A method of Flattening and Polishing Finely Divided Metal Particles

1,183,379. Making metal flakes. E. T. CLAYTON. 19 April, 1967 [22 April, 1966], No. 17943/67. Heading B3A. [Also in Division C3] Finely divided particles of metal not higher than zinc in the electro-chemical series are flattened and polished to form flakes by subjecting the particles to mechanical flattening forces in the presence of an aqueous medium containing a polishing agent and a flux to remove oxides from the surface of the particles or containing a material which acts both as a polishing agent and flux. The particles are polished and flattened in a ball mill in the presence of a weldment inhibitor if the particles are prone to adhere to one another. Defoamers, buffers, mica grinding agents to reduce the size of the flakes and detergents acting as wetting agents may be optionally added to the ball mill. Several examples of suitable polishing agents, fluxes and weldment inhibitors are given. At least 75% of the metal particles produced are minus 100 mesh and at least 50% minus 200 mesh. The flakes may be encapsulated with a second metal, e.g. zinc encased copper or copper encased zinc, by ball milling without a weldment inhibitor. The particles may be of Zn, Sn, Cd, Pb, Au, Ag, Cu, Ti, brass, stainless steel, bronze and aluminium bronze.