Pigments and Paints

Metals may be introduced into paints as the principal constituents in pigments, in drying oils, in pesticides or antifouling compounds and as markers in security paints. The need to monitor metal levels arises from the effects trace metals may have upon the colour or quality of the paint, its toxicity or in forensic applications. Many countries have legislation specifying the maximum permissible levels for toxic elements in toys. The British Toy (Safety) Regulations 1974 [144] sets dry weight limits in paint or varnishes on toys for soluble barium of 500 ppm, soluble antimony and 

Oils and thinners may be diluted with white spirit or MIBK, usually by at least a factor of 10 to promote efficient nebulisation. Metal napthenates can be used as standards [67]. Paints as well as the oils above may be diluted with methyl isobutyl ketone (MIBK) for direct injection into a graphite furnace. 

Many paints require vigorous pre-treatment before the matrix can be destroyed. Even after considerable oxidation it may be necessary to filter off titanium dioxide. Some paints are, however, more amenable to acid dissolution. Eider [147] reported that it was possible to determine barium, cadmium, calcium, cobalt, lead, magnesium, manganese, mercury, tin, zinc and zirconium in vinyl additives and paint (1 g) by dissolution in hot concentrated nitric acid (10 ml). The mixture was filtered and made up to 100 ml. Liquid samples were again dissolved in MIBK (lg in 100 ml). Air/ acetylene and nitrous oxide/acetylene flames were used to complete the analysis as appropriate. Porter [148] reported losses of lead during the dry ashing of alkyd and latex paints and therefore recommended dissolution in either nitric/perchloric acids or nitric acid alone. 

Price s review [145] gives an excellent account of the mode of occurrence of metals in major constituents in paints and some recommended operating conditions for flame atomic absorption. It may be increasingly necessary to add to the list more exotic metals because of their growing use as markers in security paints. 

Very often a rapid answer is required as to whether a paint does or does not contain high levels of lead. The above methods lack rapidity and there 

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Coatings, Paints, and Pigments. Various slightly soluble molybdates, such as those of zinc, calcium, and strontium, provide long-term corrosion control as undercoatings on ferrous metals (90—92). The mechanism of action presumably involves the slow release of molybdate ion, which forms an insoluble ferric molybdate protective layer. This layer is insoluble in neutral or basic solution. A primary impetus for the use of molybdenum, generally in place of chromium, is the lower toxicity of the molybdenum compound. 

Paint and pigments Ceramics, talc, and clay Paper and plastic fillers Expression belt 33 57... 

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

Some types of paints and pigments that are used as facial make-up or hair coloring contain lead. Cosmetics that contain lead include surma and kohl, which are popular in certain Asian countries. Read the labels on hair coloring products, and keep hair dyes that contain lead acetate away from children. Do not allow children to touch hair that has been colored with lead-containing dyes or any surfaces that have come into contact with these dyes because lead compounds can rub off onto their hands and be transferred to their mouths. 

Mercury(II) oxide is found natively in the mineral montroydite. The oxide is used primarily to prepare other mercury salts. The red form of the oxide is used as a depolarizer in a certain type of dry batteries. Other applications are paints and pigments as a reagent in several wet analyses and to catalyze in organic reactions. The oxide also is used in ointments as a topical antiseptic. 

Mercury is mined predominantly as HgS in cinnabar ore and is then converted commercially to a variety of chemical forms. Key industrial and commercial applications of mercury are found in the electrolytic production of chlorine and caustic soda the manufacture of electrical equipment, thermometers, and other instruments paint and pigment production dental amalgam and gold refining. Use in pharmaceuticals and in biocides has declined substantially in recent years, but occasional use in antiseptics and folk medicines is still encountered. Environmental exposure to mercury from the burning of fossil fuels—or the bioaccumulation of methylmercury in fish—... 

Rare earths are used in the paints and pigments industry (i) as coating materials for pigments to enhance their durability and performance characteristics, (ii) in the manufacture of ceramic pigments and (iii) in the manufacture of driers for organic coatings. 

Lead is very important for development of the various sectors of India s economy. For example, it is necessary for advanced development of the electrical industry, the paints and pigments industry, and other areas. The chief need of the industry is for the location and development of additional ore bodies. 

Calculated from data in the U.S. Geological Survey Minerals Yearbook [44]. Includes other paint and pigment uses as well as titanium dioxide. 

The total reflectance of an optically thick layer of dyed particles of AgBr can be measured with a spectrophotometer equipped with an integrating sphere. One then interprets the reflectance spectrum with the aid of Kubelka-Munk functions (20), as is commonly done with paints and pigments. 

Maternal exposure to paints and pigments, metal dusts and sawdust was reported significantly more frequently by the parents of children with acute lymphocytic leukemia in a farther case control study [5]. 

One of zinc oxide s most important uses historically is in paints and pigments. Common names by which it is now known, such as Chinese white and zinc white, are terms long used by artists for the compound. White paints and pigments made with zinc oxide retain their luster and purity longer than most other types of white paints, partly because zinc oxide does not react readily with hydrogen sulfide in air that causes most white paints to darken. 

Solvents and pigments need not always be present in a coating formulation. Solvent-free paints and pigment-free varnishes are also available. 

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