Modeling ‘dry’ OCP measurements to characterize archaeological iron corrosion II: Short-time transients

Abstract

• “Dry” open circuit potential-time measurements are recorded for archaeological iron objects. • Theoretical modeling of short-time (<1 min) transients is presented. • Effective RC parameters can be evaluated from a nano-pitting corrosion model. • RC parameters provide information on the type and degree of corrosion. Short-time transients recorded in “dry” open circuit potential (OCP) measurements performed on archaeological iron artifacts are modeled based on their ascription to pitting corrosion events. Three types of short-time transients can be discerned, the two first ones yielding approximately exponential growth and decay curves apparently driven by charging/discharging processes. A third type of transients that consists of sharp rising/decay involving successive anodic and cathodic excursions over the background OCP vs. time curve is described assuming a logistic variation of charge transfer in dissolution/repassivation steps of pit evolution. Theoretical modeling is in agreement with experimental data for a set of archaeological iron objects.