Organic Coatings and Paints

Epoxy resin paints, inferior to chlorinated rubber for resistance to strong acids, are excellent for dilute acids and strong alkalis. They produce a harder, more abrasion-resistant coating than does chlorinated rubber and are much better for resistance to fats, oils and many organic solvents. Table 3.50 gives data on the chemical resistance of epoxy resin coatings to different materials. 

Stoved phenolics have outstanding acid resistance (up to 200°C in dry conditions and up to 100 C in wet conditions), except to strong oxidizing acids. They are unsuitable for use with alkaline solutions above pH 10, wet chlorine or hypochlorite solutions. Phenolics/silicon formulations can be used for steam up to 180°C without a significant effect on heat transfer rates. 

Polyester/glass-flake linings can be applied onsite because they cure at ambient temperature. Their corrosion resistance depends on the type of polyester resin used. 

PVC plastisol coatings are tough, with an abrasion resistance similar to rubber. They are resistant to acids and alkalis but usually are not suitable for solvents because of extraction of the plasticizers in the coating. 

Most plastics are now available as powders and can be applied as coatings by fluidized bed or spraying techniques. Nylon 11 and polyethylene have proved most useful for chemical plant applications. 

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The most important source of CH3I formation seems to be the reaction of I2 (and possibly of HI) present in the gas phase with organic materials present on surfaces, primarily organic coatings and paints. In this reaction mechanism, I2 from the atmosphere is deposited onto the surface where a part of it is converted to organoiodide and is subsequently released to the atmosphere again according to... 

Organic coatings and paints are also able to provide EMF control protection. Surface conditions are converted to more stable states by coating with organic compounds. These coatings delay the generation of electromotive force, causing the corrosion of the substrate. 

Organic pigments are used to color a variety of media. It is useful to distinguish between three primary fields of application the coatings and paints industry, the printing inks industry, and the plastics and fibers industry. Besides, organic pigments are used for special purposes, for instance in office materials and in the mass coloration of paper. 

P.V.23, also referred to as Carbazole Violet, is a universally useful product. Its color, a bluish violet shade, is not accessible with other Pigments. P.V.23 is used in almost all media which are typically colored with pigments. The list of suitable systems ranges from coatings and paints to plastics, printing inks, and other special-purpose media. P.V.23 is entirely fast to many organic solvents. At standardized conditions (Sec. 1.6.2.1), it is fast to alcohols, esters, and aliphatic hydrocarbons as well as to plasticizers such as dibutyl and dioctyl phthalate. Other solvents, such as ketones, are colored slightly (step 4). 

Thin films of organic compounds are often applied from solvents. These films include adhesives, coatings for magnetic tapes, inks, paints, and varnishes. Over 11% of all products have some kind of coating. Worldwide sales of coating-based products are over 5 trillion dollars.285 A number of reviews of surface coatings and paints are available.286 Several other reviews cover ways to minimize the use of solvents in these.287 Much of the discussion that follows is taken from these latter reviews. 

Floating platforms are generally protected by CP (sacrificial anodes or impressed current) combined with a high-quality paint system. Pipelines with an organic coating and an external concrete coating are also protected by sacrificial anodes. 

Paints and varnishes, although chemically similar to polymeric coatings, differ by the way they are applied, which, most often, involves the use of a carrier water or an organic solvent. However, there are exceptions to this rule the application of certain oven-dried paints and varnishes used in the automobile industry and elsewhere does not require a carrier. The separation between polymeric coatings and paints is therefore not sharp. Several layers of paint are usually applied to metal surfaces that... 

Perera, D.Y., Stress phenomena in organic coatings, in Paint and Coatings Testing Manual 14th ed. Of Gardner-Sward Handbook, Koleske, J.V, Ed., ASTM, Philadelphia, PA, 1995. 

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