Oscillatory Phenomena as a Probe to Study Pitting Corrosion of Iron in Halide-Containing Sulfuric Acid Solutions

Corrosion Potential Oscillation of Iron Electrodes in Nitric Acid

“…S1), a current oscillation was observed in the potential region of N-NDR (i.e., at potentials between 0.45 and 0.5 V) under potential-controlled conditions. 18 A hysteresis loop was observed under current-controlled conditions, indicating that the current oscillation is an N-NDR oscillator.…”

“…3) increased the local pH near the electrode surface because H + ions migrated away from the electrode surface to maintain electroneutrality. 18,24,46 Thus, to precisely simulate the behavior of the corrosion potential oscillation, the local pH (i.e., H + concentration at the electrode surface) should be considered. However, for simplicity, this simulation employed the surface concentration of a reactive species instead of the surface concentrations of Fe 2+ and H + and used a simple model described by ordinary differential equations (ODEs).…”

“…For example, various metals exhibit current or potential oscillations when dissolved under appropriate conditions. [17][18][19][20][21][22][23][24][25][26][27][28] In general, an N-shaped negative differential resistance (N-NDR) plays a crucial role in the appearance of oscillations because it results in oscillatory instability. 15,16,29,30 Most oscillations can be classified as N-NDR or "hidden" N-NDR (HN-NDR) oscillators.…”

“…Therefore, bistability is absent, and consequently, hysteresis loops are not observed in the I-U curves obtained under current-controlled conditions. For example, in an iron-sulfuric acid system, the anodic dissolution of iron shows a current oscillation caused by an N-NDR characteristic due to surface passivation [17][18][19][20][21][22][23][24][25] and the oscillation is a typical example of an N-NDR oscillator. The iron-nitric acid system also shows current oscillations caused by N-NDR characteristics.…”

Assessment of Steel Reinforcement Corrosion State by Parameters of Potentiodynamic Diagrams

“…It is referred as an area corresponding to active region (up to critical primary passivation potential E pp [6] and critical current density i crit ). After transition region (BC), characterized by the decrease of current density by increasing the potential, the impeded access of media to reinforcement will be reflected in a nearly constant magnitude of current density (i p ) at increasing potential, called as the passive region (CD) [7]. The most negative potential in this state is called the Flade potential E F [5,6].…”