Predicting Localized Corrosion in Seawater

Abstract

A number of alloys, including stainless steels, aluminum, and nickel-based alloys, are used in seawater for various applications. The localized corrosion of these materials is affected, among other factors, by temperature, microbial activity, chlorination, and flow rate. A predictive model, based on the calculation of repassivation and corrosion potentials, is presented and compared to field experiences of these alloys in seawater systems. An empirical model is used for calculating the repassivation potential of these alloys as a function of seawater composition. A mechanistic model is used for calculating the corrosion potential as a function of oxygen and chlorine concentrations. The parameters for the corrosion potential are derived from tests in flowing natural seawater or synthetic seawater. The model calculations agree with the relative ranking of these alloys in seawater. Limitations of the current model and improvements are suggested.