The heat transfer from steel surfaces to boiling water is subject to irreversible negative temporal changes. In this work, the influence of the responsible physicochemical processes on the heating surface is investigated by thermotechnical measurements. Therefore, the influence of exemplary inorganic and organic feed water agents on the heat transfer, critical operating conditions and the surface properties of horizontal heating surfaces made from carbon-steel is examined thermotechnically in a special apparatus under pool boiling conditions and further characterised by analytical methods.