The influence of water vapor on the oxidation of copper at intermediate temperatures

The oxidation rate of high-purity Cu has been measured by means of thermogravimetry in oxygen in the pressure range 1 x 10(-4) to 1 atm and water vapor in the pressure range 3 x 10(-5) to 0.022 atm at 500 degreesC, respectively, and as a function of temperature under wet (0.022 atm H2O) and dry (3 x 10(-5) atm H2O) conditions from 400 to 1000 degreesC. The oxidation is parabolic and the rate increases with increasing water vapor pressure below 700 degreesC. The oxide scale consists of two phases, an outer CuO and an inner Cu2O phase. To distinguish between effects of the reaction conditions on the two Cu oxides, the Wagnerian rate constants of the individual Cu oxides have been deconvoluted from the gravimetric rate constant. The functional pressure dependences of the parabolic rate constants are discussed in terms of derived relations between the Wagnerian rate constants and potential prevailing point defects. (C) 2001 The Electrochemical Society.