Corrosion-and Electrochemical Dissolution Behavior of Cast Iron Measured with Different Electrochemical Cell Types

The corrosion behavior and the electrochemical dissolution of three different cast iron types and one high purity iron sample in NaNO3 electrolyte (25°C, 1 M, pH: 7) were investigated by comparing three different cell setups: a relatively simple beaker-cell, a small-sized capillary flow-cell and a high-current gap-cell. The electrochemical cell types differ in electrolyte flow rate, size of the measured sample surface and applied current density. The work aims at investigating the electrochemical dissolution of inclusion containing materials (cast iron) and the evolution of a strategy that allows the determination of process parameters used for the design of electrochemical machining (ECM) processes. All samples were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Electrochemical characterization was carried out by cyclic voltammetry and chronoamperometry experiments. It could be shown that the electrochemical dissolution behavior was dominated by the matrix structure and the geometry of the included graphite particles. The determination of corrosion potential and-current were mainly influenced by the electrolyte flow rate. Our new flow cell design (gap-cell) is suited for an easy and fast electrochemical characterization of materials under high current densities.