Corrosion studies on Cu-based alloys

Abstract

Cu-based alloys are widely applied in corrosive environments. The improvement of the alloys' corrosion resistance will significantly reduce energy consumption and overexploitation of resources. To increase the resistance of copper as less corrosion alloy component, nine imidazole-based compounds with different functional groups were tested as potential corrosion inhibitors. Besides, CuZn alloys, CuZr crystalline and amorphous alloys, and their pure metals are tested to explore the correlations between inhibition and structure and elements. For CuZn alloys, the α-Cu phase Cu70Zn30 (at.%) alloy and non-α-Cu phase Cu30Zn70 (at.%) alloy were tested. CuZr alloys are the basis of a family of metallic glasses with large glass-forming ability and remarkable mechanical properties. The corrosion response of as-produced crystalline and amorphous CuxZr100 −x alloys (x = 40, 50, 64 at. %) were tested. The alloys were immersed in 3 wt.% NaCl aqueous solution. Potentiodynamic polarization measurements, electrochemical impedance spectroscopy and long-term immersion tests followed by microscopy analysis and Raman spectroscopic analysis were carried out. Comparative analysis of pure Cu and Cu70Zn30 (at.%) alloy shows that the same inhibitors are effective in both alloys. Similar behavior is found with pure Zn and Cu30Zn70 (at.%) alloy. However, the inhibition power shows a different value, which should be attributed to the patch effect. Defects present in most of the polished samples accelerate the pitting on these locations. The patch effect will lead to a patch on those positions, which will slow down the local attacks. All tested amorphous alloys show much better corrosion resistance than their crystalline counterparts in the presence and absence of inhibitors. All tested amorphous alloys show much better corrosion resistance than their crystalline counterparts in the presence and absence of inhibitors. The main factor controlling the corrosion resistance of the alloys appears to be the Zr-rich (or at least equiatomic) amorphous structure, the effect of the inhibitors being secondary. Results, therefore, show a complicated relationship between inhibitor performance, microstructure and composition of CuZr alloys. SH-ImiH-4Ph shows potential to become a global α-Cu phase alloy inhibitor and SH-BimH-5NH2 shows potential for Zn-based and CuZr alloys. Electrochemical measurements, especially longterm measurements, display a significant correlation to immersion tests.