best types of metal for electrodes ? [resolved]

Comments

• wjcroft Mount Shasta, CA

  February 2021

  The best performance and stability is from Ag-AgCl type electrodes. Best in this class are the sintered electrodes. But for most purposes the normal Ag-AgCl is fine; these are typically plastic, plated with silver, then chlorided.

  Gold would probably be next, but since it is plated on top of tin, any chips or cracks can cause galvanic (battery) type effects. Solid silver is good. Solid tin as well, but it has the least stability.

  Nickel, copper, steel, are generally not used. I believe for stability and galvanic reasons.

  William
• wjcroft Mount Shasta, CA

  February 2021

  This is a good paper. SCP Slow Cortical Potentials EEG requires excellent stability of electrodes. So this study was made.

  https://www.researchgate.net/publication/7942803_Tallgren_P_Vanhatalo_S_Kaila_K_Voipio_JEvaluation_of_commercially_available_electrodes_and_gels_for_recording_of_slow_EEG_potentials_Clin_Neurophysiol_116799-806

  Evaluation of commercially available electrodes and gels for recording of slow EEG potentials. To test the applicability of different types of commercially available electrodes and electrode gels or pastes for recording of slow EEG potentials. Experiments were carried out on six types of reusable electrodes (silver, tin and gold cup electrodes, sintered silver-silver chloride (Ag|AgCl), platinum, stainless steel), six disposable Ag|AgCl electrode models, and nine gels or pastes. We studied the parameters, which are critical in slow-potential recording, such as polarization, initial and long-term stability and low-frequency noise. The best results were obtained with the reusable sintered Ag|AgCl electrodes. The six disposable Ag|AgCl electrode models also proved to have appropriate electrical properties. Other types of reusable electrodes suffered from diverse degrees of polarization, baseline drift, low-frequency noise, high resistance, and changes in properties due to wear and tear. Seven out of nine gels or pastes contained a significant amount of chloride, which is a prerequisite for DC stability of Ag|AgCl electrodes, whereas the absolute concentration of chloride had little effect. Direct current (DC) coupled recording of EEG is critically dependent on the choice of electrode and gel. Our results provide rigorous criteria for choosing DC-stable electrodes and gels for DC-coupled or long time-constant AC-coupled recordings of slow EEG potentials.