Role of transport properties in corrosion product growth

The tendency for corrosion and the observed rate of corrosion are determined in large part by the transport properties of thin corrosion product layers. Both ionic and electronic transport are important. For continued corrosion, a corrosion product film capable of high ionic transport is required at the metal surface. The electronic transport properties will affect the spatial distribution of reduction reactions in the corroding system. In this paper, a generalized model for a corroding system is presented, and the relevant processes that control corrosion are identified. Four systems currently under study in our research group are diagnosed in relation to the generalized model: copper in sulfurous gases, metals in chloride solutions, bronze disease of ancient artifacts and silver in sulfurous gases.