It is proved experimentally that the relaxation and complex electrochemical oscillations could be induced by inserting external resistors in the electrochemical systems in which bistability could be found.FeH2SO4 system,in which the Fe electrode exhibited bistability within the potential range of 0.309 V～0.406V(vs.SCE),was chosen in our experiments.When the applied potential was 0.340 V and no external resistor was inserted,no oscillations could be observed.While the applied potential was kept at 0.340 V and an appropriate external resistor was connected in series to the electrochemical system,relaxation or complex oscillations appeared.Upon the external resistance increased,the amplitude of the oscillations decreased gradually.The inducement of electrochemical oscillations is helpful to understand the mechanism of the metals dissolution and passive,and to control the dynamic behavior of some electrochemical systems.
Corrosion potential measurement,electrochemical impedance spectroscopy(EIS) and scanning electronic microscopy(SEM) were employed to study the inhibition of hexamethylenetetramine(HA) on corrosion of AZ31 magnesium alloy in simulated coolant.HA exhibits good inhibition after the inducement period through strong adsorption on AZ31 magnesium alloy surface.The addition of HA improves the corrosion resistance of the alloy and affects the corrosion potential little.HA is a mixed-type inhibitor that inhibits both anodic and cathodic reactions of AZ31 magnesium alloy in simulated coolant.
