Abstract
Pitting corrosion behaviour of modified 9Cr- 1Mo ferritic steel containing 100 ppm of boron was studied in deaerated 0.1, 0.2 and 0.5 M sodium hydroxide solutions containing 0.1, 0.2 and 0.5 M sodium chloride. The chemical compositions of the passive film developed at applied potentials were studied using XPS. Epit values decreased with increase in chloride concentrations for the given concentration of alkali. The effect (of Cl - ) was less pronounced in higher alkali concentrations. Pit diameters were observed to be significantly higher in 0.1 M sodium hydroxide containing 0.1 M sodium chloride; with increase in alkali concentration pit diameters were found to be restricted to lower values even at higher chloride concen- trations. Energy dispersive spectroscopic (EDS) studies showed that pits had nucleated at Al2O3 inclusions/matrix interface. XPS analysis revealed the presence of Fe3O4, Fe(OH)3 at lower potentials (150 and 209 mV(SCE)) whereas Fe2O3, Fe(OH)3 and FeO2 2- at higher potentials (400 and 650 mV(SCE)).
Published Version
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