Susceptibility to Stress Corrosion and Crack Initiation and Propagation of 7A04 Aluminum Alloys

Abstract

The crack initiation and propagation of 7A04 aluminum alloy in 3.5%NaCl solution at pH=1,4,7,12 during slow strain rate test (SSRT) were investigated by the method of combining phase shift with electrochemical impedance spectroscopy. The feasibility of the method was verified by electrochemical noise (EN). The results show that the more corrosive the solution is, the susceptibility of the 7A04 aluminum alloy to stress corrosion cracking is greater;in the solution at pH=1,the phase shift method shows that crack initiates at 1h and propagates at 4.5h,and the electrochemical impedance spectroscopy in situ method shows the crack initiation and propagation are discontinuous,and in stages;the EN results show that the crack initiation occurs at a certain moment among 3000-5000s and propagates obviously at a certain moment among 13500-22500s accompanying with obvious periodical current and potential noise peaks.

Keywords

• aluminum alloy
• stress corrosion cracking
• electrochemical impedance spectroscopy
• electrochemical noise