Some Errors in Linear Polarization Measurements and Their Correction

CORROSION ◽  
1974 ◽  
Vol 30 (3) ◽  
pp. 92-96 ◽  
Author(s):  
FLORIAN MANSFELD
Keyword(s):  
Polarization Curve ◽  
Linear Polarization ◽  
Corrosion Potential ◽  
Corrosion Current ◽  
Potential Curve ◽  
Polarization Measurements ◽  
Tafel Slopes ◽  
The Relationship ◽  
Current Potential

Abstract The errors due to the use of the approximation Icorr′ = B′ΔI, where B′ depends on anodic and cathodic Tafel slopes, in commercial corrosion current meters is shown to be due to the nonlinearity of the current-potential curve in the vicinity of the corrosion potential. These errors are calculated for various combinations of Tafel slopes. It is proposed to use the relationship Icorr = κΔI, where κ depends on Tafel slopes, sign, and magnitude of polarization. The values of κ are tabulated for various combinations of Tafel slopes and polarization of +10 and −10 mV. The proposed procedure leads to correct values of corrosion currents independent of the degree of nonlinearity of the polarization curve.

Evaluation of Corrosion Rates from Polarization Measurements

CORROSION ◽  
1975 ◽  
Vol 31 (5) ◽  
pp. 173-177 ◽  
Author(s):  
RODNEY L. LeROY
Keyword(s):  
Polarization Curve ◽  
Corrosion Potential ◽  
Corrosion Current ◽  
Powerful Method ◽  
Polarization Data ◽  
Polarization Measurements ◽  
Corrosion Rates ◽  
Tafel Slopes ◽  
Tafel Constants

Abstract Polarization measurements within 5 to 20 mV of the corrosion potential offer a powerful method for determining corrosion rates. In this paper, known methods for evaluating the corrosion current from polarization data are critically examined. It is noted that calculated currents are generally in error when the anodic and cathodic Tafel slopes are precisely known, due to non-linearity of the polarization curve. A new result is derived, which allows the corrosion current to be calculated without error if the Tafel slopes are known. Diagrams are presented which show the sensitivity of calculated corrosion rates to errors in estimation of the Tafel constants.

scholarly journals Insights from corrosion current measurements on corrosion mechanisms in reinforced concrete and on the evaluation of other corrosion data

2019 ◽  
Vol 289 ◽  
pp. 03008 ◽  
Author(s):  
Ulrich Schneck
Keyword(s):  
Reinforced Concrete ◽  
Linear Polarization ◽  
Polarization Resistance ◽  
Corrosion Behaviour ◽  
Corrosion Current ◽  
Material Loss ◽  
Polarization Measurements ◽  
Tafel Polarization ◽  
Macro Cell ◽  
Current Densities

During the past years Tafel polarization measurements have been implemented into the scope of measurements of CITec corrosion diagnosis projects. This has created a vast database of different and corresponding corrosion parameters, such as chloride and water content in the rebar vicinity, open circuit potential, electrolyte resistance, polarization resistance (from galvanostatic pulse and linear polarization) and corrosion current from Tafel polarization measurements. Although general limitations in using these methods on macro cell systems such as reinforced concrete are known, the comparative assessment of these data has led to a better understanding of the corrosion behaviour and of specific circumstances of the structures which deviated partly from usual expectations. For instance, a low polarization resistance at high chloride content will not result necessarily in a high corrosion current, if the reinforcement in the wider vicinity of the test location is similar active, and cathodic rebar areas are either very distant or retarded by very wet concrete. So the extended range of corrosion testing gives a more precise evaluation of the corrosion situation and permits a tailored repair and maintenance concept to be found. It has also been found that the Stern-Geary equation which is often used to calculate corrosion current densities and material loss of the reinforcement from linear polarization (LPR) measurements, doesn’t seem very feasible if used on reinforced concrete structures, as there appears to be a dominant influence of macro cell corrosion over the corrosion model of a homogenous mixed electrode (for which the Stern-Geary equation applies), and the true corrosion current densities may be either larger or (very often) much smaller than those calculated from Stern-Geary. This is not a new observation, and the findings will be discussed for several project cases.

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.

Tafel Slopes and Corrosion Rates from Polarization Resistance Measurements

CORROSION ◽  
1973 ◽  
Vol 29 (10) ◽  
pp. 397-402 ◽  
Author(s):  
FLORIAN MANSFELD
Keyword(s):  
Experimental Data ◽  
Time Dependence ◽  
Polarization Resistance ◽  
Corrosion Potential ◽  
Corrosion Current ◽  
Observation Time ◽  
Least Square ◽  
Corrosion Rates ◽  
Tafel Slopes ◽  
Good Agreement

Abstract A new analysis of polarization curves in the non-Tafel region in the vicinity of the corrosion potential is described which allows calculation of the polarization resistance (Rp) and the Tafel slopes (ba and bc). From these data instantaneous corrosion rates are calculated. Experimental data for the system Fe/1N H2SO4 are analyzed by the proposed method and by computer least square analysis. The good agreement observed suggests that all important corrosion parameters (corrosion potential, corrosion current, Tafel slopes) can be obtained by the proposed analysis. These parameters are used for mechanistic considerations which explain the observation time dependence of corrosion potential and corrosion current.

scholarly journals An electrochemical method to investigate the effects of compound composition on gold dissolution in thiosulfate solution

2020 ◽  
Vol 9 (1) ◽  
pp. 496-502 ◽  
Author(s):  
Zhaohui Zhang ◽  
Bailong Liu ◽  
Mei Wu ◽  
Longxin Sun
Keyword(s):  
Dissolution Rate ◽  
Current Density ◽  
Polarization Resistance ◽  
Electrochemical Method ◽  
Corrosion Current Density ◽  
Corrosion Potential ◽  
Corrosion Current ◽  
Gold Dissolution ◽  
Tafel Polarization ◽  
Edta Solution

AbstractThe electrochemical behavior of gold dissolution in the Cu2+–NH3–S2O32−–EDTA solution has been investigated in detail by deriving and analyzing the Tafel polarization curve, as this method is currently widely implemented for the electrode corrosion analysis. The dissolution rate of gold in Cu2+–NH3–S2O32−–EDTA solution was determined based on the Tafel polarization curves, and the effects of various compound compositions in a Cu2+–NH3–S2O32−–EDTA mixture on the corrosion potential and corrosion current density were analyzed. The results showed that the corrosion potential and polarization resistance decreased, whereas the corrosion current density increased for certain concentrations of S2O32−–NH3–Cu2+ and EDTA, indicating that the dissolution rate of gold had changed. The reason for promoting the dissolution of gold is also discussed.

scholarly journals Microstructure of Al-5Cu-1Li-0.6Mg-0.5Ag-0.5Mn Alloys

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 37
Author(s):  
Wenzheng Chen ◽  
Wenlong Zhang ◽  
Dongyan Ding ◽  
Daihong Xiao
Keyword(s):  
Mechanical Properties ◽  
Corrosion Current Density ◽  
Corrosion Potential ◽  
Aging Treatment ◽  
Corrosion Current ◽  
Homogenization Temperature ◽  
Tafel Polarization ◽  
Al2cu Phase ◽  
Different Temperatures ◽  
Microstructural Optimization

Microstructural optimization of Al-Li alloys plays a key role in the adjustment of mechanical properties as well as corrosion behavior. In this work, Al-5Cu-1Li-0.6Mg-0.5Ag-0.5Mn alloy was homogenized at different temperatures and holding times, followed by aging treatment. The microstructure and composition of the homogenized alloys and aged alloys were investigated. There were Al7Cu4Li phase, Al3Li phase, and Al2CuLi phases in the homogenized alloys. The Al7Cu4Li phase was dissolved with an increase in homogenization temperature and holding time. Al2Cu phase and Al2CuLi phase coarsened during the homogenization process. The alloy homogenized at 515 °C for 20 h was subjected to a two-stage aging treatment. Peak-age alloy, which had gone through age treatment at 120 °C for 4 h and 180 °C for 6 h, was mainly composed of α-Al, Al20Cu2Mn3, Al2CuLi, Al2Cu, and Al3Li phases. Tafel polarization of the peak-age alloys revealed the corrosion potential and corrosion current density to be −779 mV and 2.979 μA/cm2, respectively. The over-age alloy had a more positive corrosion potential of −658 mV but presented a higher corrosion current of 6.929 μA/cm2.

scholarly journals Efficiency of Organic Corrosion Inhibitors Derived from Thai-Bael Fruit Extract for Preventing Corrosion in Carbon Steels

2020 ◽  
Vol 32 (8) ◽  
pp. 2043-2050
Author(s):  
Phattarasuda Manantapong ◽  
Nattanon Chaipunya ◽  
Suttipong Wannapaiboon ◽  
Prae Chirawatkul ◽  
Worawat Wattanathana ◽  
...  
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Steel Surface ◽  
Electrochemical Impedance ◽  
Protective Layer ◽  
Corrosion Current ◽  
Carbon Steels ◽  
Fruit Extract ◽  
Polarization Measurements ◽  
Hcl Solution

The inhibiting action of Thai-bael fruit extract at room temperature on hot-rolled steel in 1M HCl solution was studied. The chemical functional groups of the green inhibitors were characterized by Fourier-transformed infrared spectroscopy. The electrochemical activities of steel surface were investigated through linear polarization measurements, electrochemical impedance spectroscopy, surface assessment techniques based on optical microscopy and X-ray absorption spectroscopy. Electrochemical testing samples have been prepared in the form of square plates with the size 1 × 1 cm2. The organic corrosion inhibitor extract from Thai-bael fruit has shown the smallest corrosion current density (Icorr) of 114.8 μA cm-2 and corrosion potential (Ecorr) of -424.6 mV, compared with standard Ag/AgCl electrode potential. In comparison, similar tests in the bare HCl solutions yielded Icorr = 882.4 mA cm-2 and Ecorr = -445.8 mV. The mixed-type corrosion inhibiting behaviour was evidenced in the results of the polarization measurements. Electrochemical impedance spectroscopy reveals that the resistance to charge transfer due to the presence of the extracts has been increased by about four times that of the same test on the bare HCl solution, indicating the formation of a protective layer. The adsorption of the organic molecules near the steel-electrolyte interface is evident in the decreasing double-layer capacitance with the enhancing concentration levels of the extract. This latter finding supports the displacement of the water molecules by means of the adsorption of the inhibitors on the steel surface. The optical images of steel surface before and after being immersed in HCl solution also showed pieces of evidence of corrosion retardation. XANES study as well as the linear combination fitting revealed that the samples immersed in HCl solutions with Thai-bael fruit extract possess less Fe3+ compositions. All tendencies across the four examinations indicate that Thai-bael fruit extract could potentially inhibit the corrosion reaction of steel electrodes in the acidic solution.

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