Metal Finishing Guide Book


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ance 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 coating. 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 coating, the volume of VOC is 0.06 gal and the volume of solids is 0.52 gal. If you remove the water from the coating, the total volume of the VOC plus solids is 0.58 gal. Suppose you wanted to fill a 1-gal can with only the VOC plus solid, then the total volume of VOC in the 1-gal can would be: 0.06/0.58 = 0.103 gal If the approximate density of the VOC is 7.36 lb/gal, then the VOC content of the coating, less water, is given as 0.103 gal x 7.36 = 0.76 lb/gal CONVERTING FROM ENGLISH TO METRIC UNITS Many of the regulations are not written in lb/gal, but rather in grams per liter (g/L). The conversion is as follows: 1 lb/gal = 119.8 g/L Table VII shows the VOC limits most commonly found in regulations, but be aware that the conversions are not exact. With the exception of 1 lb/gal, the values in the table have been rounded off. 817

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