Kinetics of oxidation of metals in the air at room temperature using EDX

The kinetics of oxidation of Zn, Cu, Ni and C. steel were studied using the surface techniques, SEM, EDX and XRD, and electrochemical impedance spectroscopy (EIS) technique. EDX results showed that the variation of weight percent oxygen (Wt% O) on the surface of the four metals with the exposure time gave the same behavior, there is an increase of Wt% O with increasing the exposure time until about 2 h followed by a plateau, then the Wt% O increases again with increasing the time of exposure than 4 h. Fitting the experimental data of the four metals to the kinetic laws of oxidation indicated that the logarithmic law was fitted in short exposure (0.5 - 4 h), however, the parabolic law was fitted in long exposure (6 - 10 h). The values of each logarithmic rate constant (kl) and parabolic rate constant (kp)for the four metals were calculated. The kinetic of oxidation of the metals under study with exposure time is confirmed utilizing XRD technique. The protective action of the air-formed oxide films was investigated by EIS technique. The electrochemical impedance spectroscopy results confirmed the EDX results.