EFFECTS OF ACIDIC DEPOSITION ON PAINT - A CHAMBER STUDY

Exterior acrylic latex and alkyd architectural coatings were exposed t o different conditions in a chamber exposure system involving simulate d sunlight, dew, and photochemical smog containing sulfur dioxide (SO2 ). A simulated sunlight exposure of the coating films in the presence of clean air also was incorporated into the experimental design. Chang es in surface features after 1,370 hours of exposure were characterize d by scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX). Gaseous species that deposited on the films were de termined by ion chromatography (IC) of the dew collections. Color-chan ge measurements of the exposed films were recorded as ''Delta E'' valu es. Latex and alkyd films that were formulated with calcium carbonate (CaCO3) as an extender pigment were found to undergo the most change i n surface features, composition, and color.