caa a22 4500 388076690 CHVBK 20180307125201.0 cr unu---uuuuu 161130e199907 xx s 000 0 eng 10.1557/S0883769400052672 doi S0883769400052672 pii (NATIONALLICENCE)cambridge-10.1557/S0883769400052672 In Situ X-Ray-Diffraction Studies of Passive Oxide Films [Elektronische Daten] Most metals are thermodynamically unstable in aqueous environments. They are kinetically stabilized by the formation of very thin "passive” oxide films that provide protection from corrosion. The technological importance of passive films has led to widespread investigation of their structure and chemistry. However, despite decades of work since Michael Faraday first described the existence of the passive film on iron, the atomic structure of these films is still poorly understood. This is because the films are so thin (typically only a few nanometers thick), making measurements difficult, and because the structure can only be investigated in the (wet) electrochemical environment in which these films form. The electrochemical nature of the formation of these oxide films is shown in Figure 1, which presents the current response of an iron electrode in an aqueous solution to an applied voltage (potential). As the potential is slowly increased from negative (cathodic) to positive (anodic), the iron first begins to dissolve. This area of dissolution is known as the active region, indicating that the iron is corroding freely as ferrous ions (Fe2+). Then, at a sufficiently anodic (oxidizing) voltage, a thin (30 Å) oxide film forms at the iron surface, preventing further dissolution. This results in a marked decrease in the measured current, a phenomenon known as passivity. Over the passive region, the current is virtually independent of applied voltage and remains extremely low, indicating that the iron is protected from additional oxidation or corrosion. Copyright © Materials Research Society 1999 Ryan Mary P. Toney Michael F. Davenport Alison J. Oblonsky Lucy J. MRS Bulletin Cambridge University Press 24/7(1999-07), 29-35 0883-7694 24:7<29 1999 24 MRS https://doi.org/10.1557/S0883769400052672 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1557/S0883769400052672 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ryan Mary P. NATIONALLICENCE 700 1- Toney Michael F. NATIONALLICENCE 700 1- Davenport Alison J. NATIONALLICENCE 700 1- Oblonsky Lucy J. NATIONALLICENCE 773 0- MRS Bulletin Cambridge University Press 24/7(1999-07), 29-35 0883-7694 24:7<29 1999 24 MRS CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge