Fourier-transform infrared/attenuated total reflectance (FTIR–ATR) has been used to investigate the effects of acidic deposition on latex paint films with and without a calcium carbonate extender additive. Paint films approximately 5 mils thick were exposed to aqueous SO2(pH 2.0) for various times by simple immersion. Rapid and complete removal of CaCO3 from the paint film was found to occur, and the kinetics of the removal process were monitored using both weight loss and FTIR–ATR measurements. Both methods revealed Fickian diffusion, with an apparent diffusion coefficient D = 1.84 × 10−9 cm2/s. Good agreement was obtained between D measured via FTIR–ATR and from the weight lost data. The mechanism of removal of CaCO3 from the latex paint films appears to be controlled by the rate at which water and other components of the aqueous SO2 solution can diffuse into the film.