The Laser Raman Microprobe — A New Technique for the Identification of Corrosion Scale Constituents

The effectiveness of a laser Raman microprobe, with a two micron spot size and 1–2 micron probe depth, to provide microcompositional information about corrosion scales has been assessed by the examination of 20%Cr/25%Ni/Nb and 20%Cr/25%Ni/Nb + 0.13%Ce stainless steels oxidised in carbon dioxide based gases. For the first time it has proved possible to establish the unidirectional variation in the constituent phases of a thin (≤ 1 micron) oxide scale and also to identify precisely the nature of the oxide layers comprising thicker (≥ 8 micron) scales.