Abstract The paper examines the effects of high temperature corrosion of the surfaces of heat exchange due to corrosive components formed in the co-combustion of biomass and coal. High temperature corrosion of the surfaces of heat exchange becomes a priority in the combustion of biomass with high chlorine and alkali metals, as alkali chlorides formed deposited on the surfaces of heat transfer, leading to serious consequences for them. Forms of manifestation of corrosion are numerous, the most important being: pitting corrosion (point), inter-granular corrosion, crevice corrosion, selective and uneven. One of the most important limitations to the use of biomass for energy purposes is the increased corrosion of the surfaces of heat exchange.