Anodic protection of 316L stainless steel piping in sulfuric acid service: failure causes and remedial actions

Abstract Anodic protection (AP) is one of the corrosion control methods that has been widely used in the manufacture, storage, and transport of sulfuric acid. The present paper gives a brief review of the history, some applications, and a case study of failure causes and remedial actions of AP in a sulfuric manufacturing plant. The AP system consists of a direct current source, cathodes, reference electrodes, and signal conditioning electronics. In a sulfuric manufacturing plant, for AP of 316L piping (as an anode), platinized titanium (Pt/Ti) and Hastelloy B-2 were used as reference and cathode electrodes, respectively. After seven years of operation of the AP system in the sulfuric acid plant, a section of the protected pipelines has severely corroded. The study of the system showed that the reference electrodes, which were titanium-electroplated with platinum, lost their stability in the acid with the loss of coating and caused overprotection. However, the system could not control the pipe’s potential in the AP situation. In this condition, accelerated corrosion of the cathodes and pipes has also occurred.