Priming coats

Poly(vinyl acetate) emulsions are used to prime-coat fabrics to improve the adhesion of subsequent coatings or to make them adhere better to plastic film. Plasticized emulsions are appHed, generally by roUer-coating, to the backs of finished mgs and carpets to bind the tufts in place and to impart stiffness and hand. For upholstery fabrics woven from colored yams, PVAc emulsions may be used to bind the tufts of pile fabrics or to prevent sHppage of synthetic yams. 

Enamel coatings usually consist of several layers in which the prime coating is applied for adhesion but does not have the chemical stability of the outer layers. With cathodic polarization at holidays, attack on the exposed prime coating is possible as the cathodically produced alkali causes the defects to increase in size. This particularly cannot be excluded in salt-rich media. 

Application of protective paints consists of surface preparation of steel, priming coat and finishing coats. Wherever possible, steel should be blast-cleaned before painting. Primers thoroughly wet the metal to promote adhesion of finishing paints and carry inhibitive pigments. For example, red lead oxide will minimize the spread of rust on metal surfaces. The total thickness of fmishing coats must be at least 0.125 mm for adequate protection and life. Four coats of paint usually are necessary to achieve this. 

In all cases a priming coat of paint containing some form of hexavalent chromium such as zinc or strontium chromate should be used. 

The priming coat provides the bond between the metal and subsequent coats. It gives electrochemical control of corrosion. Adhesion is dependent largely on the nature of the binder and the cleanliness of the metal surface. 

For previously painted and fireproofed surfaces, the mastic manufacturer should be consulted to assure compatibility with the existing surface, proposed paint primer, and mastic. New galvanized surfaces should be mechanically abraded to ensure adherence of the prime coating. 

The shape is generally similar to the shape of a storage canister or dispenser from which the decoy flare is ejected by the aircraft upon command of the pilot. The decoy body generally has a circular or rectangular cross-section because of the cost considerations and ease of manufacture. The shaped flare is covered with a priming coat that facilitates ignition when the decoy is released from the aircraft. 

Red lead (Pb304) has a brilliant red-orange color, is quite resistant to light, and finds extensive use as a priming coat for structural steel because it possesses corrosion-inhibiting properties. 

Zinc chromate (ZnCr04), also known as zinc yellow (with the approximate formula 4Zn0K204Cr03-3H20), is used as a pigment because of its excellent corrosion-inhibiting effect both in mixed paints and as a priming coat for steel and aluminum. 

The histidine-rich sheath seems to act as a priming coat for distribution of intensely osmiophilic globules 49, 64). This osmiophilic matrix or cementing substance is probably sulfur-rich 64, 82) and has been observed as patchy deposits 49) that embed the 100-A filaments within 250-A fibrils 64, 70). Various evidence suggests that this osmiophilic... 

The emission factor on a solids basis, EF, for the prime coat (p) is... 

Use Component of structural-metal priming coat paints, rust-inhibitor in paints, lubricants, vinyl plastics, and rubber products. 

All the tunnels were founded on or in the shattered basalt. Most of the tunnel footage was placed in trench-type (open) excavations. Backfill consisted of a mixture of the two upper strata, with embedded rock fragments in some areas, compacted to 90% to 95% modified AASHO maximum density. Waterproofing provisions included external membranes at the junctions of tunnels with other facilities, lead washers for all tunnel bolts, welding of all laps, and, on the exterior tunnel surface, a -in.-thick asbestos-fibered asphalt mastic placed on an asphalt prime coat. 

The metal oxide supports can be oxidized to produce either a catalytic coating or an anchor for added catalytic components. The use of a ceramic prime coating is not particularly suitable because of spalling. 

Nowadays the most commonly used enamels are synthetic resins, e.g. vinyls, acrylics, epoxy resins, which are usually stoved after application. Sometimes a priming coat is applied before the base coat to facilitate subsequent forming operations. 

Undercoat- A coating applied prior to the finishing or top coats of a paint job. It may be the first of two or the second of three coats. Sometimes called the Prime coat. 

Typically at least two slurries are used. The first of these is called the face coat or prime coat slurry. It is made up of very fine ceramic flour usually 200 mesh or finer. This slurry is the first slurry the wax patterns are dipped into and the very fine texture is required to faithfully replicate the fine details of the pattern. It is also the surface that the molten metal comes in contact with, when it is poured into the mold. Because of this, it is very important that the ceramic selected for this first or prime layer be inert chemically to the molten metal being poured. If not, the molten metal will react with the ceramic and lose its desirable metallic character. 

The prime coat of refractory on the wax is usually only about 0.010-0.025 in. thick and is not strong enough by itself to support the load of the molten metal being poured. It is dried and then additional layers of slurry are added, stuccoed, and dried. Usually no more than two prime coats of very fine refractory are used. The rest of the shell is made up of back-up coats. 

---