Effects of trace La addition on corrosion properties of oxygen‐free copper tube in a formic acid environment

Abstract Oxygen‐free copper (OFC) tubes are widely used in heat‐transfer units. Due to the thickness of the OFC tube wall becoming thinner and thinner, higher demands are put forward for its corrosion resistance properties. We investigated the effects of trace La addition on the corrosion properties of OFC tubes in a formic acid environment through experiments of vapor corrosion and electrochemical corrosion. Although a small number of La would exist on the grain boundaries of copper tubes, there was no apparent influence on the grain size of OFC tubes. In HCOOH vapor, La addition increased the compactness of corrosion product films, decreased the size of corrosion pits, and improved the corrosion properties of OFC tube. Furthermore, rare earth La purified copper matrix, decreased the cathode area of impurities and inhibited the cathode reaction. Electrochemical corrosion resistance properties of the OFC tube were improved by the addition of trace La.