| 摘要 |
An aqueous liquid chromate free primary composition for forming a protective coating on metals, particularly aluminum, is made by reacting cobalt(II) cations, carboxylate anions, at least one other type of coordinate complexing agent for cobalt(III) cations, and an oxidizing agent in an aqueous solution in which the molar ratio of carboxylate anions to cobalt(II) cations is from 0.10 to 6.8 and the aqueous solution contains no more than 1% of each of ammonia, ammonium ions, and nitrite ions. The primary layer formed by this or any other composition that forms a coating containing metal atoms and oxygen atoms on a metal substrate is advantageously sealed by further treatment with an aqueous solution of sodium ammonium decavanadate, optionally after an intermediate step of immersing in water for a few minutes between the primary treatment and the sealing treatment. |
