Abstract: A method of producing an article comprises applying a non-ferrous metal layer on a substrate and protecting metal layer by applying thereto a compound having a nitrogen atom which is linked to the remainder of the compound by three single bonds and which has an accessible electron lone pair, such that the electron lone pair bonds to the metal to form a complex which is insoluble or substantially insoluble in water and which protects the metal layer. The compound is preferably 1,4-Diazobicyclo (2,2,2) octane. The method is of particular use in the production of mirrors comprising a transparent substrate on which is deposited a silver layer followed by a copper layer, the compound being bonded to the copper layer by formation of the complex. The invention also provides an article made according to the method described above.