Development of an automated underwater abrasion rig to determine galvanic effects during the growth and localised breakdown of surface films in CO₂-containing solutions

This paper outlines the development of an automated underwater abrasion rig to assist in understanding the galvanic interaction induced by surface films when continuous localised mechanical film breakdown is encountered on the surface of carbon steel in CO₂-containing environments. The rig enables the measurement of galvanic current between a small X65 steel pin and a larger steel specimen, as well as the intrinsic corrosion rate of an additional, uncoupled larger specimen. The surface film developed on the pin is removed periodically using an automated reciprocating and rotating shaft with a sand paper grit pad attached to the base, while the surface film is allowed to establish itself undisrupted on the large specimen. The setup essentially simulates a tribo-corrosion process where local removal of material occurs within a carbon steel pipeline as a result of periodic sand particle impingement. Initial results focus on validating the reproducibility of the technique, as well as determining the galvanic effects associated with iron carbide and iron carbonate for two model sets of conditions to highlight the capabilities of the system.