Galvanized iron should not be painted until it has been exposed to the weather for a year as paint adheres badly to new galvanized iron. If necessary to paint sooner, a coat composed of about 200 grams of copper acetate added to 5 liters of water, or 60 grams of muriatic acid added to a mixture of 60 grams each of copper chloride, copper nitrate and sal-ammoniac, dissolved in 5 liters of soft water, to which a small quantity of hydrochloric acid has been added, should be given. This is sometimes called Mordant solution. This mixture turns the galvanized iron black; the treated surface should be left for at least 12 hours before being painted. This will be sufficient for about 250 sq.m of the surface. Over this a priming coat of red lead mixed with linseed oil and turpentine in equal proportions is applied. Ready-made paints are also available for this purpose. It is considered that paint will adhere to galvanized iron if the surface is washed with vinegar or slaked lime and washing soda before painting. Zinc white does not adhere to galvanized iron.
