二级时效应力对7A04铝合金电化学腐蚀行为的影响

Effects of Aging Stress on Electrochemical Corrosion Resistance of an 7A04 Al Alloy with Two-stage Stress Aging

采用极化曲线和电化学阻抗谱法,研究了在3.5%的NaCl溶液中二级时效应力对Al-Zn-Mg-Cu铝合金(7A04)电化学腐蚀特性的影响。结果表明,在0~300MPa二级时效应力内,随着应力增加,7A04铝合金的腐蚀电位先增加后降低,自腐蚀电流先减小后增大,在200MPa时其耐电化学腐蚀性能最佳,对应腐蚀电位和自腐蚀电流密度分别为-0.753V和5.249×10^(-7)A·cm^(-2);与无应力和单级应力时效相比,7A04铝合金二级应力时效后的腐蚀电位和交流阻抗更高,自腐蚀电流更小,但其对点蚀电位影响不显著。7A04铝合金应力时效后析出相分布和尺寸的改变是其耐电化学腐蚀性能提高的主要因素。

The effects of secondary aging stress on electrochemical corrosion of Al-Zn-Mg-Cu aluminum alloy(7 A04)with two-stage stress aging were investigated in 3.5%NaCl solution by polarization curves and electrochemical impedance spectroscopy.The results indicate that with the increase of the stress in 0~300 MPa,the corrosion potential of 7 A04 aluminum alloys is increased and then decreased,while the self-corrosion current density is varied to the contrary.The alloy possesses the best electrochemical corrosion resistance with the aging stress of200 MPa,where the corrosion potential is-0.753 Vand the self-corrosion current density is 5.249×10^(-7)A·cm^(-2).Compared with stress-free and single-stage stress aging,the corrosion potential and AC impedance of 7 A04 aluminum alloy with two-stage stress aging are the higher and the self-corrosion current density is the lower,while its effect on pitting corrosion potential is not obvious.The change of precipitation phase distribution and size in 7 A04 aluminum alloy after stress aging are responsible for improving its electrochemical corrosion resistance.