3D cellular automata simulations of intra and intergranular corrosion

Abstract

A simple mode! for the effect of intergranular corrosion on overall corrosion processes is investigated using a cellular automata approach. The corroding polycrystalline material consists of domains and their boundaries. The domains represent the monocrystalline cores while their boundaries represent the inter granular defects. Either, a periodic pattern or randomly generated domains of Voronoï tessellation are used to represent the polycrystalline structure. The parameters of the mode!, taking into account the polycrystalline aspect of corrosion, are the domain density and the corrosion probabilities of metal grain core and grain boundary sites. The corrosion probability for grain boundary is set to a value higher than it is for the grain core. A complex surface structure appears with a high geometrical roughness when defects are not too dense. A strong correlation is established between the roughness evolution, the metal crystalline properties and the corrosion mechanism ofmetal dissolution. This work concerns simulations in 3D and extends the previous work limited to 2D simulations.

Response to Cornelius Fischer referee comments on “Impact of grain size and rock composition on simulated rock weathering” by Yoni Israeli and Simon Emmanuel

“…These values are reflective of the kinetic rate of dissolution, so that 1 represents the maximum rate of dissolution and 0 represents an inert state. In our formulation, grain boundaries dissolve 1 order of magnitude more rapidly than the mineral core, which is consistent with experimental work (Lüttge et al, 2013;Emmanuel, 2014;Bray et al, 2015).…”

Modelling intergranular and transgranular micro-cracking in polycrystalline materials

“…Two-and three-dimensional polycrystalline morphologies with inter and transgranular cracking and different constitutive behaviours have been recently studied by some authors using the phase field method [29][30][31][32][33][34], which offers the advantage of modelling, with relative versatility, the evolution of interfaces representing phase transformations fronts and/or cracks within the aggregate. Three-dimensional modelling of polycrystalline cleavage by cellular automata has also been proposed [35,36].…”

Effects of porosity in a model of corrosion and passive layer growth

“…This result is consistent with the hypothesis that the defects of an oxide/hydroxide film formed on a metal are preferential points for nucleation of metastable pits [18], i.e., for the initiation of a localized rapid corrosion which is followed by repassivation. It is important to recall that other types of random disorder or surface inhomogeneity in corrosion models are also associated with an increase of roughness of corrosion fronts [32][33][34][35] or with the changes in the morphology of corrosion pits [36][37][38]. For these reasons, we believe that an improvement of the present model may be useful for a quantitative description of the phenomena related to corrosion and passivation.…”