Some ash particles in solid wastes adhere on the heat exchanger tube surfaces inside incinerators. The ash deposition may cause such troubles, heat transfer inhibition, operational problems and high temperature corrosion. The authors have conducted the fundamental research for a surface treatment technology, using a thermal spray coating technique to reduce the deposition and the corrosion. First, this paper reviewed the previous studies on the deposition and the corrosion, such as characteristics of wastes, formation of ash and mechanisms in the incinerators. Then, the corrosion mechanisms were reported by means of our analysis and thermo-equilibrium calculations of the interfaces between the tube surface and the deposition. Moreover, the recent countermeasures against the ash deposition and the hot corrosion were reviewed, and their effectiveness and feasibilities were evaluated.