| 摘要 |
An article comprising a metallic base is protected against corrosion by electro-deposited layers of 1) Ni, 2) Ni containing Se and 3) Ni, the second layer being anodic to both the first and third layers. There may be a final electro-deposited layer 4) of Cr. Layer 1) may be 0.3-2 mil thick and contain 0-25% Co and less than 0.01% S. Layer 2) may be 0.01 to 0.2 mil thick and contain 0-25% Co and 0.1-10% Se. Layer 3) may be 0.15-1 mil thick and contain 0-50% Co and 0.03-0.3%S. Layer 4) may be 0.005-0.2 mil thick. The Ni electro-plating solutions contain at least one of nickel sulphate, chloride, fluoborate and sulphanate. Specified buffers are H3BO3, CH3COOH, borax, HCOOH and fluoborates. Brighteners may be included in some of the baths and brighteners of a first class (sulpho-oxygen compound) and a second class are specified (see below). Where the Ni is to be alloyed with Co, the Co may be included in the plating bath as a halide or sulphate. The Ni baths may contain wetting agents, e.g. anion surfactants of the sulphate type. Se may be added to the Ni baths in the form of selenic acid, selenous acid, Na, K, Co and Ni selenates and selenites or as organic compounds containing Se provided selenite or selenate ions are formed in solution. The substrate to be plated may be Fe, steel, Cu, brass, Al, Zn, Mg or alloys thereof with or without a Cu "strike" deposit. Each of the Ni layers may be deposited using more than one step, e.g. by interrupting the plating cycle. The brighteners of the first class include sulphonic acids, sulphonates, sulphonamides, sulphimides, sulphinic acid and sulphones comprising a ring derived from benzene, naphthalene, toluene, xylene, naphthylamine, toluidine, benzyl naphthylamine or a chain derived from vinyl or allyl compounds. The brighteners of the second class include ketones, gelatine, alkylenic carboxylic esters, alkylenic aldehydes, aryl aldehydes, sulphonated aryl aldehydes, allyl and vinyl substituted compounds, coumarin and its derivatives, acetylenic alcohols, nitrogen heterocyclics having an N-substituted acetylenic radical, azine-, thiazine-, and oxazine-dyes, triphenyl methane dyes, quinidines, pyrimidines, pyrazoles, imidazoles, pyridinium and quinolinium compounds, nitriles, thionitriles and compounds having the thioureide radical (N-C=S). |
