Adsorptive stripping voltammetry (AdSV) provides fast and sensitive detection of iron in process waters of the water-steam circuit (boiler feed water, makeup water, condensate) in power plants. This is achieved by adding 2,3-dihydroxynaphthalene (DHN) as complexing agent to convert the iron into an adsorbable complex that is reduced on the electrode surface after a defined preconcentration time. Detection limits down to 0.1 μg/L can be achieved.
Image credit: Metrohm Middle East FZC
At high temperatures, steam reacts with the iron in the carbon steel of steam boilers. This leads to the formation of a thin layer of magnetite, an iron(II,III) oxide, which passivates the steel surface protecting it against further corrosion (Schikorr reaction).
Under unfavorable conditions, the inhibiting magnetite layer can flake off, which leads to elevated iron concentrations in the water-steam circuit. A regular iron determination enables monitoring of not only corrosion processes but also the formation and destruction of the protective magnetite layer.
Compared to atomic absorption spectroscopy (AAS) or inductive couple plasma (ICP) for the determination of iron, adsorptive stripping voltammetry (AdSV) is a viable, less sophisticated alternative with only a moderate investment in hardware required and low running costs. To learn more about the method read our free Application Note AN-V-179 on this analysis.