超高强度钢无氰镀镉-钛层在循环湿热试验条件下的腐蚀变化规律研究

摘要

Objective To research corrosion behaviors of ultrahigh-strength steel coated with Cd-Ti layer which is plated from non-cyanide bath during thermal-humidity cycling tests. Methods Thermal-humidity cycling test was applied to the sam-ples of ultrahigh-strength steel. Marco and micro images of the samples were taken after each acceleration period. Corrosion behaviors in each acceleration period were researched by electrochemical tests. Results Local corrosion areas distributed on the coating surface of the samples after 384h of thermal-humidity cycling tests; the weight-loss of the samples increased with the increase of test time. However, it increased relatively slowly in the first several testing cycles (≤384 h), while increased faster in the further test (>384 h). The corrosion kinetics equation and curves revealed that the corrosion rate increased dramatically during the later cycling periods. In addition, the impedance magnitude at 0.01 Hz of the sample experiencing thermal-humidity cycling tests over 1536 h was tested to be 102?. Conclusion The coating is corroded in the early cycling periods. It spreads slowly during the middle cycling periods, but get serious in the later cycling periods. The power function fitting equation of the weight loss related to the time is found to be D(t)=0.013t1.2095, while the correlation coefficient is R2=0.9879.%目的 研究超高强度钢表面无氰镀镉-钛层在循环湿热条件下的腐蚀变化规律.方法 对超高强度钢表面无氰镀镉-钛层试样进行循环湿热试验,对各个加速时间段的试样进行宏观照片及微观照片的拍摄,并运用电化学测试分析的方法研究试样在加速试验各时间段的腐蚀变化规律.结果 超高强度钢表面无氰镀镉-钛层经历384 h的循环湿热试验后,镀层首先开始出现腐蚀现象.试样的腐蚀失质量损失随试验时间的延长逐渐增加,且呈现出在试验初期(≤384 h)的增量相对较小,试验中后期(>384 h)的增量相对较大的特征,腐蚀动力学方程和曲线的特征也表明,试样在循环湿热试验后期的腐蚀速率相对较大.经历1536 h循环湿热试验的试样在0.01 Hz处的阻抗模值下降为102?.结论 循环湿热条件下,在加速试验初期,超高强度钢表面无氰镀镉-钛层试样表面镀层开始发生腐蚀,中期腐蚀现象减缓,后期腐蚀现象明显.质量损失数据与试验时间关系的幂函数拟合方程为D(t)=0.013t1.2095,相关指数R2=0.9879.