The oxidn. of nickel gauze catalysts by O2 was investigated by transient response methods. Qual. description of the exptl. transient responses have shown that the oxidn. of metallic nickel proceeds in two stages. The first step is a fast dissocn. of gaseous oxygen on the catalytic surface, followed by oxygen diffusion from the surface into the bulk. This slow second step explains the long tailing obsd. from the exptl. transient responses. Furthermore, a rise of temp. was obsd. during the nickel oxidn. A kinetic model has been developed on the basis of the exptl. results in order to provide quant. information about this reaction. For nickel gauze oxidn., a non-isothermal model combining the subsurface oxygen diffusion with an exponential distribution for the activity of surface sites gave a good agreement with exptl. transient data. As a result, the activation energies and the pre-exponential factors of the rate consts. as well as the characteristic oxygen diffusion times were detd. [on SciFinder (R)]