Ozone treatments have been shown to reduce the outgassing rates in ultrahigh vacuum for several metals. We have further studied surface cleaning employing supercritical fluid CO2 which has high solubility for hydrocarbons. The sample measured was a half section of an anodic oxidized Swagelok fitting (A2024) 10.8 mm diameter and 8.5 mm in length saw sectioned along the axis. The cut surface was used as the reference surface. The treated and untreated surfaces were analyzed by x-ray photoelectron spectroscopy, evaluating the surface carbon density obtained from the ratio of the convoluted area of Al((2)p), O((1)s), and C((1)s) peaks. Carbon density of the untreated surface is 87%. Following the treatment with supercritical fluid CO2 at 50 degrees C and 80 atm for 2 h, the carbon was reduced to 65%. Treating at 2 h at 70 degrees C and 94 atm showed the same 65% carbon. Adding water and increasing the supercritical fluid CO2 pressure to 100 atm showed carbon at 57%. However, adding some salt (NaCl) to the mixture produced a dramatic carbon reduction to as low as 13%. No pressure dependence was observed.