GB1285417A - Production of protective coatings on metals by anodic oxidation - Google Patents

Abstract

1285417 Anodizing ruthenium layers; electrodeposition; sacrificial anodes INTERNATIONAL NICKEL Ltd 12 Oct 1970 [13 Oct 1969] 48407/70 Headings C7B and C7E An anode, for use in electro-plating, -winning and/or refining (e.g. of Cu, Ni, Mn, Cr), fused electrolyte, brine or other salt electrolysis (e.g. for producing Cl 2 ), catalytic electrosynthesis, fuel or battery cells, or for preventing corrosion (as a sacrificial anode), comprises a RuO x coating (average x preferably greater than 2) formed on an electrically conductive substrate, e. g. of Ti, Ta, Mo, Zr, Ag, Au, Pt group metal (Pt or Ru), Ni, Cu, Fe, Al, W, Zn, Pb or alloy thereof (Ni-Cr-Mo, stainless Ni-Cr steel, brass, bronze or of Ru), by applying an adherent Ru layer to the substrate, e.g. by chemical or vapour deposition, pressure or diffusion bonding, or electro-deposition from an aqueous acid Ru complex plating bath (prepared by heating aqueous RuCl 3 with excess sulphamic acid), and anodizing the layer in an aqueous electrolyte containing at least 0À01 mol/l KMnO 4 using at least one inert (e. g. Pt) cathode. The anodizing electrolyte may also contain at least 0.05 mol/1 K 2 Cr 2 O 7 . The oxide coating so formed is crack-free and may contain Mn. The substrate, preferably Ti or Ti alloy, may be a solid body e.g. strip, plate or sheet, or an expanded metal grid, a powder metallurgical compact or laminated composite, preferably plated with a layer of Ni or Au (e. g. from cyanide bath). The Ru layer may be heated in inert gas prior to anodizing. A Ti substrate may be prepared by degreasing and hot etching in HCl or HNO 3 + HF solution. The oxide coating may be heated at 500-800‹C. in air or oxygen containing atmosphere or argon. Alternatively, Ru oxide coated Ti formed as above may be used for compressor blades of turbine engines. Specification 1, 147,442 is referred to.