Abstract: Dissimilar steel is used to weld the connection between the preheating pipe segment of cracking raw materials and the preheating coil. In the production process, corrosion leakage occurs successively in the cracking furnace for light hydrocarbon medium. In order to find out the causes of pipeline corrosion failure and leakage and to solve the problem completely, the failure analysis of the pipeline section where leakage occurs is carried out through macroscopic inspection, chemical composition analysis, hardness test and microscopic electron microscope scanning combining with the composition of corrosion products. According to the analysis, the galvanic corrosion of dissimilar steel formed in this pipe section due to changes in working conditions during the production process was the root cause of the corrosion leakage. Aiming at the above causes, corresponding solutions were proposed and these methods were adopted to improve three of the cracking furnaces. At present, the three cracking furnaces are operating well and no further corrosion leakage have been detected.

Key words: cracking furnace, convection section, corrosion, leakage