Understanding the anticorrosion mechanism of phosphonium based ionic liquid for steel in brine water containing H2S and CO2

Abstract

Carbon steel is being significantly considered for applications in the petroleum field. However, the corrosion of steel structures in the petroleum sector due to H2S, CO2 and brine solution is a limiting factor for the development of such metal. Here we use phosphonium based ionic liquid (i.e. Tributylmethylphosphonium Bis(trifluoromethanesulfonyl)imide, abbrev. PBIL) to control the corrosion of steel structures in brine water containing H2S and CO2 at pH of 2. The carbon steel suffers from high corrosion in the brine water containing H2S. Furthermore, H2S/CO2 system provides lower corrosive effects than a pure H2S system. The corrosive action of H2S/CO2 system becomes stronger at high temperatures. The incorporation of PBIL ionic liquid in brine water containing H2S and CO2 reduces the corrosion effects on steel structures, resulting in a much higher lifetime. PBIL ionic liquid adsorbs on steel structure surface to form a protective film, which is evidenced by Freundlich isotherm and confirmed by SEM and EDX tests.