Impedance-based measurements, scanning

Another impedance-based imaging technique for laterally resolved characterization of thin films or electrochemical systems is Scanning Photo-induced Impedance Microscopy (SPIM) [44]. It is based on photocurrent measurements at field-effect structures. In their simplest arrangement, field-effect structures consist of a semiconductor substrate with a thin insulator, and a gate electrode. This gate electrode can be a metal film resulting in the structure Metal Insulator Semiconductor (MIS) or, alternatively. Electrolyte Insulator Semiconductor structures are used, in which the electrolyte is in direct contact with the insulator, and a reference electrode is required to fulfill the function of the gate electrode. 

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. 

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