Corrosion Classification coupon: The Corrosion Classification Coupon (CCC) measures the amount of corrosion that forms on copper and silver surfaces. This provides data allowing an industry standard classification of the amount of corrosion present, as well as identifying contaminant classes. Because many contaminants are corrosive in nature (e.g., hydrogen sulfide and sulfur dioxide), reactivity monitors have long been used to gauge the quality of ambient air and to indicate the effectiveness of pollution control strategies. Purafils CCC is a passive reactivity monitoring technique involving the use of copper and silver.