Potential vs. time

Legault, Mori and Leckie have used open-circuit potential vs. time measurements and cathodic reduction of rust patinas for the rapid laboratory evaluation of the performance of low-alloy weathering steels. The steel specimens are first exposed for 48 h to the vapour of an 0-(X)l mol dm sodium bisulphite solution maintained at 54°C (humid SOj-containing atmosphere) to stimulate corrosion under atmospheric conditions. They are then subjected to two types of test (tt) open-circuit potential-time tests for periods up to 3 000 s in either distilled water or 0 -1 mol dm Na2S04 and... 

Calculation of Model. Examination of Figs. 1 and 2 suggest the initial choice of p=l for the autoregression part, and the use of 1st differences, i.e. an ARIMA (1 1 0) model. The potential vs. time data was fit using this model. 

Figure 3 is a plot of the observed and forecast values of potential vs. time. In general the fit is reasonable through most of the range. The 95% confidence limits of the forecast values are shown. 

Figure 1. Open circuit potential vs. time in sterile medium and in medium with bacteria (a) platinum, (b) 304L stainless steel. (Reprinted from Ref 1 with permission from NACE International.)...

Figure 14.3 Schematic illustrations of expected current density vs. time, true electrode potential vs. time, and coverage of the surfactant vs. time curves.

Figure 3. Long-term corrosion measurement of an electrolytic Sn-Zn alloy containing 26% Zn (by weight) in a 3% NaCI solution, pH = 4.000, with argon bubbling through the solution. Upper diagram corrosion potential vs. time lower diagram CMT and EC measurements vs. time. After 80-100 min, the ratio CMT/BC is close to 4. (Reprinted from Ref. 2, with kind permission from Elsevier Science Ltd., Kidlington, Oxfmd, UK.)...

Figure 5. Potential vs time for coated specimens in 3% NaCl. Key , bitumen A, Zn rich + bitumen 0> polyurethane, one coat (unpigmented) V, polyurethane, two coats (unpigmented) 0, polyurethane, one coat (pigmented) and X, polyurethane, two coats (pigmented).

Fig. 18. A chronopotentiometric experiment, (a) Current step (b) potential vs. time response.

Figure 2. Potential vs. time responses of Na+ ISFETs in standard blood serum (a) PVC, (b) Uruslii, (c) KP-13.

Figure 26 Corrosion potential vs. time for Type 410 stainless steel in 0.5 M NaCl + 0.01 M H202. The breakdown potential is indicated by the dotted line. Once this potential is exceeded, the potential falls as stable, localized corrosion begins to propagate.

Figure 27 Schematic (a) Evans diagram and (b) corrosion potential vs. time behavior for localized corrosion stabilization. Line a on the Evans diagram represents the electrochemical behavior of the material before localized corrosion initiates, while line b represents the electrochemical behavior of the material in the localized corrosion site. Due to the low Tafel slope of the active site, the corrosion potential of the passive surface/local-ized corrosion site falls. If repassivation occurs, the anodic behavior reverts back to line a, and the corrosion potential increases again (line c). If repassivation does not occur, the corrosion potential will remain low (line d).

Cyclic chronopotentometry — A controlled current technique where the applied - current step is reversed at every transition time between cathodic and anodic to produce a series of steps in the potential vs. time plot - chronopotentiogram. The progression of transition times is characteristic of the mechanism of the electrode reaction. For example, a simple uncomplicated electron transfer reaction with both products soluble and stable shows relative -> transition times in the series 1 0.333 0.588 0.355 0.546 0.366... independent of the electrochemical reversibility of the electrode reaction. 

Figure 9. The discharge behavior of (potential vs time) for LiCo02 (current applied in mA/cm ).

Fig. 2. Typical potential ( ) vs time recording obtained for assay of urease with an ammonia gas sensing electrode. Curve shown is for addition of IS /tl of 6 Af urea to 1 ml of 0.4 nM urease in 0.1 M Tris-HCl-1 mM EDTA, pH 7.5.

Figure 6. The potential vs time plot for cyclic voltammetry. For linear sweep voltammetry only the first linear ramp is used.

Figure 23-24 (a) Potential vs. time waveform and (b) cyclic voltammo-gram for a solution that is 6.0 mM in K3pe(CN)6 and 1.0 M in KNO3. (Used with permission from P. T. Kissinger and W. H. Heineman, J. Chem. Educ., 1983, 60, 702. Copyright 1983 Division of Chemical Education, Inc.)... 

Electrochemical corrosion techniques are essential to predict service life in chemical and construction industries. The following direct current (dc) electrochemical methods are used in corrosion engineering practice linear polarization technique, Tafel extrapolation, and open circuit potential vs. time measurements. The alternating current (ac) technique is electrochemical impedance spectroscopy (EIS). This technique uses alternating current to measure frequency-dependent processes in corrosion and estimates the change of polarization resistance as a function of time. 

Figure 9.12 Corrosion potential vs. time in aerated isotonic saline. (Buchanan and Lee, 1990.)...

FIGURE 4.3.9. Potential vs time profile following current interruption [44]. (Reproduced by permission of The Electrochemical Society, Inc.)... 

Fig. 40. Potential vs. time profile used in rapid SW technique with a time delay. Characteristic parameters t (delay time) = 5 s, dEgt = 5 mV, dEsw = 25 mV, tp = 20 ms. Points 1 and 2 sampling times for forward and backward reactions. Adapted according to [96].

The applied potential vs. time waveforms corresponding to this table are shown in Figure 4.4. 

Figure 4.4 The potential vs. time waveforms for PAD and IPAD. The times and potentials for the waveforms are listed in Table 4.7.

R dox Capacitor, Fig. 2 Voltage or potential vs. time curves during galvanostatic cycles of the EC cell utilizing... 

The electrochemical techniques can be divided into two major groups static (i = 0) and dynamic (i + 0) (6). Potentiometry is a static method, and it measures the rest potential vs. time the most common applications in potentiometry are the use of ion-selective electrodes and pH meters. The dynamic methods comprise mostly all the other electrochemical techniques (3). Table 1.1 lists the most commonly used methods among this group. 

Fig. 2. Plots of the electrode potentials and the potential signals for temperature difference against time for the 0.2mol.dm-3 [Fe(CN)6] / system at various electric currents, (A) the electrode potentials vs. time, (B) the potential signals for temperature difference vs. time the curves from No.l to No.8 correspond to currents 1.0, 2.0, 2.5,3.5,4.0, 5.0, 6.0 and 7.0 mA, respectively...

Fig. 4. Open circuit potential vs. time curves for SS (a) and SSt.t.(b), as well as for the systems Ce02-Ce203/SS (a) and Ce02-Ce203/SSi.t..(b), containing different concentrations of Ce, obtained in 0.1 N H2SO4.

Figure 2.3 CV potential vs. time perturbation wave-form...

Figure 6. Cell potential vs. time for a LiFePOVgraphite cell containing a 2,5-ditertbutyl-l,4-dimethoxybenzene shuttle additive. The electrolyte salt was 0.7 M LiBOB. The x axis for (a) covers the time period of 0-50 h, (b) 1,000-1,050 h, (c) 2,000-2,050 h, (d) 3,500-3,550 hours.

Figure 10. (a) Potential vs. time for a LiFeP04/Li4Ti50i2 coin cell containing 0.1 M MPT in 0.5 M LiPF electrolyte solution chargedand discharged at a nominal C/2 rate. Selected cycles are shown, (b) Positive electrode specific capacity vs. cycle number for the same cell. 

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