Corrosion behaviour of oxide film formed on carbon steel in high temperature alkaline water in the presence of zinc and magnesium ions

Magnetite films on carbon steel are known to reduce corrosion in high temperature aqueous medium. The magnetite films were modified in-situ by introducing Zn and Mg in autoclave by hydrothermal process at 250 degrees C. The film developed in the presence of Zn were thinner with particle size 150 nm after 240 h exposure compared to that developed in the presence of Mg with particle size 223 nm. The depth distribution of Zn and Mg monitored by Rutherford backscattering spectrometry showed that Mg was present more at the top surface, whereas Zn were almost uniform across the depth of the film. Contact angle measurements and electrochemical studies of coated specimens showed an increased corrosion resistance in presence of Zn and Mg in comparison to known passive magnetite layer formed in their absence. It was shown that Zn is a better candidate for corrosion resistance of carbon steel in high temperature aqueous medium.

Automated summary

The magnetite films on carbon steel can be modified in-situ with the introduction of Zn and Mg by hydrothermal process. The film developed in the presence of Zn showed a smaller particle size of 150 nm after 240 hours exposure compared to that developed in the presence of Mg with a particle size of 223 nm. The depth distribution of Zn and Mg showed that Mg was mainly present on the top surface, while Zn was distributed uniformly across the film depth. Contact angle measurements and electrochemical studies demonstrated that Zn and Mg improved the corrosion resistance of the coated specimens when compared to the passive magnetite layer formed without their presence. The results suggest that Zn is a better candidate for corrosion resistance of carbon steel in high temperature aqueous medium.