Pitting corrosion of aluminum

Inorganic acids, bases, and salts with pH values <4 and >9 are not compatible with aluminum. Pitting corrosion of aluminum can occur when it comes in contact with salt water and copper halide salts. 

H. Kaesche. Pitting Corrosion of Aluminum and Intergranular Corrosion of A1 Alloys, in Localized Corrosion. 1971. Williamsburg, VA NACE, Houston, TX. 

E. V. Gheem, R. Pintelon, A. Hubin, J. Schoukens, P. Verboven, O. Blajiev, and J. Vereecken, "Electrochemical Impedance Spectroscopy in the Presence of Non-Linear Distortions and Non-Stationary Behavior II. Application to Crystallographic Pitting Corrosion of Aluminum," Electrochimica Acta, 51 (2006) 1443-1452. 

As with other active-passive-type metals and alloys, the pitting corrosion of aluminum and its alloys results from the local penetration of a passive oxide film in the presence of environments containing specific anions, particularly chloride ions. The oxide film is y-Al203 with a partially crystalline to amorphous structure (Ref 13, 59). The film forms rapidly on exposure to air and, therefore, is always present on initial contact with an aqueous environment. Continued contact with water causes the film to become partially hydrated with an increase in thickness, and it may become partially colloidal in character. It is uncertain as to whether the initial air-formed film essentially remains and the hydrated part of the film is a consequence of precipitated hydroxide or that the initial film is also altered. Since the oxide film has a high ohmic resistance, the rate of reduction of dissolved oxygen or hydrogen ions on the passive film is very small (Ref 60). 

L. Tomcsanyi, K. Varga, I. Bartik, G. Horanyi, and E. Maleczki, Electrochemical Study of the Pitting Corrosion of Aluminum and Its Alloys II, Study of the Interaction of Chloride Ions with a Passive Film on Aluminum and Initiation of Corrosion, Electrochim. Acta, Vol 34, 1989, p 855-859... 

Plots of maximum depth of pitting corrosion on 1000 and 3003 alloy sheet and the percent loss in strength resulting from exposure to seacoast atmosphere at Point Judith, Rhode Island. Both curves show the self-stopping nature of pitting corrosion of aluminum but at different rates of change. The rationale behind the difference is discussed in Section 19.7. (Courtesy of Alcoa Technical Center, Marsha Egbert.)... 

Z. Szklarska-Smialowska (1999), Pitting corrosion of aluminum , Corros. Set, 41 1743-67. 

Quantitative data on the pitting corrosion of aluminum and aluminum alloys in seawater can be found in Chapter 8. 

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