When paint is applied by brush, you must be sure that each coat is thoroughly worked with suitable brushes until a smooth, even coat is obtained, free from brush marks, laps, holidays, and drips of excess paint. You must make sure that the paint is worked thoroughly into all joints, cracks, and crevices, verify the coverage obtained and that the area covered per gallon is within acceptable limits. You must make certain that each coat is allowed to dry thoroughly before the next coat is applied and that the prescribed number of coats, each conforming to the requirements of the specifications, is applied. Nonferrous metal is usually not painted. When it is prescribed, you must prepare, prime, and paint the surfaces, as specified.

WOODWORK. - You must make sure that surfaces are thoroughly dry and clean and are otherwise suitably prepared for painting before permitting work to proceed. You must determine that the priming coat is intact and is of suitable consistency to protect the wood, but not so tight that moisture in the wood is prevented from evaporating. For exterior work, sandpapering will not be specified. You must be sure, however, that the wood is smooth enough to assure the continuity and adherence of the paint film; that holes and cracks are puttied or filled with wood filler; and that knots and pitch streaks are sealed with shellac, varnish, or other sealer, as prescribed.

You must be certain that the paints are of the specified type and quality; are mixed, colored, and thinned to provide a paint of uniform consistency and color; and are applied by brushing, using high-quality brushes, until the coat is smooth, even, free from brush marks, and of uniform thickness, texture, and color. Also, you must be sure that all cracks and crevices are sealed; that the paint is not brushed too thin to assure satisfactory hiding power; that each coat is allowed to dry thoroughly to a firm film before permitting application of the next coat; and that the specified number of coats is applied.

To stain shingles and trim, use either the dipping or the brushing method. You must be sure that, when dipped, the material is loosened so that the stain reaches all immersed surfaces; that it is left immersed until the stain has fully penetrated the grain; that excess stain is drained off; and that stain is replenished and stirred to assure uniformity.

Interior Painting

Paint for interior walls and ceilings is usually a flat wall paint. For small jobs the specifications may permit the use of approved commercial ready-mixed paints. Interior enamel may be specified where a semigloss or gloss washable finish is desired on woodwork or walls. The specifications may require either a standard undercoat for primer under enamel, or they may permit the use of the enamel with thinner. Paint and enamel may be obtained with color added, or color-in-oil may be added to the white paint on the job.

In general, requirements for inspection of interior painting are the same as those already described for exterior painting. Specifications may require the sanding of interior woodwork or rubbing with steel wool. Priming of plaster surfaces with a glue size may also be required. You must be sure that finish coats are of uniform gloss and color and are free from suction spots, highlights, brush marks, and other imperfections.

Special Work

Aluminum windows, doors, and trim usually will not be painted but will be given an alumilite or other anodic surface treatment at the factory. When painting is specified, it will be necessary to clean the surface thoroughly, so the surface is free from all dust, dirt, oil, and grease; to apply a primer of the type specified; and to apply one or more coats of paint, as required.

Where dissimilar metals are in contact, electrolysis may occur that uses the rapid corrosion of the anodic or positively charged material. Magnesium, zinc, and aluminum corrode when in contact with steel; steel and iron corrode when in contact with copper, brass, or bronze; and copper and its alloy corrode when in contact with the precious metals. Zinc coating protects steel at the expense of the zinc coating. You must be sure that aluminum is well-isolated from steel and that steel is well-isolated from copper by felt, varnish, or other methods, as specified. Cathodic protection by impressed current is another method of resisting galvanic action.

Before paint can be applied successfully to bright galvanized metal, the surface film must be removed and adequate tooth provided by treating the surface with diluted hydrochloric, phosphoric, or acetic acid. A 5 percent solution usually is specified. You must determine that the surface is completely treated and is then rinsed thoroughly with clean water. A small amount of lime sometimes is added to neutralize any residual acid. When dry, surfaces so treated are primed and painted like other metalwork. Refer to the Paint and Protective Coating manual, NAVFAC MO-110, for