Painting Metal

Painting Structural Metal.

By structural metal we commonly mean steel and cast iron; wrought iron is rarely used, and is more durable than steel. Cast iron is much less liable to rust than steel; and as it is thicker, there is less danger of its total destruction. Steel, if not properly cared for, perishes more rapidly than wood; and it is therefore imperative that it should receive adequate protection.

In the first place, the surface must be clean. If it is already rusty, do not paint over the existing rust; clean it off with steel scrapers, wire brushes, and finally with dry scrubbing brushes. It would be better if it could be made absolutely clean by the use of acid or the sand blast, but the steel used in houses is not likely to be treated in this way. But do not spare labor to get it as clean as possible; then the paint will stick to the metal. As the oil does not soak into the surface, it is not necessary to have a thin paint, but it may receive three coats of some good paint. Graphite is largely used as a pigment for these paints; there are some varnish paints and varnish-like preparations which are good; red lead mixed with linseed oil, in the proportion of eighteen to twenty-four pounds of pigment to a gallon of oil, mixed on the spot and immediately before using, is very much liked. It makes a good under-coat; its color and working qualities may be improved by adding lampblack; and it should be covered by a coat of some other paint.

Whatever paint is used should be well brushed on to the surface of the metal, in order to remove, as much as possible, the film of air which tends to prevent perfect adhesion, and any crevices where the steel is riveted should receive special attention. The rust usually appears first on edges, angles, and rivet and bolt heads; care should be taken that these receive full coats of paint. Slow-drying paints should be used on structural metal, and plenty of time to dry should elapse between coats.

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