Potentiodynamic polarisation

Cyclic voltammetry (adsorption, monolayers) Potentiodynamic polarisation (passivation, activation) Cathodic reduction (thickness) Frequency response analysis (electrical properties, heterogeneity) Chronopotentiometry (kinetics)... 

Fig. 3.56 Potentiodynamic polarisation curves for high-chromium white irons in nitrogen-saturated solution containing 800mg/l Cl , pH 3.5. 25°C...

Fig. 8.5 Potentiodynamic polarisation curves and the expected domains of electrochemical...

The time factor in stepwise potentiostatic or potentiodynamic polarisation experiments is very important, because large differences can be caused by changes in the scanning rate. Since the steady state depends on the particular system and conditions of exposure, no set rule exists for the magnitude or frequency of potential changes. Chatfield etal. have studied the Ni/H2S04 system and have shown how becomes more passive with increase in sweep rate. 

Potentiodynamic polarisation The characteristics of passive/active conditions for metals can be readily defined using this technique ". Details for laboratory application can be found in ASTM Standard G5 (latest revision). Application in plant is easily performed as portable equipment (potentiostat) is available from several manufacturers, with some models incorporating built-in computer facilities. 

To counteract the high corrosion rate of Mg alloy implants electrochemically deposited coatings of fluorine-doped hydroxyapatite (FHAp) and brushite (DCPD) were developed by Bakhsheshi-Rad et al. (2014). As shown in Table 5.2 potentiodynamic polarisation measurements of uncoated and coated Mg-Ca alloys subjected to electrochemical corrosion in Kokubo s SBF (Table 7.8) confirmed the corrosion-resistant nature of the coatings. The anodic polarisation curve of the uncoated specimen shows a breakdown immediately after the... 

Matthews, 2000). A phosphate salt solution and an aqueous suspension of HAp powder were used as an electrolyte for PEO and EPD, respectively. The corrosion resistance was assessed by potentiodynamic polarisation tests in a buffered physiological solution (see also Kwok et al., 2009). The results of this study indicated that a hybrid combination of PEO and EPD produces an osseoconductive phase-pure ITAp layer and an anticorrosive titania interlayer that promise to provide good mechanical and biochemical stability in the highly corrosive environment of the human body. Other studies involving titania bond coats include Albayrak and Altintas, 2010 Paluszkiewicz, Dlugon andKwiatek, 2012 Rath etal., 2012 and Jain etal. (2013). 

Figure 7.56 Determination of the anodic (pa) and cathodic (Pc) Tafel slopes from the potential versus current density plot obtained by potentiodynamic polarisation testing.

Figure 7.58 Potentiodynamic polarisation curves of uncoated and coated bioinert Ti alloy (a) and biodegradable Mg alloy (b). For explanation see text.

A1 PANI Potentiostatic polarisation Potentiodynamic polarisation in 0.1 M tosylic acid PANI/Al substrate interactions give rise to oxidation of the aluminium and reduction of the polymer. PANI deposits appeared to offer only a slight increase in the corrosion resistance of aluminium. [15]... 

Cu PNEA Cyclic voltammetry Potentiodynamic polarisation and ElSinO.l MH,SO, 2 4 The corrosion rate of Cu is reduced by PNEA coatings electrodeposited at the lowest upper potential limit for shorter periods, by PNEA coatings electrode-posited at the highest upper potential limit for longer periods. [17]... 

Cu POEA Cyclic voltammetry Potentiodynamic polarisation and EIS in 3% NaCl The corrosion rate of POEA-coated Cu is about 70 times lower than that of uncoated Cu. [18]... 

Steel PoPD Cyclic voltammetry Potentiodynamic polarisation and EIS in 0.5 M NaCl PoPD acts as a better protective layer than PANl on steel against pitting corrosion. ... 

Steel Galvanostatic deposition Potentiodynamic polarisation, monitoring OCP, and EIS in 3.5% NaCl PPy coating has worse anticorrosion properties than PPy+ZnO coating with 10 wt.% of ZnO relative to PPy. [31]... 

Steel Cyclic voltammetry Tafel polarisation in 0.1 MHCl EIS in 0.5 M NaCl, 0.1 MHCl Potentiodynamic polarisation in 0.5 M H SO All corrosion tests show the best performance of PPy single coating with respect to the single PANl coating, and PANI/PPy and PPy/PANl bi-layer coatings. [29]... 

PANI Benzoate Steel Galvanostatic deposition Potentiodynamic polarisation in 3% NaCl, outdoors, and in atmosphere Benzoate-doped PANI coatings could protect steel in the three different environments for a limited period of time. [74]... 

POT CdO Steel Cyclic voltam- metry Potentiodynamic polarisation in 3% NaCl The incorporation of CdO ncuiopcffticles improves the corrosion protection of POT coating. [52]... 

PANI SiO A1 Dipping Potentiodynamic polarisation in 0.5 M NaCl The corrosion protection ability of PANi-i-SiO coating decreases when the TEOS (precursor of SiO ) increases. [50]... 

Potentiodynamic polarisation of the panels with 0.5 mV/s scan rate in electrolytic solution was carried out as per standard [17] and voltage was used in the range of —250 mV—1000 mV with respect to SCE. 

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