Platinum as a Metallic Material
Examples of Applications in the Glass Industry
Components and equipment of ceramic refractory materials are adequate for the manufacture and processing of normal glass qualities. However, the ceramics are slowly attacked by the molten glass which can lead both to striae in the glass and to a change in the dimensions of the components. The attack of the refractories becomes more severe at high temperatures such as are encountered in the production of high strength glass qualities and in the refining of glasses for optical applications. In all areas in which the erosion of the refractory materials cannot be tolerated, the ceramic components are clad with platinum materials or the complete component is made from a platinum material, because platinum and rhodium are the only metals that are resistant both to oxidation in air and to the corrosive attack of the molten glass. Components that are subjected to high mechanical loads, such as stirrers, are made from the refractory metal molybdenum which is protected against oxidation by means of a cladding of a platinum material. The most commonly used platinum materials are alloys of platinum with 10-20 % rhodium. Components that are made completely of the precious metal have the added advantage that they can be resistively heated by directly applying an electrical current.