Abstract
The oxide films formed on pure iron and mild steel in air at ambient temperatures show marked differences in their behaviour in 0·5 M H2SO4.
On pure iron the air-formed oxide film persists for a considerable time in 0·5 M H2SO4, retarding the anodic reaction and giving a more positive corrosion potential than for anaerobically treated samples. It also reduces the effectiveness of corrosion inhibition by quaternary ammonium ions.
With mild steel, the air-formed oxide film has the opposite effects. The anodic reaction in 0·5 M H2SO4 is stimulated, giving a more negative corrosion potential, and corrosion inhibition by quaternary ammonium bromides is enhanced. From this, and other evidence, it appears that the oxide layer on mild steel is rapidly removed in 0·5 M H2SO4, leaving the anodic sites in a more active state than those on anaerobically treated samples.
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