In modern industrial world, engineering components are prone to more rapid surface degradation such as erosion-corrosion, overheating, wear, solid particle abrasion, high temperature corrosion, etc. Due to above surface degradation, major problems causes tube wall thinning, results in premature failure of the super heater and reheater tubes. Alloys used at high temperature should possess good mechanical properties along with erosion - corrosion resistance. The present study behavior of boiler steel ASTM-SA213 T-22 (used in most of the power plants in the Northern India) has been investigated for high temperature erosion-corrosion behavior in the uncoated as well as coated condition. Detonation Gun thermal spraying process was used for coating on boiler steel. SEM/EDAX, XRD and X-ray mapping analysis done to reveal the microstructure and compositional features of boiler steel. The microstructure indicates uniform and dense coating. Thermogravimetric techniques is used to investigate the erosion-corrosion behavior at 900ºC for 1000 hours. SEM/EDAX, XRD and X-ray mapping techniques were used to analyze the corrosion products.