Coating process

The type and amounts of clay and regulating salts (potassium, sodium, magnesium salts and borax) influence the consistency of slips and depend upon the chosen coating process. Their addition should bring about a easily flowing, slightly thixotropic slip, which does not readily settle on standing. 

For some time finished enamels have been utilized for wet application, which have to be premilled dry with mill admixtures. The necessary quantities then only have to be stirred with water to a utilizable suspension. 

In dry coating processes the frit is ground dry with or without additives to the required fineness. For powder coating no further additives are necessary. Powders for electrostatic coating have to be hydrophobized to adjust the specific resistivity of the powder surface to lO to 10 Clem. This is achieved by adding charging agents to the mill. Special silicones are especially suitable therefor. 

Dry premilled enamel frits and mill admi, tures can be introduced in water into the slip 

Powders for electrostatic coating are brought to a. specific re.si.stivity of at lea.st 10 Q-cm by coating with silicone oils 

In the previous chapter, the processing of refractory carbides and nitrides in the form of powders, bulk/monolithic shapes, frbers, and whiskers was reviewed. These materials have one other major form, i.e., coatings, and the review of coating processes is the objective of this cluster. 

Coatings of refractory carbides and nitrides have great industrial importance with a wide range of applications in semiconductors and other electronic components, in cutting tools, gas-turbine vanes and blades, precision bearings, punch sets, extruders, prostheses, and many other products. 

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To prevent rejects, retouching and to reduce cost of conservatively more than enough applied powder in powder coating processes a handy measurement system allowing to determine the... 

Two basic methods are used for the appHcation of protective coatings to metal containers, ie, roUer coating and spraying. RoUer coating is used if physical contact is possible, eg, coating of metal in sheet and coil form. Spraying techniques are used if physical contact is not possible, eg, to coat the inside surface of two-piece drawn and ironed can bodies (see Coating processes). 

The coating process, outlined in Figure 6, starts either with the specification of appropriate titanium substrate material for new anodes, or with... 

Each type of metallic coating process has some sort of hazard, whether it is thermal energy, the reactivity of molten salt or metal baths, particulates in the air from spray processes, poisonous gases from pack cementation and diffusion, or electrical hazards associated with arc spray or ion implantation. 

The appHcation of this type of conversion coating can be by spray or immersion and is easily tailored to the needs of the user (see Coating processes). The number of stages may vary from two, ie, clean and phosphate then rinse, to as many as five, ie, clean, rinse, phosphate, rinse, and post-treat. The performance requirements dictate the number of operation stages as well as the need for a post-treatment. 

The bath components for a nitrite—nitrate accelerated bath basic to this conversion coating process are (/) 2inc metal or 2inc oxide dissolved in acid (2) phosphate ions added as phosphoric acid (J) addition of an oxidant such as sodium nitrite and (4) addition of nitric acid. Other oxidants such as peroxide, chlorate, chlorate in combination with nitrate, or an organic nitro compound may also be used. 

When selecting a particular paster adhesive, coating material, and coating process for sohd fiber packaging, the fact that sohd fiberboard lacks the open-flute stmcture (to facihtate exit of moisture from internal phes of paperboard) should be considered. It is generally desirable to minimize the amount of process water added with the adhesive or coating with sohd fiber products. Moisture trapped in the filler phes can result in pin holes or bhsters in the coating and/or warp of the sheet (15). 

Pigmented Coating Processes for Paper and Board, TAPPI Press BookNo. 28, Technical Association of the Pulp and Paper Industry, Atianta, Ga., 1962. 

Erodings of Slow-Releasing Core Tablets. The sustained-dose portion of a dmg is granulated with hydrophobic materials such as waxes, fatty acids, or fatty alcohols and compressed into a core. The initial dose is added to the core by a modified sugar coating process or by compression coating. Thus, a tablet within a tablet is created. The core erodes slowly to release the active ingredient. 

Both cold- and warm-coating processes employ solutions of phenoHc resins. The principal process used for foundry resins is the hot-coating process. It is the fastest, least expensive, and safest process, and it requires no volatile removal. The sand is heated to 135—170°C in a muller, and soHd novolak resin in flake form is added, which melts quickly and coats the sand. A lubricant may be added at this point. After one minute of mulling, the batch is cooled by adding water, which evaporates rapidly. 

The total cycle time for most production batches is 2.5—3.5 min, considerably shorter than the cold- or warm-coating processes. Although a few... 

Newer high velocity thermal spray coating processes produce coatings in compression rather than tension because of the shot peening effect of the supersonic particles on impact. This has permitted coating as thick as 12,500 p.m without delamination as compared to older processes limited to 1,250 p.m. The reduced residence time of particles at temperature minimises decomposition of carbides present in conventional d-c plasma. This improves wear and hardness (qv) properties. 

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