The formation of a very thin blue oxide film on steel either by heating in air or by immersion in concentrated oxidizing solutions.
A method of coating sheets with a thin, even film of bluish black oxide. The blued surface is obtained by exposure to an atmosphere of dry steam or air at a temperature of about 1000°F. Generally this is done during box annealing.
An oxidized blue surface on plate armour, produced through heat treatment.
A mould blemish in the form of a blue oxide film which occurs on the polished surface of a mould as a result of the sue of abnormally high mould temperatures.