Infrared microspectroscopic studies on the pitting of AA2024-T3 induced by acetone degreasing

Acetone degreasing of aluminum alloy AA2024-T3, as per the ASTM E1078-97 cleaning protocol, showed that copper-rich intermetallic particles acted as a photocatalyst in the presence of moisture to convert the acetone remaining on the surface to acetic acid. In this work, using synchrotron infrared microspectroscopy (SIRMS), we have investigated further the acetone-induced pitting of AA2024-T3 that was shown earlier using XPS. Using SIRMS prior to sodium chloride mist exposure shows the presence of carboxyl groups at sites where pitting is initiated, indicating that pitting is induced by acetone. The infrared linescan and mapping performed on acetone-degreased AA2024-T3 exposed to sodium chloride mist shows the presence of acetyl groups surrounding the pits. Based on this work, acetone is not recommended for degreasing aluminum-copper alloys. Copyright (C) 2001 John Wiley & Sons, Ltd.