Makoto Kumada

A Few Examples of Localized Corrosion Problems and Their Countermeasures in Chemical Plants

Classification of the case histories of 965 encountered for last eleven years made clear that more than 30% of failures were caused by corrosion and that 98% of those were owing to localized corrosion such as pitting and stress corrosion cracking. Localized corrosion failures often results in considerable economic loss and disaster. This paper describes a few cases of localized corrosion and preventive studies which were conducted in order to improve structure, material and environment. The first case is pitting corrosion of a stainless steel strainer in the purification plant of waste water using active carbon. Active carbon promoted the occurrence of pitting corrosion. The design modification of structure and cleaning of the strainer was employed as a countermeasure. The second case is stress corrosion cracking which originated from corrosion pits under small deposits in a reactor made of austenitic stainless steel. From the results of plant tests, material of the reactor was changed from austenitic stainless steels to titanium. The third case is stress corrosion cracking which occurred around weld zone of SUS 316L in a distillation plant. The same material was used for the new fabricated plant, while stress corrosion cracking was prevented by solution heat treatment using large furnace.