Chapter 4 - Using Structures of Metallic Materials in Electrochemical Plants without Taking into Account Attack by Leakage Currents

Abstract

This chapter discusses the application of metallic materials in electrochemical plants without taking into account attack by leakage currents. The traditional structural metallic materials, carbon and stainless steels, are applied in media where they are able to maintain their passive state in the absence of attack by leakage currents. In most cases, attack by anodic leakage currents is the cause of corrosion failure of piping and other structures made of these metals. Besides this, in some cases (e.g., nickel in alkaline media under the conditions of water electrolysis, stainless steel 18-10 in the electrochemical production of perborates) the metal is able to maintain its corrosion stability in the zone of leakage current action. Titanium played an important part in the technical progress of electrochemical plants. The commercial use of titanium as a structural material in aggressive environments of the chemical, metallurgical, and other branches of industry deserves special consideration, owing to the ability of titanium to maintain its corrosion stability. Thus the most crucial equipment at all stages of the technological processes, from preparing and feeding of the electrolyte, and up to the lines of industrial waste, was made of this material. Titanium piping and equipment in copper electrorefining plants are also susceptible to corrosion by external anodic currents. As in other kinds of electrochemical plants, corrosion damage was noted in the areas of metallic pipes joined to the pipes of nonconductive materials and at the terminal areas of the pipes where jets of electrolyte were flowing out.