Studies of latex paint films exposed to aqueous SO2: pH effects

✍ Scribed by J. R. Xu; C. M. Balik

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 561 KB
• Volume: 39
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1990.070390911

✦ Synopsis

Latex paint films containing the acid-soluble extender calcium carbonate have been exposed to aqueous SO2 and other acidic solutions to evaluate the effects of acidic deposition at different pH values on the coatings. CaC03 is completely removed from these films upon immersion in acidic solutions. The leaching process was monitored with weight loss and infrared measurements. The removal rate was found to be strongly dependent on pH, decreasing with increasing pH. Removal of CaCO, occurs even for distilled water which has been allowed to equilibrate with atmospheric C02 (pH 5.6). The removal rate seems to depend only on [H+]; the identity of the acidic anion is apparently insignificant. An empirical relation between the rate of removal and pH was formulated from the weight loss data. The analyses of the results from both weight loss and infrared methods suggested that the mechanism of removal at pH 2.0 is diffusion controlled, whereas a chemical reaction involving H+ becomes more important at higher pH values.