Chapter 9 - Electrocorrosion Protection of Metals in Electrochemical Plants Based on Existing Methods

Abstract

This chapter focuses on methods and means of electrocorrosion protection of metals in electrochemical plants. Rubber linings and some other kinds of lining belonging to nonporous coatings are able to work without destruction for a relatively long time. For example, a fairly positive effect was experienced using chlorine-resistant linings, such as ebonite, in chlor-alkali plants. Ebonite produced on the basis of chloroprene rubber is the most stable in the environments of these plants. Rubber linings have been used for many years for the protection of pipelines, electrolyzer covers, and other equipment. Large-size equipment was protected by linings with an underlayer of ebonite or of another polymer material and 2–3 layers of diabase tiles. Although the problem of selecting accessible, reliable, and stable isolating materials for the highly aggressive environment of electrochemical plants has not found a conclusive solution until now, using these protective materials still remains attractive. This is explained by the comparatively low cost of this protection and by the possibility of the anticorrosion crews of the electrochemical plants executing such protection themselves. Reduction of the external current acting on the metallic structure is usually regarded as a means of diminishing, but not of preventing, the corrosive destruction of the metal. In fact, when a metal corrodes in an active state, the corrosion rate is proportional to the magnitude of the external anodic current, i.e., the lower the current, the lower the corrosion rate. Moreover, reducing the external current acting on the passive metals may, in some cases, completely prevent the corrosion failure.