Abstract
The formation, breakdown and composition of surface films on copper in air-saturated solutions at 25°c has been studied by potentiokinetic polarisation. In 0·01 M NaHCO3, the protective oxide layer breaks down at a critical potential togive pitting corrosion. Increasing the concentration of hydrogen carbonate ions decreases the protectiveness of the oxide film towards general corrosion, but makes the filmmore resistant to breakdown. In 0·01 M NaCl, the oxide film formed is initiallyfairly protective and exhibits a breakdown potential on rapid polarisation. As the chloride concentration is increased, the oxide film becomes less protective and the breakdown potential becomes displaced to more negative potentials and is more poorly defined.
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