Steps Towards Atmospheric Corrosion Modelling

Abstract

Corrosion modeling has been done for several years aiming to provide practical information to corrosion engineers in view of lifetime predictions. The first atmospheric corrosion models were based on fitted correlations with limited or no physical background. Today the increased knowledge on corrosion mechanisms allows to take into account important aspects that govern atmospheric corrosion: composition of electrolyte and electrode composition, galvanic coupling of different materials, oxygen access and film thickness variation. In this contribution we give an overview of available models and modeling approaches. We start with models that only consider current density distributions due to competing reactions (e.g. oxygen reduction/metal oxidation) or galvanic coupling. They are particularly important for large-scale corrosion systems. Then models that consider transport of ions are presented. They are mainly research tools to obtain quantified mechanistic understand. Particular attention is given to thin water films with varying thickness that influence considerably oxygen transport and distributions of reaction products. The application is related to steel and metallic coatings coupled in several geometrical configurations (scratch, cut edge). Finally it will be explained how we see an integration of these models together with film-variation models to stepwise improve atmospheric corrosion models.