Competitive effects of metal dissolution and passivation modulated by surface structure: An AFM and EBSD study of the corrosion of alloy 22
Competitive effects of metal dissolution and passivation modulated by surface structure: An AFM and EBSD study of the corrosion of alloy 22
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DOI：
10.1016/j.susc.2006.04.002
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发表时间：
2006-06-15
期刊：
影响因子：
1.9
通讯作者：
Orme, C. A.
中科院分区：
文献类型：
--
作者：
Gray, J. J.;El Dasher, B. S.;Orme, C. A.
使用电子背散射衍射（EBSD）和原子力显微镜（AFM）将多晶合金22在浸入1和3摩尔（M）盐酸中之后的晶粒取向与腐蚀速率相关联。对于每个酸浓度，相对腐蚀速率的同时，其特征在于约50个独特的晶粒取向。结果表明，在两种酸浓度下，腐蚀速率各向异性明显不同。在非常侵蚀性的酸性环境（3 M HQ，其中电化学阻抗谱和光谱椭圆偏振法数据证明合金22的钝化氧化物膜完全溶解，对于给定的晶粒取向，合金溶解速率与表面原子的平均配位数成反比，其中高度相关的表面溶解最慢。因此，类似于简单的金属系统，腐蚀速率与表面平面法向晶体学取向成比例，为{111} < {100} < {110}。不那么直观的是，在较温和的腐蚀环境（1 M HCl）中，合金的钝化膜仍然完好无损，溶解不会与表面原子密度成反比。相反，腐蚀速率与晶体取向成比例，为{111} < {110}< {100}。这归因于最易受腐蚀（最不协调）的刻面也最能够形成保护性氧化物的事实，使得溶解各向异性是金属溶解和氧化物生长之间的微妙平衡的结果。(c)2006 Elsevier B. V.保留所有权利。
Electron backscatter diffraction (EBSD) and atomic force microscopy (AFM) are used to correlate crystallographic grain orientation with corrosion rates of polycrystalline alloy 22 following immersion in 1 and 3 molar (M) hydrochloric acid. For each acid concentration, relative corrosion rates are simultaneously characterized for approximately 50 unique grain orientations. The results demonstrate that the corrosion rate anisotropies are markedly different in the two acid concentrations. In very aggressive acidic environments (3M HQ, where electrochemical impedance spectroscopy and spectroscopic ellipsometry data demonstrate that the passive oxide film of alloy 22 is completely dissolved, alloy dissolution rates scale inversely with the average coordination number of surface atoms for a given grain orientation, where highly correlated surfaces dissolve the slowest. Thus, similar to simple metallic systems, the corrosion rates scale with the surface plane-normal crystallographic orientations as {111} < {100} < {110}. Less intuitively, in milder corrosive environments (1M HCl), where the passive film of the alloy is still intact, the dissolution does not scale inversely with surface atomic density. Rather, corrosion rates scale with crystallographic orientations as {111} < {110) < {100}. This is attributed to the fact that facets most susceptible to corrosion (least coordinated) are also the most able to form protective oxides, so that the dissolution anisotropy is a result of the delicate balance between metal dissolution and oxide growth. (c) 2006 Elsevier B.V. All rights reserved.