Effect of Polarization Rate in Potentiokinetic Anodic Polarization of iron in 1N H2SO4

CORROSION ◽  
1970 ◽  
Vol 26 (4) ◽  
pp. 141-150 ◽  
Author(s):  
J. E. REINOEHL ◽  
F. H. BECK ◽  
M. G. FONTANA
Keyword(s):  
Anodic Polarization ◽  
Rate Sensitivity ◽  
Anodic Polarization Curve ◽  
Langmuir Adsorption ◽  
Polarization Rate ◽  
Dilute Sulfuric Acid ◽  
Current Densities ◽  
Physical Variables ◽  
Passive Current ◽  
Logarithmic Variation

Abstract Potentiokinetic data are reported for single crystal and polycrystalline specimens of high purity (56 ppm total impurities) and sulfurized (150 ppm sulfur) iron in 1N H2SO4. Eight polarization rates, ranging from 20 to 1100 mV/min, were investigated. The shape and position of potentiokinetic anodic polarization curves were found to vary appreciably and reproducibly with polarization rate. The observed logarithmic variation of three characteristic passive and transpassive current densities (ix) with polarization rate (η̇) can be expressed by a relation of the form where k and r are constants. The exponent r is given the name “polarization-rate-sensitivity.” At faster polarization rates, current densities tended to be higher and secondary passivity more pronounced. Secondary passivity merged with ordinary passivity at a material-dependent “critical” polarization rate, at which passive current densities were nearly independent of potential. Passive current densities increased with increasing potential at faster polarization rates, corresponding to Langmuir adsorption conditions, and decreased with increasing potential at slower polarization rates, corresponding to Temkin adsorption conditions. The presence and absence of sulfur and of grain boundaries had a negligible quantitative effect on the appearance of the potentiokinetic anodic polarization curve of iron in dilute sulfuric acid solution. However, a small effect of these chemical and physical variables could be expressed by different relations between currents and polarization rate.

Change in Electrochemical Property of 12%Cr Ferritic Steel in 1M-KOH Solution Due to Creep

2010 ◽  
Vol 89-91 ◽  
pp. 1-5 ◽  
Author(s):  
Yousuke Abe ◽  
Shinichi Komazaki ◽  
Toshiki Mitsueda ◽  
Yutaka Kohno
Keyword(s):  
Electrochemical Property ◽  
Thermal Aging ◽  
Material Characterization ◽  
Ferritic Steel ◽  
Anodic Polarization ◽  
Selective Dissolution ◽  
Anodic Polarization Curve ◽  
The Other ◽  
Peak Current ◽  
Current Densities

Electrochemical material characterization method was applied to the creep specimens of 12%Cr ferritic steel to evaluate the changes in precipitates during creep. Experimental results revealed that the peak current densities “Ip1” and “Ip2” appeared at specific potentials during anodic polarization curve measurement in 1M-KOH solution. These peak current densities corresponded to the selective dissolution of several kinds of precipitates, respectively. The Ip2, which reflected the amount of M23C6 and Laves phase, increased more siginificantly with creep than thermal aging. On the other hand, the effect of applied stress was not reflected on the change in Ip1, although it increased with thermal aging and creep as well as the Ip2.

Contribution to the Interpretation of Current Maxima in the Passivity Range of Austenitic Stainless Steels

CORROSION ◽  
1978 ◽  
Vol 34 (11) ◽  
pp. 407-412 ◽  
Author(s):  
A. CIGADA ◽  
G. RE ◽  
D. SINIGAGLIA ◽  
F. BORILE
Keyword(s):  
Current Density ◽  
Stainless Steels ◽  
Anodic Polarization ◽  
Austenitic Stainless Steels ◽  
Sample Surface ◽  
Anodic Polarization Curve ◽  
304 Stainless Steel ◽  
Passive Current Density ◽  
Oxidation Of Hydrogen ◽  
Passive Current

Abstract Passive current density maxima have been observed by various workers during the anodic polarization of different stainless steels in sulfuric acid solutions and have been explained by many theories. This paper describes the precorrosion time and some other pretreatments of the sample surface which change drastically the anodic polarization curve of AISI Type 304 stainless steel in 2N H2SO4, lowering the critical current density and causing two passive maxima. Our results are used in a critical analysis of the conclusions of other authors. The passive current density maxima are attributed to the oxidation of hydrogen formed during precorrosion and absorbed into the alloy and of ions present in the solution and coming from the alloy dissolution.

scholarly journals Electrochemical behavior of AgCu50 in alkaline media in the presence of chlorides and 2-mercaptobenzothiazole

2017 ◽  
Vol 53 (3) ◽  
pp. 349-356 ◽  
Author(s):  
V. Grekulovic ◽  
M. Rajcic-Vujasinovic ◽  
A. Mitovski
Keyword(s):  
Electrochemical Behavior ◽  
Electrode Surface ◽  
Anodic Polarization ◽  
Pure Copper ◽  
Inhibitory Effect ◽  
Open Circuit ◽  
Alkaline Media ◽  
Nacl Solution ◽  
Pure Silver ◽  
Current Densities

Electrochemical behavior of an alloy AgCu50, pure copper, and pure silver, respectively, was investigated by measuring the open circuit potentials using anodic potentiodynamic polarization and potentiostatic method in 0.1 moldm-3 NaOH + 0.02 moldm-3 NaCl solution, without and with adding 2-mercaptobenzothiazole in various concentrations (0.00001 - 0.001 moldm-3). Anodic polarization curves for AgCu50 alloy, showed four current peaks. Potentiostatic curves showed that values of the stationary current densities drop down with the increase of 2-mercaptobenzothiazole concentration in the electrolyte. The electrode surface was analyzed by optical microscopy after the potentiostatic oxidation. Micrographs confirmed that 2-mercaptobenzothiazole has got the inhibitory effect by forming the film of CuMBT and AgMBT which protect the electrode surface from corrosion.

Polarization Studies of Aluminum Alloys In Water at 200 C and 300 C

CORROSION ◽  
1963 ◽  
Vol 19 (4) ◽  
pp. 146t-155t ◽  
Author(s):  
J. H. GREENBLATT ◽  
A. F. McMILLAN
Keyword(s):  
Anodic Polarization ◽  
Cathodic Polarization ◽  
Oxidation Potential ◽  
Electronic Conduction ◽  
Film Resistance ◽  
Applied Current ◽  
Weight Gain Data ◽  
Current Densities ◽  
Polarization Studies ◽  
Impressed Current

Abstract Specimens of commercial 2S aluminum and two special alloys containing iron and nickel were polarized anodically and cathodically at a number of different current densities at 200 C and 300 C. Weight gains were obtained and the potentials relative to the stainless steel autoclave were measured by an interrupter method. The weight gain data indicated that the polarizing current is being carried by electronic conduction. The potential-time curves for anodic polarization indicate differences between 2S aluminum and the alloys in that greater polarization is obtained with the latter. These curves also indicate that the impressed current decreases the film resistance. In all cases the potential reached a plateau value with time and this time was shorter for the alloys. The potential-time curves for cathodic polarization also show plateau values but the rise to a plateau value is in the opposite sense to the applied current. With increasing cathodic polarization the plateau values occur at more negative values of the potential. This latter trend is in the same direction as the applied polarizing current. This apparently is explained in terms of the build-up of the aluminum oxidation potential which acts in a sense opposite to the applied current. Again the time to reach plateau values was shorter for the alloys. Voltage current curves were also obtained on specimens left overnight (approximately 17 hours) at two different anodic polarizing currents. These curves indicated differences between 2S aluminum and the alloys; these differences are discussed in terms of the semi-conducting properties of the oxide film. The observations made on the differences in the properties of the oxide films on the materials examined as revealed by potential and polarization curves are discussed as to their significance in determining corrosion resistance.

INVESTIGATION OF ADSORPTION AND INHIBITIVE EFFECT OF CALIXARENE DERIVATIVE NEWLY SYNTHESIZED TOWARDS C38 STEEL IN MOLAR HCl

2009 ◽  
Vol 16 (03) ◽  
pp. 401-406 ◽  
Author(s):  
R. SOUANE ◽  
M. KADDOURI ◽  
M. BOUKLAH ◽  
N. CHERIAA ◽  
B. HAMMOUTI ◽  
...  
Keyword(s):  
Weight Loss ◽  
Inhibition Efficiency ◽  
Langmuir Adsorption Isotherm ◽  
Enthalpy Of Adsorption ◽  
Langmuir Adsorption ◽  
Corrosion Phenomenon ◽  
Calixarene Derivative ◽  
Current Densities ◽  
C38 Steel ◽  
Mixed Type Inhibitor

The focus of this study is to synthesize a new calixarene derivative namely calix[6]arene (C21) and to test its performance as corrosion inhibitor of C38 steel in molar HCl at 308 K. Polarization and weight loss measurements were used. Weight loss tests show that C21 retards until to stop corrosion phenomenon at 5 × 10-5 M . C21 is an excellent inhibitor and its inhibition efficiency increases with its concentration to reach 100% since 5 × 10-5 M . Polarization curves revealed that C21 affects both cathodic and anodic domains by decreasing current densities and then it may be classified as a mixed type inhibitor. The calixarene tested is adsorbed on the surface according to the Langmuir adsorption isotherm. Free enthalpy of adsorption reveals that C21 acts from chemisorption onto the steel surface.

Effects of Current Density on the Formation of Anodic Oxide Films on AZ91

2006 ◽  
Vol 510-511 ◽  
pp. 166-169
Author(s):  
Seong Jong Kim ◽  
Jeong Il Kim
Keyword(s):  
Corrosion Resistance ◽  
Current Density ◽  
Anodic Polarization ◽  
Oxide Films ◽  
Anodic Oxide ◽  
Anodic Polarization Curve ◽  
Al Alloy ◽  
Anodic Oxide Films ◽  
Active Metal ◽  
Naoh Solution

Magnesium must be surface treated to prevent corrosion, since it is a very active metal electrochemically. On anodizing, a compact film several tens of micrometers thick forms on magnesium, which imparts good corrosion resistance. The Mg-Al alloy (AZ91) was anodized in 1 M NaOH solution. The surface morphology of the anodized films was observed using scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), and electrochemical methods. The effects of current density on the formation of anodic oxide films for a Mg-Al alloy in 1 M NaOH were investigated. In the anodic polarization curve, the reference corrosion potentials were far greater at 4-9 mA/cm2 than at 1 mA/cm2. The film that formed at 1 mA/cm2 was thin, suggesting that parts of the film had been dissolved or destroyed during the anodic polarization test. Corrosion resistance differed owing to concentric differences in current flow. Thick anodic oxide films were formed at higher applied currents.

Effect of Nitrite Ions on Polarization Behavior of Steel Immersed in Simulated Concrete Pore Environments

2013 ◽  
Vol 368-370 ◽  
pp. 919-924
Author(s):  
Zhong Lu Cao ◽  
Makoto Hibino ◽  
Hiroki Goda
Keyword(s):  
Polarization Curve ◽  
Current Density ◽  
Linear Polarization ◽  
Anodic Polarization ◽  
Cathodic Polarization ◽  
Corrosion Current ◽  
Anodic Polarization Curve ◽  
Polarization Curves ◽  
Passive State ◽  
Nitrite Concentration

The influence of nitrite concentration on the linear polarization curves of steel, Tafel slope and Stern-Geary constant B have been investigated in three different pH environments simulating the highly alkaline environment, carbonated environment and neutral environment that really existed on the surface of steel in concrete. The results indicate that when the steel is in passive state, the presence of nitrite has little influence on anodic/cathodic polarization curves and Stern-Geary constant B; but when the steel is corroded, the presence of nitrite not only reduces the current density of anodic polarization curve but also decreases the value of Stern-Geary constant B. If this influence is not considered in practical corrosion measurement, the corrosion current will be overestimated.

Electrochemical Behaviour of Cobalt in NaOH Solutions

1994 ◽  
Vol 59 (11) ◽  
pp. 2383-2389 ◽  
Author(s):  
Sayed S. Abd El Rehim ◽  
Ahmed A. El Basosi ◽  
Salah M. El Zein ◽  
Magda M. Osman
Keyword(s):  
Cyclic Voltammetry ◽  
Passive Film ◽  
Polarization Curve ◽  
Anodic Polarization ◽  
Electrochemical Behaviour ◽  
Anodic Polarization Curve ◽  
Potential Region ◽  
Voltammetric Techniques ◽  
Scan Rate ◽  
Reverse Scan

The electrochemical behaviour of cobalt in 0.001 - 1 M NaOH was investigated by voltammetric techniques coupled with ESCA examination. The anodic polarization curve exhibits a well defined peak which corresponds to the formation of Co(OH)2 or CoO. Further peaks in the transpassive potential region correspond to the electrooxidation of Co(II) species to Co3O4 and CoOOH, respectively. The heights of the anodic peaks increase with the increase of NaOH concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan consistently shows three cathodic peaks which are ascribed to the reduction of CoOOH, Co3O4 and CoO oxides, respectively. ESCA examination confirmed the presence of these oxides in the passive film.

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