Online ISSN : 1881-9664
Print ISSN : 0917-0480
Proposal of a New Stability Index Taking Account of Corrosion Inhibiting Action of Silica and Derivation of Empirical Equations Containing the New Index for Corrosiveness and Scale Formation of Water
Makoto YuasaToshiharu WakeTakashi FujiedaNobuyuki MomozawaAritomo YamaguchiYoshiaki ShibataShintaro SomeyaAkira Takahashi
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2003 Volume 52 Issue 8 Pages 408-415


A new stability index [an improved stability index (SI′)] has been proposed that introduces corrosion inhibiting ability of silica in a broad range of temperature and pH into the conventional index of the corrosive action and scale formation of water, and new empirical equations [Eqs. 1-3] that characterize water were derived using the new index. The derived SI′ was effective in the range of SI>6. The SI′ was balanced at 0, and then SI′=0 differed from SI=6. In addition, a possibility was found for prediction and inhibition of corrosion of ferrous metals based on the equations by controlling the concentration of silica ([SiO2]).
y=K0{1-exp(-3.06×10-1SI′)} (1)
K0=(2.09T+1.872×102)exp{-(-1.08×10-4T+7.62×10-3)[SiO2]} (2)
SI′=x-7.21{1-1.71×10-1exp(-8.59×10-3[SiO2])} (3)
[y: corrosion rate (V) (mdd), K0: constant affecting saturation value of corrosion rate (y) (mdd), T: temperature (°C), [SiO2]: silica concentration (mg SiO2/dm3), x: stability index (SI) (-)]

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