Initial Stages

SUMMARYAuger electron spectroscopy was used to examine the initial stages of oxidation of apolycrystalline copper - 19. 6-atomic-percent-aluminum alloy. The growth of the 55-eV"aluminum oxide" peak and the decay of the 59-, 62-, and 937-eV copper peaks wereexamined as functions of temperature, exposure, and pressure. Pressures ranged from1x10 -7 to 5x10 -4 torr of 0 2 . Temperatures ranged from room temperature to 7000 C.A completely aluminum oxide surface layer was obtained in all cases. Complete disap-pearance of the underlying 937-eV copper peak was obtained by heating at 7000 C in oxy-gen at 5x10 -4 torr for 1 hour. Temperature studies indicated that thermally activateddiffusion was important to the oxidation studies. The initial stages of oxidation followeda logarithmic growth curve x = x 0 In 1 + ) with a pre-logarithmic factor, x 0 , of0. 119 (thickness in arbitrary units) and a time factor, 70, of 0. 129 second.INTRODUCTIONThe formation of oxide layers for corrosion protection has long been a topic of in-terest (refs. 1 to 7). The principal objective of such studies was to fabricate alloys inwhich one component was selectively oxidized on the surface. This single component ox-ide was to be chemically inert (as, for example, aluminum oxide) and thus prevent fur-ther oxidation of the surface. The oxide surface film could have other desirable proper-ties such as prevention of hydrogen embrittlement in titanium-aluminum alloys and al-tering friction and wear behavior of surfaces.Until recently, no analytical technique has been available to identify the initialstages of oxidation of pure metal and alloy surfaces. The most frequently used tech-niques have been weight change, hot-stage X-ray diffraction, and hot-stage high-energy