No abstract

No abstract

No abstract

This research illustrates a spatially distributed cellular automaton aimed at simulating the pitting corrosion process in stainless steels. The cellular automaton model is based on the metal surface discretization into square cells; in any instant, each cell is found to be in one of the following states: (i) passivity (the passive fi lm on the cell surface is stable and protective), (ii) metastability (the passive fi lm is unstable and can either break, causing pitting initiation, or repassivate), and (iii) pitting (the cell has turned into a stable attack area, with no repassivation chance). At the very beginning, all cells are in passivity state. Subsequently, a stochastic process drives the changes in the state of cells, following rules drawn from the kinetics of pitting localized corrosion. In particular, the transition probabilities of each single cell from one state to another are infl uenced by the adjacent cells. The comparison between simulations run with the proposed model and laboratory experimental results demonstrates that the model is suitable for describing pitting corrosion processes.

An investigation of the M23C6 carbide (M = metal atom) precipitation induced by aging in AISI 304 stainless steel was performed with techniques of small‐angle neutron scattering (SANS) and transmission electron microscopy (TEM). The samples were aged at 873 and 923 K for different times after a solution treatment at 1323 K. The coherent neutron scattering length density for each sample was calculated from the chemical composition. As the carbide composition is dependent on aging time exact chemical compositions for each sample were determined with X‐ray fluorescence techniques. Coherent scattering cross‐section curves were obtained for the different aged samples, from which the total surface and total volume of precipitates per unit volume of sample were determined as a function of aging time at both temperatures. Moreover, the size distribution function of M23C6 carbide was obtained for each aging time. In general, the results obtained, taking into account the difficulty of the problem, are in satisfactory agreement with the localized TEM observations.