Takahiro Nakane, Li-Bin Niu, Shuji Oishi and Hiroshi Takaku
Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University, Nagano 380-8553
The influence of formic and acetic acids on the corrosion behavior in the simulated all volatile treatment (AVT) waters at pH9.5 is investigated by electrochemical and immersion corrosion tests for boiler tube steels of STB410 carbon steel, STBA24 low- alloy steel and SUS304 stainless steel used in thermal power plants. For STB410 and STBA24 steels, the pitting corrosion susceptibilities are lowered by adding formic acid (HCOOH) and acetic acid (CH3COOH) into the simulated AVT waters added also with chloride ions (Cl-). It is suggested that both these organic acids, coexisted with Cl- ions in the water, will act as inhibitors for corrosion protection of the carbon and low-alloy steels. On the other hand, almost no inhibiting effect of both these organic acids on the corrosion behavior of SUS304 steel is observed, due to the formation of thin and tight passive films containing chromium.
boiler tube steel, corrosion, chloride ion, organic acid, all volatile treatment, thermal power plant
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