著者

押川 渡 篠原 正 元田 慎一

出版者

Japan Society of Corrosion Engineering

雑誌

Zairyo-to-Kankyo (ISSN:09170480)

巻号頁・発行日

vol.52, no.6, pp.293-298, 2003-06-15 (Released:2011-12-15)

参考文献数

18

被引用文献数

18 35

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To estimate concentration and thickness of water film formed on metal surface in atmospheric environment, relative humidity (RH) data in equilibrium with various concentrations of strong electrolyte solutions were calculated with available thermodynamic data. The activity coefficient of water (fw(X)) for the solution with molar fraction of water (X) could be given as a function of ionic strength of the solution, which was determined by mean activity coefficient data in literatures for electrolytes in the solution. RH values obtained as RH(%)=100×fw(X)·X were fitted well with measured values of these solutions in each literatures, for example NaCl, MgCl2, Na2SO4, Mg(NO3)2 and so on. RH values for solutions with various contents of Na-MgCl ternary system were also calculated as NaCl-MgCl2 mixed solution. The calculated RH values were also fitted well with measured data. Using the relationship between density and concentration of the solution, the thickness of water film was also calculated. When the sea salt is put on 1g/m2, while the thickness of water film reaches 3-30μm in the range of relative humidity is larger than 75%, it remains 0.3-0.7μm in the range of relative humidity is smaller than 75% where NaCl solid state deposition occurs.