Effect of formic acid (HCOOH) on the corrosion protectiveness of magnetite (Fe3O4) at elevated temperature

The corrosion behavior of carbon steel in an aqueous solution containing dissolved CO2, H2S, and HCOOH at high temperature was investigated by conducting a series of systematic experiments. The influence of each (possible) corrosive species (CO2, H2S, and HCOOH) on corrosion mechanisms were explored through detailed analysis of corrosion rates and corrosion product layers. The results showed that the formation and integrity of the Fe3O4 layer was compromised in the presence of HCOOH, probably due to the formation of Fe(COOH)+ which impedes the formation of Fe3O4 at the initial stage of the corrosion process.