等通道转角挤压Zn-22Al合金在NaCl水溶液中的腐蚀行为

研究了等通道转角挤压 (ECAP) 工艺处理对Zn-22Al合金耐腐蚀性能的影响，考察了显微组织演变对Zn-22Al合金在3.5% (质量分数) NaCl溶液中的失重及电化学腐蚀行为的影响。结果表明：相比铸态Zn-22Al合金，经过ECAP处理后的试样组织明显细化，晶粒尺寸均匀。晶粒细化导致晶界大量增加及应力增大，试样表面缺陷增多，富铝相被优先腐蚀后，导致被富铝相包围的富锌相脱落，腐蚀速率加快，腐蚀失重随着挤压道次的增加而增加。电化学测试结果表明，随着挤压道次的增加，Zn-22Al合金腐蚀电流密度逐渐增加，腐蚀电位逐渐下降，合金的耐腐蚀性能随挤压道次的增加而逐渐降低。

Corrosion Behavior of Equal-channel-angular-pressedZn-22Al Alloys in NaCl Aqueous Solution

The influence of equal-channel-angular-press (ECAP) process on the corrosion behavior of Zn-22Al alloy in 3.5% (mass fraction) NaCl solution has been studied by means of immersion test and electrochemical measurement. The results showed that the microstructure of the alloy was refined by ECAP process with much uniform grain size distribution rather than that of the as-cast one. Al-rich phase of the ECAP alloy was preferentially corroded in the corrosion process, leading to the isolation and then falling off from the alloy of the Zn-rich phase surrounded by Al-rich phase, therewith the corrosion rate was enhanced. This phenomenon might be ascribed to the increase of grain boundaries, stress and defects of the alloy induced by ECAP process. In general, with the increasing pass of ECAP, the weight loss of the alloy in immersion test increased, while the corrosion current density increased and the corrosion potential decreased, therewith the corrosion resistance was degraded with the increasing ECAP pass for the alloy.