Experimental Procedures
Metal samples were removed from the systems and were examined visually and under a stereomicroscope. The chemical compositions of the pipe material and the weld metal were analysed with an optical emission spectrometer (OES). Metallurgical examinations consisted of optical light microscopy of cross sections prepared from the samples, scanning electron microscopy (SEM) studies from failure areas and energy dispersive spectroscopy (EDS) of corrosion products or of the deposits on the inner surfaces of the pipes. In Case 1, the metal samples were completely dry when arriving at the laboratory. Therefore, traditional methods like cultivation could not be applied to detect possible bacteria. However, preliminary trials with a new PCR method were performed with one sample showing corrosion failure.