A Systematic Scheme for Examining CORRODED METAL SPECIMENS

Many corrosion problems have to be investigated by post mortem examination, and it is often through the medium of such investigations that valuable progress has been made in the understanding of corrosion processes. To quote but one example—one form of corrosion of copper tube, which very occasionally occurs in domestic water and which, more often than not, used to be ascribed rather vaguely to ‘deposit attack,’ was eventually explained, after three or four years of intensive laboratory work, to the conjoint existence of a discontinuous cathodic film on the metal and the lack of natural inhibitor in the water. The first tangible clues to the solution of this problem, in fact, first became evident from a painstaking examination of failed specimens. To obtain sufficient evidence to explain a corrosion failure often involves the use of such diverse techniques as micro‐chemical analysis, x‐ray examination and metallography, and the principal object of this article is to describe in detail the way in which such techniques are employed.