Platinum Metals Rev., 1970, 14, (1), 20
Spot Welding Platinum Foil on Titanium Anodes
Titanium anodes coated with platinum are used in many cathodic protection applications. Electrodeposited platinum is usually only a few micro-metres thick but for certain processes there is a platinum loss which calls for a layer of greater thickness. Hence, for example, platinum foil is used on the anodes that protect the drying cylinders of paper-making machines against the corrosive effect of the cooling sea water (1). For anodes used in this way, foil is cheaper per unit weight than electrodeposited platinum and the platinum loss is much less.
A. Baggerud of the Technical University of Norway reports (2) that spot welding of platinum foil to titanium has produced anodes which have protected drying cylinders successfully over several years. The method is reliable and no selective corrosion of the foil at the spot welds has occurred.
Baggerud has developed specifications for 30 and 50μm foils and tolerance limits for the welding current have been determined. Melting of the platinum foils must be minimised during welding lest magneto-hydrodynamic effects cause the formation of brittle intermetallic compounds. Oxides on the titanium surface have little effect on weldability and the Peltier effect is no real hindrance.
- 1A. Almar-Neiss and J. Drugli, Platinum Metals Rev ., 1966, 10, (2), 48 51
- 2A. Baggerud, Metal Construction, 1969, 1, 412