Potentiostatic anodization

Fig. 1.55 Breakdown potentials of Fe-18Cr-8Ni stainless steel in 0-1 M NaCl plus various concentrations of Soj ions during potentiostatic anodic polarisation (after Leckie and...

Fig. 3.14 Idealised form of a potentiostatic anodic polarisation curve ABCDE for stainless steels as determined in sulphuric acid solution. PQ and P Q arc two cathodic polarisation curves that lead to passivity and corrosion, respectively...

Fig. 10,54 Potentiostatic anodic polarisation curves for mild steel in 10% sulphuric acid. Note the magnitude of the critical current density which is lO -lO A/m this creates a problem in practical anodic protection since very high currents are required to exceed icu. and therefore...

Analysis of experimental data shows that the dependence of the geometrical parameters of oxides on the temperature and concentration of electrolyte is different for galvanostatic and potentio-static conditions (Fig. 35).221 It appears that potentiostatic anodization is limited mainly by processes in the bulk of the oxide and thus is not influenced by temperature (Fig. 35b), whereas the galvanostatic anodization regime involves oxide dissolution processes at the O/S interface depending both on Tel and Cel. 

Spectroscopic ellipsometry is a non-destructive, interface sensitive, in situ technique for interface characterization. Time resolved ellipsometric spectroscopy was used to determine the mechanism of electrochemical deposition of photoresists on copper electrodes under potentiostatic, anodic conditions. Nucleation of photoresist deposition occurs randomly. During the early stages of nucleation the semi-spherical particles are separated by about 100 A. The deposits tend to grow like "pillars" up to 50 A. Further growth of the "pillars" lead to coalescence of the photopolymer deposits. 

Prakasam HE, Varghese OK, Paulose M, Mor GK, Grimes CA (2006) Synthesis and photoelectrochemical properties of nanoporous Iron (III) oxide by potentiostatic anodization. Nanotechnology 17 4285-4291... 

Fig. 5.10 Current-time behavior during 20 V potentiostatic anodization of a Ti foil (99.8 % pure) in a formamide solution containing 5% H2O and identical molar concentrations (0.27M) of fluoride ion bearing compounds with four different cationic species Hydrogen (H ), Ammonium (NH4 ), Tetrabutylammonium ([C4Hg]4N ), and Benzyltrimethylammonium...

Titanium foils were potentiostatically anodized at 25V in an electrolyte of pH 3.5 containing 0.4M ammonium nitrate NH4NO3 and 0.07M HF acid with reference to Fig. 5.26, Sample A was removed after 17 s of anodization, while Sample B was anodized for 240 s. Sample C was anodized for 6 h at 20V in an electrolyte of pH... 

Figure 34 Potentiostatic anodic polarization curves of a Fe 10% Cr 10% Ni alloy in a 1 N H2S04 solution at 25°C as a function of electrode mounting technique. (From Greene et al., France, and Wilde.)...

Fie. 5.23 Potentiostatic anodic polarization curve for copper in deaerated 1 N H2S04 at 25 °C. Redrawn from Ref 20... 

To conclude, the potentiostatic anodization of metallic tungsten in an appropriate electrolytic composition provides a simple wet electrochemical tool [80] to produce highly efficient WO3 photoanodes, which, combining spectral sensitivity, highly electrochemically active surface, and improved charge transfer kinetics outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by sol gel methods and are, at the very minimum, comparable to substrates produced with vacuum technologies (i.e., RF sputtering) recently reported in the literature. 

Potentiodynamic and potentiostatic anodic polarization curves obtained at the same sweep rate are identical. They identify corrosion properties of passivating metals and alloys and are very useful in predicting the corrosion properties of materials. Figure 4.5 shows potentiostatic polarization curve of an active-passive metal with more than one passivation potential. 

Fig. 4.6 Hematite morphologies accessible by potentiostatic anodization The left (top and bottom) shows SEM images of structures from the work of Prakasam et al. [87] and the right (top and bottom) shows images of tubes from Rangaraju et al. [88]. SEM images used with permission from [87] and [88]...

Figure 6.1. Potentiostatic anodic polarization curve for iron in N H2SO4.

Figure 6.14. Values of critical and passive current densities obtained from potentiostatic anodic polarization curves for copper-nickel alloys in N H2SO4, 25°C [42]. (Reproduced with permission. Copyright 1961, The Electrochemical Society.)...

In a comparative study of potentiostatic anodic polarization methods, Greene and Leonard found that the anodic polarization characteristics were strongly controlled by the experimental procedure employed.They concluded that while potential sweep techniques yielded the most reproducible results, they were not necessarily the most accurate and that measurements should be conducted as slowly as possible, even though only qualitative data are required. 

Just as in the limiting case of ohmic control, the depth of the corrosion pit increases with the square root of the time. However, the proportionality constant here differs, it includes the saturation concentration rather than the potential and the diffusion coefficient rather than the electrolyte conductivity. Figure 7.64 shows experimental results for potentiostatic anodic dissolution of nickel in chloride solution. The geometry of the electrochemical cell corresponds to the one-dimensional pit model represented in Figure 7.62. The results show that, after a certain time, the current density decreases according to the square root of the polarization time, independent of potential. Mass-transport controlled growth of corrosion pits is favored by a highly electrolyte conductivity and weakly soluble dissolution products. 

---