摘要
采用交变电场脉冲钝化技术表面改性Fe24Mn4Al5Cr反铁磁定膨张合金.在1.0 mol/L Na_2SO_4溶液中通过脉冲钝化生长钝化膜,再在1.0 mol/L Na_2SO_4+0.5 mol/L H_2SO_4溶液中测定电位衰减曲线,以优化脉冲钝化工艺参数.利用AES和XPS分析优化工艺条件下生长的脉冲钝化膜化学组成、键合状态及其深度分布;利用阳极极化曲线和电化学阻抗谱测试脉冲钝化膜耐腐蚀性能,并与直流620 mV连续钝化15 min生长钝化膜相比较.研究发现,脉冲钝化膜中元素Al和Cr富集,元素Mn贫化,具有保护性的Al_2O_3和Cr_2O_3氧化物阻碍层增厚.脉冲钝化膜的阳极极化曲线呈自钝化,自腐蚀电位E_(corr)由连续钝化膜的-360 mV增至-100 mV,维钝电流密度i_p由2.6μA/cm^2降至0.7μA/cm^2,阳极极化性能与AISI 304不锈钢相当.脉冲钝化膜的EIS与连续钝化膜相比,其容抗弧直径及|Z|值增加,相位角平台变宽,利用等效电路R_s-(R_p∥CPE)拟合的脉冲钝化膜电阻R_p由连续钝化膜的14.8 kΩ·cm^2增至54.0 kΩ·cm^2,计算的有效电容C_B则由14.0μF/cm^2降至10.2μF/cm^2.Fe24Mn4Al5Cr反铁磁定膨胀合金脉冲钝化膜的绝缘性提高,耐蚀性改善.
An antiferromagnetic Fe24Mn4A15Cr covar alloy has been impulse-passivated by an alternating current （AC） voltage overlapping a direct current （DC） voltage, in order to improve its corrosion resistance due to the poor corrosion property of austenite matrix with a high Mn content, a low Cr and/or A1 content. The impulse-passivated films were obtained in 1.0 mol/L Na2SO4 solution at an AC voltage with modulation amplitude of 180--480 mV during alternating period of 200--- 400 ms for modification time of 5--15 min, and simultaneously at a DC voltage of 620 mV. The impulse-passivation parameters in 1.0 mol/L Na2SO4 ＋ 0.5 mol/L H2SO4 solution were optimized as amplitude of 380 mV, period of 300 ms, and time of 10 min, by using the potential decline curves. The impulse-passivated films on the covar alloy under the optimum parameters were characterized by Auger electron spectroscopy and X-ray photoelectron spectroscopy （AES/XPS）, and evaluated by anodic polarization and electrochemical impedance spectroscopy （EIS）, respectively, and compared with those of the constant-passivated films at DC voltage of 620 mV for modification time of 15 min. In the impulse-passivated films on the covar alloy, an enrichment of elements A1 and Cr, a lack of Mn in a thick barrier film composed of oxides A1203 and Cr203. The anodic polarization curves of the impulse-passivated films have a self-passivation with the higher corrosion potential of -100 mV and lower passive current density of 0.7 μA/cm2, than those of -360 mV and 2.6μA/cm2 for the constant passivated films. These electrochemical polarization behaviors were similar to those of the AISI 304 austenitic stainless steel. The EIS of the impulse-passivated films has larger diameter of capacitive arc, higher impedance modulus IZI, and wider phase degree range, relative to the constant-passivated films. Correspondently, the impulse-passivated film resistant Rp increased to 54.0 kΩ.cm2 from 14.8 kΩ.cm2 and effective capacitance decreased to 10.2 μF/cm2 from 14.0 μF/cm2, using an equivalent electric circuit of Rs-（Rp//CPE）. The high insulation of the impulse-passivated films on the covar alloy led to an improved corrosion resistance of the cover alloy. The impulse-passivated antiferromagnetic Fe24Mn4A15Cr covar alloy exhibits an application potential in wide industrial field.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第11期1357-1364,共8页
Acta Metallurgica Sinica
基金
国家自然科学基金资助项目50725519~~
关键词
Fe-Mn—Al合金
脉冲钝化
钝化膜
电位衰减
阳极极化
电化学交流阻抗
Fe-Mn-Al alloy, impulse-passivation, passive film, potential decline, anodic polarization, electrochemical impedance spectroscopy
