with lead products, oxides of iron, carbon, or any hard, indifferent powder.

Zinc Chromate

The only use made of this pigment in structural iron paints is as an inhibitive of corrosion. Being a double chromate of zinc and potassium, and somewhat soluble, it acts, when pure, like potassium chromate in preventing rust. Some other chromates, such as calcium and barium chromates, have the same power.

The use of inhibitive chromates is yet very small, partly, no doubt, because their actual utility has not been proved by endurance tests, and partly because the use of any quality short of chemically pure is worse than useless, since the impurities may be stronger stimulators of corrosion than the zinc chromate is an inhibitor.