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采用SEM,TEM,动电位极化和浸泡实验研究了机械冷加工变形对汽车散热器高Mn(0.22%,质量分数,下同)和低Mn(0.08%)铝合金管在0.6 mol/L NaCl(pH=6)和SWAAT(ASTM G85,pH=3)溶液中的腐蚀行为的影响.电化学极化测试表明,无形变时高Mn铝合金直管的点蚀电位最高;但冷加工能降低高Mn铝合金弯曲表面的点蚀电位,而对低Mn铝合金的点蚀电位没有明显影响.TEM观察发现,冷加工后高Mn铝合金中有大量纳米尺度的富Mn析出相,在低Mn铝合金中却没有观察到这种析出相,阴极极化测试表明,富Mn相能显著促进阴极反应,富Mn相相对Al基体为阴极相,因而是点蚀萌生的部位.添加Mn尽管有利于提高铝合金的耐蚀性,但机械冷加工会弱化这一效应.
SEM, TEM, potentiodynamic polarization and immersion experiments were carried out to investigate the effect of mechanical cold deformation on the mechanical properties of automobile radiator with high Mn (0.22%, mass fraction) and low Mn (0.08%) aluminum alloy tube in 0.6 mol / L NaCl pH = 6) and SWAAT (ASTM G85, pH = 3) .The electrochemical polarization tests showed that the pitting potential of high Mn aluminum alloy straight tube was the highest without deformation, but the cold working could reduce the high Mn The pitting potential of the curved surface of the aluminum alloy has no significant effect on the pitting potential of the low-Mn aluminum alloy. According to the TEM observation, a large number of nano-scale Mn-rich precipitates are formed in the high-Mn aluminum alloy after cold working, But did not observe this precipitation phase, cathodic polarization test showed that Mn-rich phase can significantly promote the cathode reaction, Mn-rich phase relative to the Al matrix as the cathode phase, which is the site of pitting initiation.Although adding Mn is beneficial to improve the aluminum alloy Of the corrosion resistance, but mechanical cold-working will weaken this effect.