Thin coat

Apphcations of microhardness testing greatly extend the conventional indentation hardness test to glass and ceramics, metaHographic constituents, and to thin coatings or other surface treatments not otherwise testable. 

At high neutralization levels with alkaH metal ions, many ionomers spontaneously form coUoidal suspensions in water when stirred vigorously at 100—150°C under pressure. Depending on soHds content and acid level, the dispersions range in viscosity from water-like to paste-like. These provide convenient methods for applying thin coatings of ionomers to paper and other substrates. 

Rubber. A thin coating of mica acts as a mold-release compound in the priming of mbber goods such as tires. It prevents the migration of sulfur from the tire to the air bag when the tire is being vulcani2ed (see Tire cords). Mica is also dusted on mbber inner tubes to prevent sticking. 

Seeds. The seeds are produced in pods containing two or three seeds. The kernels are almost spherical to roughly cylindrical (0.4—1.1 g each) and consist of a thin coat (testa) containing two cotyledons and the embryo. Cotyledons contain protein bodies, Hpid bodies, and starch granules. 

Tin is used in various industrial appHcations as cast and wrought forms obtained by rolling, drawing, extmsion, atomizing, and casting tinplate, ie, low carbon steel sheet or strip roUed to 0.15—0.25 mm thick and thinly coated with pure tin tin coatings and tin alloy coatings appHed to fabricated articles (as opposed to sheet or strip) of steel, cast iron, copper, copper-base alloys, and aluminum tin alloys and tin compounds. 

In many of the thin coatings on cemented carbide, either single or multiple coatings of single phase materials, such as TiC, are used. It would appear that extending the use of soHd solutions of multicarbides of W, Ti, and Ta or Nb for coatings may further enhance the performance of the coated carbides. It would not be difficult to accomplish this either by CVD or PVD techniques. 

In the computer industry, new read/write optical discs, capable of storing over 250 megabytes, utilize a thin coating consisting of a germanium, teUurium, and antimony compound (see Imaging TECHNOLOGY). 

Electrostatic spraying is used in shops to coat conductive objects. It is very useful for odd-shaped objects such as wire fence, cables, and piping. An electrostatic potential of 60,000 volts on the object attracts oppositely-charged paint particles the spray can wrap around and coat the side of the object opposite to the spray gun. This technique produces very uniform finishes and has the least paint loss of the three methods. However, it is slow, requires expensive equipment, produces only thin coats, and is sensitive to wind currents. 

Coa.ting S. CR has been used to coat a variety of substrates, from cloth for rainwear to concrete decks for protection against salt water. A sol-type latex is preferred to ensure good adhesion to concrete decks. A crystalline polymer latex is preferred where added durabUity is needed. The compound includes a nonionic surfactant to improve its chemical stabUity. A number of thin coatings are appUed to the surface to allow better coverage and facUitate drying. A similar formulation could be used to coat the interior of tanks, but an accelerator is needed to improve toughness. 

Sodium borohydride or dimethylarnine borane have found limited use as reduciag agents because of expense. In addition, bath stabiHty, plating rate, and deposit properties are inferior to those of formaldehyde-reduced baths. The deposit is a copper—boron alloy. Copper—hypophosphite baths have been iavestigated, but these are poorly autocatalytic, and deposit only very thin coatings. 

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