Correlation Between Microstructure and Corrosion Behavior of Two 90Cu10Ni Alloy Tubes

Abstract

Two kinds of 90Cu10Ni tubes with different service lives (more than 3 years and only 1 year, respectively) under identical working conditions were studied by an immersion test in a 3.5 wt% NaCl solution and the electron backscattered diffraction (EBSD) technique. The morphology after immersion showed severer corrosion attack at the grain boundaries of the tube with shorter service life compared with the tube with longer service life. The grain boundary characterization distributions (GBCDs) of the two tubes obtained by EBSD revealed more Σ3 boundaries and twins, and larger random boundary meshes in the tube with longer service life. A short immersion test in a modified Livingston’s solution was conducted to evaluate the tendency to corrosion attack of different types of the grain boundaries. SEM and AFM were used to characterize the corrosion morphologies of the boundaries. A strong correlation between varying depths of corrosion grooves and types of the grain boundaries was obtained. The influence of deviation angle of low Σ boundaries on corrosion resistance of the grain boundaries was also discussed. It is concluded that a special “grain boundary engineering” (GBE) treatment has been performed on the tube with longer service life. It is proposed that the optimized GBCD is responsible for the better service performance of the tube.