Effects of cathodic polarization on SCC behavior of AA7003 under various aging treatments

Abstract

In this paper, the effect of cathodic polarization on corrosion behavior of AA7003 under three kinds of aging treatments (including peak aging (PA), double peak aging (DPA) and regression re-aging (RRA)) was studied in 3.5 wt% sodium chloride solution through slow strain rate testing(SSRT) and electrochemical testing. X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods were also applied to investigating corrosion behavior and fracture morphology. The results showed that under open circuit, stress corrosion cracking (SCC) of AA7003 might by classified as anodic dissolution. In this case, the extent of SCC susceptibility (I_SCC) of AA7003 alloy with different aging treatments was as follows: I_SCC(PA)>I_SCC(DPA)>I_SCC(RRA). On the other hand, stress corrosion cracking (SCC) of AA7003 under cathodic polarization might be classified as hydrogen embrittlement (HE) which had been proved in this paper by presence of AlH3 diffraction peak in XRD patterns. In this case, for AA7003 with any of the three aging treatments, hydrogen embrittlement susceptibility (I_HE) increases with negatively shifting of cathodic polarization.

Keywords

7003 aluminum alloy / aging / stress corrosion / cathodic polarization / hydrogen embrittlement

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