MATHEMATICS OF OXIDATION

The mathematics of oxidation kinetics involves diffusion and migration mass transfer. According to Pick s first law of diffusion, the molar flux is related to the rate of oxide thickness growth (dx/dt) is given by 

Cx = Concentration of the diffusing spedes ions/cm ) X = Thickness of the oxide scale (on or nm) 

Integrating eq. (10.14) yields what is known as the parabolic equation for 

In oxidation at high temperatures, most variables are temperature dependent. Thus, it is reasonable to assume that both diffusivity and parabolic rate constant obey the Arrhenius relationship (see Chapter 3) 

the oxide thickness becomes x = f(T). It is known that the oxide kinetics of many metals and alloys show parabolic behavior. However, other type of behavior is possible and eq. (10.12) is generalized and modeled as an empirical relationship given by 

---