Many lessons were learned regarding appropriate water/steam chemistry control during the prime time of coal-fired power plant operation which assisted new research to be carried out by organisations including the Electric Power Research Institute and the International Association of the Properties of Water and Steam. This article refers to historical case studies to highlight difficulties which can occur due to improper chemistry control and Metrology and Analytical Technology and discusses such issues ranging from waterwall tube failures due to corrosion and hydrogen damage to single-phase and two-phase flow accelerated corrosion and steam system damage and turbine blade corrosion.