THE economic and mechanical advantages which result from the use of the steels and cast irons are so important that, despite their low resistance to corrosion, they are used more extensively than all other metals put together. The inevitable result of this is an enormous wastage, resulting in the expenses of replacements and, even more, of the necessity of their protection by greasing, painting, etc. Sir Robert Hadfield has estimated that the annual cost throughout the world due to corrosion amounts to more than £500,000,000. Sir Harold Carpenter, in a lecture delivered before the Royal Society of Arts (Jour. Boy. Soc. Arts, May 8, 1931), reviewed the whole question of stainless metals, mainly ferrous ones, both from a fundamental and from the technical points of view.