An investigation of the comparative resistance to corrosion of condenser tubes of different materials was carried out both under laboratory and operational conditions. The method of conducting corrosion tests in the laboratory has been previously described. The resistance to corrosion of spirally grooved profiled tubes was investigated, the tubes having worked under various operational conditions at thermal power stations for 8 years; the investigation was conducted by X-ray spectral examination of surface layers of the tubes (up to 70 mu m) with the aid of a microanalyzer. Error in determining contents of the components in the tube alloys did not exceed 0. 05%.