H_2S对硫酸溶液中铁腐蚀作用的CNDO/2研究

CNDO/2 Study on the Action of Hydrogen Sulfide in the Corrosion of Iron in Sulfuric Acid Solution

动电位扫描得出工业纯铁在含H_2S的H_2SO_4溶液中腐蚀的电化学行为.应用CNDO/2法确定了阴、阳极电位下H_2S,HS^-在金属Fe晶面上的稳定吸附取向与最佳吸附间距,通过对吸附物总能量、结合能、净电荷分布的计算,得出H_2S体系阴、阳极反应被加速的微观机制.阳极电位下,大量HS^-为S原子的平行吸附方式,HS^-负电荷大部分向Fe转移,促进铁的溶解.阴极电位下,少量H_2S则为H原子的平行吸附方式,Fe表面负电荷向H_2S分子中与Fe作用的H转移,促进析氢.在CNDO/2法计算的基础上,圆满地解释了实验结果.

The electrochemical behavior of iron in H2S - containing H2SO4 solutions has been studied by polarization curve method. The stable adsorption orientation and optimal adsorption distance of H2S and HS- on the crystal plane of iron at cathodic and anodic potential were determined by CNDO/2 method. By calculating the total energy, binding energy and net charge distribution of the absorptives, the adsorption behavior of H2S and HS- on the crystal plane of iron and the bonding state between iron and H2S/HS- at cathodic and anodic potential have been investigated. The following were inferred from the above results. At anodic potential, the adsorption of large amounts of HS- on the crystal plane of iron in parallel direction through sulfur atom, which transferred the most of negative charge from HS-, promoted the dissolution of iron. While at cathodic potential, the adsorption of small amounts of H2S on the crystal plane of iron in parallel direction through hydrogen atom and the negative charge transfer from iron to hydrogen atom in H2S interacting with iron promoted the evolution of hydrogen. The experimental results are satisfactorily explained with the above theoretical calculation.