Published: Jan 2012
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A PAINT, EVEN ONE AS SEEMINGLY SIMPLE AS A red-lead alkyd, is actually a very complex system wherein a variety of components such as polymers that may or may not contain reactive functionality, pigments, plasticizers, additives, and solvents must interact in such a way that the dried film offers expected protection. In addition, quite often, the film is expected to provide an aesthetic appeal. Because of this complexity, it is not surprising that the complete chemical analysis of a coating can be a complicated and time-consuming task. Indeed, a complete analysis of all the components may require the use of several analytical techniques, many of which are discussed in this manual. The intent of this chapter is somewhat more limited, as it pertains only to the analysis of coatings for metallic constituents and more specifically, elements. Such compounds are widely used in the coating industry. Many pigments and extenders are inorganic compounds that may contain metals, and many driers, catalysts, and ultraviolet (UV) light absorbers are metal-containing compounds as, for example, cobalt naphthenate and dibutyltindilaurate. It should be pointed out that in theory inductively coupled plasma spectroscopy can be used to analyze all elements except argon. However, in actual practice, it applies to approximately 70 elements, many of which are not typically considered metallic by most paint chemists. Classical wet chemical techniques are valuable in determining several of the above-mentioned paint-component compounds. However, a generally simpler, more efficient, and, in some cases, more sensitive way to achieve this involves the use of the related techniques of atomic absorption (AA), atomic emission (AE), and inductively coupled plasma (ICP) spectroscopy. It is the purpose of this chapter to briefly describe the underlying principles of these techniques and to discuss their usefulness within the coating industry.
Weldon, Dwight G.
President, Weldon Laboratories, Inc., Imperial, PA