In thermal power plants, coal fired boilers are commonly used due to its low cost. However, the premature failure of boiler parts is a common problem. These boilers mostly fail during operation due to oxidation, corrosion and E-C at high temperature and lead to big economic losses. The hot corrosion and erosion-corrosion alone has been reported to be responsible for 50% to 75% of entire arrest time in such applications and leads to multi-million dollar loss to the power generating industries. This problem should be addressed by the researchers. Hence, this book provides in depth review of high temperature materials, material degradation, high temperature oxidation, corrosion, erosion-corrosion & their protective measures. These protective methods include: proper selection of material, potential change of metal, corrosion inhibitors, change of environment and coating.