Black conversion coating compsn. - for nickel deposits contains chromate and nitrate ions

摘要

A compsn., for forming a conversion layer on a nickel deposit, contains chromate ions and nitrate ions, pref. together with phosphate ions and sulphate ions. A black nickel deposit is produced by depositing nickel on an article and then forming a conversion layer by treatment with an aq. compsn. contg. chromate and nitratee ions while the article is connected as an electrode supplied with periodically reversed current.