The effect of the metal cations, Na + , K + , Ca 2+ , Mg 2+ , Zn 2+ , and Ni 2+ , on the oxide film structure and morphology changes during long term immersion corrosion tests of aluminum alloy (A3003) in model tap waters was investigated by X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The effect of the metal cations on the corrosion behavior was also investigated with mass change and electrochemical tests. The hardness of the metal cations, X, based on the Hard and Soft Acids and Bases (HSAB) concept was applied to explain the effect of metal cations on the passive oxide film structure and corrosion resistance. The mass change rate and corrosion current density decreased with increasing metal cation hardness. The XPS results showed that hard metal cations like Zn 2+ and Ni 2+ were incorporated in the oxide films, while the four soft metal cations were not incorporated in the oxide films.The results are in good agreement with those which could be expected from the HSAB hardness of the metal cations.

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The effects of metal cations on the galvanic corrosion behavior of the A5052 aluminum alloy in low chloride ion containing solutions (tap water) were examined by electrochemical noise impedance. The electrochemical noise impedance and conductance were calculated by the power spectral density (PSD) of the galvanic current and potential.The oscillations in the galvanic current correlate well with the oscillations in the potential.The total charge (summation of galvanic current) during galvanic corrosion tests was suppressed by the addition of Ca 2+ , while it was increased with Mg 2+ addition. Only a small effect on mean impedance and conductance was observed in solutions with Cu 2+ and Mg 2+ , while addition of Ca 2+ strongly influences both the mean impedance and conductance.These results may be explained by the passive film structure changes due to the metal cations. The results obtained in this study indicate that metal cations play a very important role in the corrosion behavior of A5052 aluminum alloys in tap water.

Effect of a kind of metal cation on corrosion mechanism of A3003 aluminum alloy in tap water was investigated by electrochemical techniques and immersion corrosion tests. Corrosion rate of the aluminum alloy decreased with increase in a hardness of cation, except for Mg 2+ . XPS analyses showed metal cations, classi ed as a hard acid in tap water were incorporated in hydroxides on the aluminum alloy. The results suggest that the incorporated cations have corrosion inhibitory effect (e.g., Ca 2+ and Zn 2+ ) or corrosion promotive effect (e.g., Mg 2+ ). These different effects can be explained by difference in molar volume between hard metal cation s hydroxide and aluminum hydroxide.

The effect of metal cations, Na + , K + , Ca 2+ , Mg 2+ , Zn 2+ , and Ni 2+ , on oxide film structure and morphology changes during immersion corrosion tests of 3003 aluminum alloy in model tap waters was investigated by surface analysis techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The hardness of metal cations based on the hard and soft acids and bases (HSAB) concept was applied to explain the effect on the passive oxide film structure. Numerous nano-sized pits were observed after 86.4 ks immersion in model tap water, and nano-sized corrosion products were also observed especially in specimens immersed in K + containing solutions. The AES and XPS results showed that hard metal cations like Zn 2+ and Ni 2+ were included in the oxide films, while soft metal cations were not included in the oxide films. The results are in good agreement with those which could be expected from the HSAB hardness of the metal cations.