High-Temperature Corrosion Behavior of Cu-Al Binary Alloys

• Main Authors: Gan-Wei Fan, 范綱維
• Other Authors: Wu Kai
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/68862306719255935466

碩士 === 國立海洋大學 === 材料工程研究所 === 91 === The purpose of this thesis is to study the corrosion behavior of Cu-Al binary alloys (containing Cu-1, 5, and 10 Al, all in wt.%) over the temperature range 500~900oC in H2/H2S and H2/H2S/H2O mixed gases and at 900oC in dry air. At different S2-bearing environments, the sulfidation kinetics of all Cu-Al binary alloys followed the parabolic rate law at all temperatures, and the corrosion rate constants decreased with increasing Al content. The scales formed in H2/H2S mixed gases on the three alloys were duplex and heterophasic, consisting of the outer layer of mostly Cu2S, and the inner layer of heterophasic mixture of mostly CuAlS2 and minor Cu2S. In addition, the substrate beneath the inner layer of the Cu-5Al alloy was transformed to Cu3Al and Cu9Al4, and of the Cu-10Al alloy was transformed to Cu3Al, indicating that matix phase-transformation was taken place on both Cu-5Al and Cu-10Al. The scales formed on all alloys in the H2/H2S/H2O gas mixture were similar to those of in H2/H2S mixed gases, indicating that the partial pressure of oxygen is too low to form stable oxides. Platinum markers were always located at the interface between the inner and outer scales, suggesting that the outer scale grew by outward transport of copper and the inner scale grew by the inward diffusion of sulfur. The oxidation kinetics of all Cu-Al based alloys also followed the parabolic rate law at 900oC, and the oxidation rate constants decreased with increasing Al content. The oxide scales formed on Cu-1Al consisted of only CuO, while mostly CuAl2O4 and a small amount of CuO was detected on Cu-5Al. The oxide scale formed on the Cu-10Al alloy was exclusive α-Al2O3.