature above the dew point of sulfuric acid depending onthe amount of sulphur in the fuel oil ,by controlling air heat temperature by steam.Which increases the boiler efficiency as a consequence of reducing the fuel consumption by 9% as a maximum , reduces heat loss, minimizes maintenance costs and reduces the time of emergency shutdowns.