Galvanic corrosion behaviors of Q235-304L couple in Na₂S solution

Galvanic corrosion behaviors of Q235-304L couple with various cathode/ anode area ratios in three different concentrations of Na₂S solutions were studied by the potentiodynamic polarization curves, galvanic method and immersion test. Surface morphologies of the samples were also analyzed by SEM after rust cleaning. The results showed that:both the cathodic and anodic processes of 304L were controlled by the electrochemical step, while the anodic process of Q235 exhibited an apparent characteristics of activation - diffusion mixed control; a cathodic process as well as an anodic process took place on the surface of Q235 after coupled and the dissolution current of Q235 was much more above the galvanic current got by galvanic corrosion method; as the area ratio increases, the galvanic effect increases; and with the elevation of the concentration of S^2-, the corrosion rate of Q235 decreased, so did the galvanic effect.