This article is a sub section from the transcripts of "Working with an Artist Blacksmith" - originally published in hard copy by BABA - the British Artist Blacksmith Association.

Materials such as stainless steels, bronzes and brasses may be left unpainted. Bronze and brass will develop a natural patina, darkening with age, Mild steel and wrought iron require some form of protective coating to inhibit rusting. For interior use, it may be sufficient to oil or wax the metal. The black iron oxide helps to hold the oil or wax. This kind of finish has been traditionally applied to interior items and has the great benefit of enhancing the surface of the metal. figured by the hammer blows which shaped it.

For exterior purposes some form of paint finish is essential. As with all painted surfaces, preparation is critical, and at the very least forged metal requires vigorous wire brushing to remove all traces of loose oxide before priming and painting.

A number of phosphate based or zinc rich paints are available to provide an inhibiting primer coat. Better still, is to prepare the surface by blast cleaning employing beads or shot which will totally remove scale from accessible surfaces, and provide an excellent key for the primer paint.

For a higher level of corrosion protection, it is preferable to galvanize or zinc spray the metal prior to priming and painting. Both processes coat the metal with a thin skin of metallic zinc which electrolytically protects the iron or steel underneath. The choice depends on availability and the design of the metalwork. Zinc spraying after shot blasting offers excellent protection, so long as there are no inaccessible crevices which the spray cannot reach. The porous sprayed metal surface provides a good key for immediate painting.

Galvanizing involves the chemical stripping of the metal in an acid bath. followed by immersion in a tank of molten zinc. The size of the available tank provides a limit to the size of assembly which may be treated. The nature of the process ensures good penetration into crevices. The galvanized surface needs weathering or special etch priming before painting. Both zinc coating processes add to the first cost of the item, but will very considerably reduce maintenance costs over a period of time.

The worked surface of the metal is a very important characteristic of forged work, but this can be lost by inappropriate paint finishing. Eggshell or semi-matt finishes are preferable to matt or gloss. Better still are "highlighted" finishes using a lighter color dragged over a darker finish, micaceous iron oxide paints or paints loaded with flake graphite powder which may be burnished as they dry, to produce a surface similar to the black sheen of bare forged iron.

Author: Peter Parkinson

ArtMetal Editor/Curator: enrique

Last Updated: Tue, Nov 14, 1995