Nickel-base alloys polarization measurements

Nickel-base alloys respond well to most electrochemical test techniques and show active-passive behavior in many environments. Due to their rapid repassivation, however, the results obtained with potentiod3mamic techniques can sometimes be affected by scan rate and immersion time prior to starting the test [5,6], Electrochemical techniques are useful for investigating localized corrosion resistance, ASTM G 61, Test Method for Conducting Cyclic Potentio-dynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys, and general corrosion resistance, ASTM G 59, Practice for Conducting Potentiodynamic Polarization Resistance Measurements of nickel alloys. Electrochemical impedance measurement techniques have not been extensively applied to nickel alloys. 

G61-86, Conducting cyclic potentiodynamic polarization measurements for localized corrosion susceptibility of iron-, nickel-, or cobalt-based alloys, Annual Book of ASTM Standards, ASTM International, Philadelphia, Pa., 2000, p. 240, Vol. 3.02. 

ASTM G 61-86, Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys, ASTM International, West Conshohocken, PA, 2003. 

Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys... 

Electrochemical tests provide a means to understand the corrosion process, simulate service conditions, or accelerate evaluation of a material [27]. ASTM G 3, Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing ASTM G 5, Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Polarization Measurements and ASTM G 61, Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys provide background in some of these techniques. 

McKubre and Syrett (1983, 1988) were the first to adapt the method of harmonic analysis for the control of the corrosion rate of cathodically polarized systems. They presented a theoretical description of the problem and developed the measuring technique by making measurements over a wide range of frequencies from 1 Hz to 10 kHz. The method applied by them is known in the literature as harmonic impedance spectroscopy (HIS). It is based on the measurement of the zero, first, second, and third harmonics of the current response of an electrode perturbed by a voltage sinusoid signal. The elaborate mathematical treatment of results theoretically gives the possibility of obtaining admittance data independent of the frequency. The numerical solution of a system of three equations with three unknowns allows the determination of required AE, b, and values, and finally the corrosion current. The authors of the HIS method carried out attempts to determine the corrosion rate of copper-nickel alloys, steel, and titanium under cathodic protec-... 

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