Protective Iron Carbonate Films—Part 1: Mechanical Removal in Single-Phase Aqueous Flow Available to Purchase

The protective role of iron carbonate films deposited on steel surfaces as by-products of carbon dioxide (CO₂) corrosion may be hindered by mechanical film removal due to hydrodynamic forces. Damage to the film is frequently accompanied by severe corrosive attack, which may ultimately result in costly equipment failure. The present work reports on experimental investigations of mechanical film removal (its kinetics and level of damage to the film) using a rotating cylinder configuration in the highly turbulent flow regime. Corrosion rate monitoring using the linear polarization resistance technique was used as a tool for implicit film removal rate measuring, whereas scanning electron microscopy served for verification and evaluation purposes. Two types of films were studied, one less uniform and adherent and the other more compact and adherent. The results clearly show that pure mechanical removal in undisturbed single-phase flow does occur. However, film removal starts after an initiation period and is only localized. The differences in the thickness, microstructure, and topography of intact and residual films are discussed in detail for both film types. In addition, the possible mechanism of mechanical film removal from the fluid mechanics point of view has been proposed.