EVALUATING THE CORROSION RESISTANCE OF WELDED JOINTS IN GAS AND OIL TRANSMISSION PIPES.

The examined welded joints represent a complicated multi-electrode system with the characteristic electrodes being the weld (cathode) and HAZ (anode). The depth of corrosion damage in the HAZ is considerably greater than in the weld metal. Heat treatment of the welded joint makes it possible to reduce the depth of corrosion damage and alter at the same time the type of corrosion: concentrated corrosion appears on the background of uniform corrosion. The zone of the welded joint in the area of transition of the weld metal to HAZ with a coarse-grained nonequiaxed structure of the Widmanstaetten type with areas of quenched structures has high corrosion resistance.