Adsorption studies of water on copper, nickel, and iron using the quartz‐crystal microbalance technique: Assessment of BET and FHH models of adsorption

Abstract

In the atmospheric corrosion of copper, nickel, and iron, the adsorption of water affects the corrosion rates. Knowledge of waler adsorption and metal oxyhydroxide formation is important in understanding the atmospheric corrosion process. The purposes of the present research were (1) to measure the adsorption of water on metal surfaces as a function of temperature and relative humidity (RH) and (2) to assess Brunauer-Emmett-Teller (BET) model and Frenkel-Halsey-Hill (FHH) model for water adsorption. ln the present research, the quartz-crystal microbalance (QCM) tcchnique was used to measure the mass changes of copper, nickel, and iron at 0 to 100 % RH and 7-90°C under nitrogen environments. Less water was adsorbed on copper, nickel, and iron which formed oxides than on gold. BET and FHH models could not fit the data points with singlc functional relationships. AHids values were calculatcd using modified BET method and they decreased with temperature. Bei der atmospharischen Korrosion von Kupfer, Nickel und Eisen beeinfluBt die Wasseradsorption die Korrosionsgcschwindigkeiten. Die Kenntnis dcr Wasseradsorption und der Rildung von Metalloxyhydroxiden ist wichtig fur das Verstandnis des atmospharischcn Korrosionsproi.esses. Der Zweck der vorliegenden Untersuchung war. (1 1 die Wasseradsorption auf Metalloberflachen als Funktion der Temperatur und der relativen Fcuchtigkeit (RH) zu messen und (2) das Brunauer-Emmett-Teller-(BET)-Modell sowie das Frenkley-Halsey-Hill-(FHH)-Modell fur die Wasseradsorption zu bcurteilcn. In der vorliegenden Arbeil wurde die Quarzkristall-Mikrowaagen-(QCM)-Technik eingcsetzt. um die Massenanderungen von Kupfer, Nickel und Eisen bei 0 bis 100% RH und 7 -90°C unter Stickstolfumgebungen zu messen. Auf Kupfer, Nickel und Eisen, die Oxide bilden, wurde wcniger Wasser adsorbiert als auf Gold. Das BET-und das FHH-Modell konnten die Datenpunkte nicht durch einfache funktionale Beziehungen anpassen. Mit Hilfe einer modifizierten BET-Methode wurden AHzd5-Werte berechnet, die mit der Temperatur abnehmen. Sungkyu 1.w Surface technology lab., Department of Metallurgy.Tne University of Tokyo 7-3-I Hongo, Bunkyo-ku,Tokyo, 113 (Japan) Roger W Sluehlr

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