Rate of oxidation of typical nonferrous metals as determined by interference colors of oxide films

Abstract

By use of interference colors, investigation has been made of the variation of thickness of the oxide film on steels with temperature and time. The rate of oxidation varies as a high power of the absolute temperature. If, over short intervals, the oxidation time at constant temperature is assumed to vary as a power of the film thickness, the exponent decreases from 100 or more for thin films to about 2 for thick films. The film thickness, for constant oxidation time, increases rapidly with the absolute temperature. If, over short intervals, the thickness is assumed to vary as a power of the absolute temperature, the exponent increases with increase in film thickness, from 1 or less to about 20 or 25. The accelerating influence of temperature thus predominates over the retarding influence of increase in film thickness. Various steels are compared, with reference to resistance to oxidation, and the influence of alloying elements is discussed.