Method of and apparatus for plating a surface of a web

摘要

A web is coated electrolessly with a layer of metal and is then electroplated by passing it sucessively through two separate electrolyte baths, the first bath containing a cathode and the second bath an anode with the web forming the only electrical connection between the baths so that plating occurs in the second bath. Typically the electroplated web is passed through a third bath containing mercury arranged to serve as a cathode and if desired a further mercury cathode bath may be provided so that the plated web can be given a further electroplating by passage into a plating bath between the mercury baths. Typically the first electrolyte bath 10 and the mercury baths 51, 52 are situated in but insulated from the plating electrolyte 12 in the bath 13. The electroless plated web 11a is passed by rollers of stainless steel, glass, ceramic, P.T.F.E. or other insulating plastic through the baths 10, 51, 52 with intermediate descents into the bath 13 in which are arranged pairs of plate anodes 24a-24h, plating occuring when the web is adjacent these anodes. Before and after passage through the mercury 63 the web is passed through a cleaning liquid lying over the mercury. If desired instead of cathode plates 20, 62 the baths 10, 51, 52 may be of metal with outer insulated coatings and connected directly as cathodes. With lateral extensions on the cathode plates 20 in the bath 10, deplating of the electroless coating occurs on the edges of the web 11b. Plating may be effected on only one face of the web if the web edges are deplated by using insulating immersed guide rollers 14b, 14g, 14l and causing the axes of these rollers to lie above the level of the electrolyte and mercury in the baths by controlling the liquid levels. Provision is also made for regenerating the electrolyte of bath 10 and for continuously removing contaminants which collect in the wash water in baths 51, 52. The bath 10 may contain the same electrolyte as the plating bath 13 and is preferably of pH 1-4. The electroplating may be of cobalt or cobalt-nickel for forming a magnetic recording tape and different electroplated thicknesses may be obtained on opposite faces of the web by applying different potentials to each of the anodes of a pair, as 24b, 24c, 24f, 24g relative to 24a, 24d, 24e, 24h. Specifications 989,563, 1,013,673 and 1,013,674 are referred to.