Decomposition Characteristics of Humic Acid in Boiler Make-Up Water and Corrosion Effects of Its Products on Steam Turbine Blades

The decomposition characteristics of humic acid (HA) in 350°C simulated boiler make-up water were evaluated by an ion chromatograph and a total organic carbon analyzer. The corrosion behavior of steam turbine blade materials in simulated early condensate water with low molecular weight organic acids and impurity ions was studied by polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive x-ray spectrometry, and x-ray diffraction. The results showed that the anions produced by the high-temperature decomposition of HA are Cl−, , , and F−. These four impurity ions present in simulated early condensate water all promoted corrosion of 1Cr13 steel, with corrosion severity increasing with their concentration. Among these, F− exhibited the weakest corrosion effect on 1Cr13 steel, as the formation of a dense CaF2 layer inhibited corrosion of the 1Cr13 steel substrate. In this paper, the effect of decomposition products of HA in simulated boiler water on the corrosion behavior of turbine blade materials was investigated for the first time. These findings can provide guidance for monitoring indicators for boiler make-up water, thereby helping to ensure the safe operation of steam turbines.