The role of ferrite-cementite interface in formation of hierarchical film on carbon steel in CO2-saturated brine

Abstract

Carbon steels with ferrite-pearlite structures are commonly used materials in many industrial operations, and their protection against corrosion often relies on preventative inhibition measures. Film-forming corrosion inhibitors are known to provide protection to carbon steels in oil and gas productions lines for decades. However, the mechanisms of how these protect against corrosion are not known. Corrosion inhibitor films with hierarchical structures can be protective to the steel surface due to their large surface area and interconnected hierarchical porosity. The compounds that contribute to the formation of hierarchical morphology can be components of corrosion inhibitor formulations.This study demonstrates solution deposition of a hierarchically structured film derived from sodium thiosulphate. The film forms on an AISI 1030 carbon steel (UNS G10300) substrate in CO2-saturated sodium chloride containing solution under ambient conditions. We identified that the hierarchical film derived from sodium thiosulphate occurs originally at the interface of ferrite-cementite phase in pearlite and elucidate the role of oxygen in the formation of the hierarchical structures. These findings are expected to facilitate developments of novel corrosion inhibition strategies, through a controlled growth of surface films at metallic substrates for specific applications, including corrosion protection in oil and gas industry, catalysis and energy-storage applications.