Some recent developments in protective coatings in U.K

The Batch Type aluminising process, a modification of the BIRSA Glycerol process, has already been taken up for industrial production of aluminised sheets. Hot-dip galvanising by the batch process has a few drawbacks, namely, brittle and uneven coating, excessive dross formation and loss of ductility due to strain ageing. The Sendzimir process has overcome some of these defects with methods of surface preparation and spelter composition that can be constantly controlled. Continuous electro-tinning from the sulphonate bath results in increased production with conservation of tin and ensures uniform coating of low porosity, superior corrosion resistance and relative ease of operation. Electrolytic galvanising is another achievement of recent years capable of further protection against under-film corrosion. In the field of metallisation, stainless steel coating, dual coatings, coatings for protection against high temperature oxidation and replacement of worn parts by spraying have been widely developed. Plastic coating of steel sheets, although a new comer in the field, appears more promising for further development. (Mr. A.N. Kapoor, Senior Scientific Officer, National Metallurgical Laboratory, Jamshedpur)