The role of manganese in the corrosion behavior of commercial Al-Mn alloys has been examined by means of corrosion tests and metallographic techniques. Alloys containing 0.4-1.2% Mn, 0.4-0.8% Fe, 0.15% Si and some with small amounts of magnesium have been fabricated and evaluated. Results have shown that corrosion resistance increases with an increase in the Mn/Fe ratio in the alloy, but remains unaffected by the magnesium addition. The beneficial role of manganese is interpreted as reducing the difference in potential between the matrix and the intermetallics because of the supersaturation of manganese in the aluminum matrix and the manganese enrichment of the intermetallics. This reduction in the potential difference between the matrix and the intermetallics decreases the extent of overall corrosion.

The anodic oxidation of nickel in 1N H2SO4 solution has been studied employing potentiostatic and galvanostatic techniques. It has been found that although a large amount of charge is consumed during anodic oxidation, only about 5% of this charge is involved in film growth. The thickness of the passive film on nickel in 1N H2SO4 is between 6–16Å for anodic oxidation times of 15–60 min. The experimental results have been used to develop a kinetic equation describing the film growth on nickel. It is shown that the logarithm of the film growth current density is inversely proportional to the charge stored in the film. The resistivity of the film suggests that the film is pure and almost stoichiometric normalNiO . It is suggested that the Flade potential of nickel in 1N H2SO4 corresponds to that potential, more noble than the passivation potential, at which the surface of the nickel is covered with a pore‐free film of normalNiO and passivation is complete.

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The effect of grain size and cold work on the anodic polarization behavior of polycrystalline nickel in acidic chloride solution has been investigated using potentiostatic techniques and in situ microsc~opic observations. A variation in grain size from 0.025 to 0.330 mm and cold working to 40% does not affect the critical breakdown potential. It is concluded that the critical breakdown potential is not an adequate measure of the electrochemical conditions required for pitting corrosion of nickel. * Electrochemical Society Student Member.