碳钢钝化膜在碳酸盐溶液中的阴极还原机理

The Cathodic Reduction Mechanism of Passive Film on Mild Steel in Carbonate Solution

本文采用动电位和恒电流技术研究了pH8.31-11.37的碳酸盐缓冲溶液中,低碳钢钝化膜的阴极还原机理。认为钝化膜的还原与溶液pH值密切相关,当8.31≤pH≤9.80时,Fe_2O_3还原为Fe和Fe0H^+;当9.80<pH≤11.37时,Fe_2O_3还原为Fe_3O_4和Fe(CO_3)_2^(2-)。两反应的控制步骤均为FeOH^(2+)+2e→Fe(OH)_(ads)。

The cathodic reduction of passive film on mild steel has been investigated by the potentiodynamic and galvanostatic techniques in carbonate-bicarbonate buffer solutions at various pH values. The reduction strongly depends on the pH value of the solutions. At 8.31≤pH≤9.80, ferric oxide was simultaneously reduced to Fe and FeOH^+ ion; while at 9.80≤pH≤11.37, ferric oxide was reduced to magnetite and Fe(CO_3)_2^(2-) ion. Both of these reaction consisted of a number of steps, and the rate-determining step was the charge transfer reaction from FeOH^(2+) to (FeOH)_(ads).