Spray coat applications

Among the various applications which have not been treated in greater detail are the spray coat applications and the underlayment applications. The spray coat applications are based on combinations of cement and other fillers, together with a latex binder. These applications may be applied by banish, roller and trowel, as well as by spray. They are often promoted as a substitute for "rubbing" concrete. 

There are various experimental and numerical works that address spray characteristics in effervescent nozzles (e.g., [10, 37]). For instance, the variation of the droplet SMD versus the GLR at various injection pressures is shown in Fig. 24.24 [37]. The experimental data shown in Fig. 24.24 were obtained at the relatively low injection pressures that are of interest to gas turbine and spray coating applications. 

Loose asbestos fibers, or formulations containing asbestos fibers for spray coatings, have been widely used in the building industry for fire protection and heat or sound insulation. Such applications used mainly chrysotile or amosite but, because of health concerns, this practice has been discontinued. 

Zinc or aluminum metal spray Sprayed metal coatings are porous and should be sealed after application by applying a sealer coat (i.e. a thin coat such as an etch primer) or a thinned version of the final coating system. Oil-based systems should not be used. Metal spray coatings can have excellent durability without overcoating with paint and, particularly for aggressive conditions it is preferable to leave them with sealer only. 

The more automatic the method of coating application, the more economical and efficient it is, since automation lends itself more readily to more even coatings than do manual methods, e.g. large surface areas lend themselves more readily to spraying techniques, whereas open work structures are more suitable for dipping methods. The coating should also be applied to a specified minimum thickness which is adequate for the service conditions and life envisaged. 

A characteristic of the group (a) of resins is that they air-dry solely by solvent evaporation and remain permanently solvent soluble. This fact, combined with the need to use strong solvents, makes brush application very difficult, but sprayed coats can be applied at intervals of one hour. A full vinyl system such as (o) possesses excellent chemical and water resistance. Many members of group (o) have very poor adhesion to metal, and have therefore been exploited as strip lacquers for temporary protection. Excellent adhesion is, however, obtained by initial application of an etching primer the best known of such primers comprises polyvinyl butyral, zinc tetroxy-chromate and phosphoric acid. 

Thermoplastic resins, such as vinyl chlorides, vinyl acetates and polyamides are employed, particularly in the water industry, on buried pipes and fittings. To provide both internal and external coating, application may be by one of these principle techniques dipping in a plastisol, fluidised beds or electrostatic spray. 

Flow-coating and hand spray-gun application is sometimes employed where a relatively small number of large articles has to be phosphated. 

Water-base coatings for spray and roller coat application... 

A spray coating of aluminum on a steel is not likely to spall or flake, but the coating is usually not continuous and may leave some areas of the steel unprotected. Hot-dipped aluminized steel gives a continuous coating and has proved satisfactory in a number of applications. 

Water rinses are used in surface preparation operations such as acid pickling, alkaline cleaning, and nickel deposition to remove any process solution film left from the previous bath. A water rinse may also follow the neutralization step. Another common water use is in the ball milling process, which uses water as the vehicle for the enamel ingredients, as a cooling medium, and for cleaning the equipment. Coating application processes normally use wet spray booths to capture oversprayed enamel particles. Water wash spray booths use a water curtain into which the enamel particles are blown and captured. 

Water is used in this subcategory as solution makeup and for rinsing in the surface preparation process, as the vehicle for the coating in the application process (normally done by spray coating), and for cooling and cleanup in the ball milling operation. 

Electrostatics, effect on weighing, 26 243 Electrostatic self-assembly (ESA), of thin-films, 1 724-725 Electrostatic separators, 16 642 Electrostatic separation, 16 642-644 Electrostatic spray coating, 7 56-58, 74-75 Electrostatic stabilization, 10 119-121 of latex, 14 708-709 Electrosteric stabilization, 10 122 Electrostream (capillary drilling), 9 600 Electrostrictive coefficient tensor, 11 93 Electrostrictive devices, applications of, 11 103-104... 

Supercritical atomization in spray coating, 7 70 Supercritical carbon dioxide, 9 456,24 2, 15 applications of, 24 20 as a medium for chemical reactions, 12 808-809... 

Fan spray atomizers have been widely used in the spray coating industry (Fig. 2.5), in some small annular gas turbine combustors, and in other special applications that require a narrow elliptical spray pattern rather than the normal circular pattern. In particular, fan spray atomizers are ideal for small annular combustors because they can produce a good lateral spread of fuel, allowing to minimize the number of injection ports. 

Similar to screen printing, the spray coating method [95] is widely used for catalyst fabrication, especially in labs. The major difference between the two is that the viscosity of the ink for spray coating is much lower than that for screen printing. The application apparatus can be a manual spray gun or an auto-spraying system with programmed X-Y axes, movable robotic arm, an ink reservoir and supply loop, ink atomization, and a spray nozzle with adjustable flux and pressure. The catalyst ink can be coated on the gas diffusion layer or cast directly on the membrane. To prevent distortion and swelling of the membrane, either it is converted into Na+ form or a vacuum table is used to fix the membrane. The catalyst layer is dried in situ or put into an oven to remove the solvent. 

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