Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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VOC than "x" lb/gal, less water. In the case of a 3.5 lb/gal limit, the regulation would specifically state that the coating may not contain more than 3.5 lb/gal, less water. The following calculations will demonstrate this concept. Example 1: Single-Component Solvent-Borne Coating Plus Water A state regulation limits you to a coating for which the VOC is less than 3.5 lb/gal, less water. You purchase 1 gal of solvent-borne coating, which contains no water, but has a VOC content of 5.0 lb/gal. To bring down the VOC content you decide to add 1 gal of water. What is the VOC content, less water, of the mixed coating? Would it now meet the regulatory requirement? Regardless of how much water is added, the VOC content remains 5.0lb/gal, less water, and continues to be in violation of the regulation. Example 2: Two-Component Solvent-Borne Coating Plus Water What is the VOC content of the following two-component epoxy? Is it in com- pliance with a regulatory limit of 2.8 lb/gal, less water? The coating consists of three parts of Component A at 3.1 lb/gal, one part of Component B at 1.8 lb/gal, and 7 parts of water. (See Table VI.) Neither Component A nor B contains water. Notice that when you calculate the VOC of the coating mixture for compliance purposes, you must ignore the water altogether. Hence, in Column 2 the total is 4 and not 7. VOC = 11.1/4 = 2.75 lb/gal, less water The mixture is in compliance with the regulation. Example 3: Two-Component Solvent-Borne Coating Plus Water You are provided with the following information concerning a waterborne coat- ing. What is the VOC content, less water? The volume of water is 52%, the volume solids is 42%, and the density of the VOC only is approximately 7.36 lb/gal. The % volume of VOC in the coating = 100 - 42 - 52 = 6%. For 1 gal of coat- 315

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