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Electrochemical Testing

All corrosion is an electrochemical process of oxidation and reduction reactions.  Therefore, controlled electrochemical experimental methods can be used to characterize the corrosion properties of metals and metal components in combination with various electrolyte solutions or soil environments. The corrosion characteristics are unique to each metal/solution system. Matergenics performs electrochemical test procedures to determine or predict the corrosion rates of metals in a wide range of environments. Among the electrochemical techniques  are the ASTM / NACE techniques, Cyclic Polarization, Impedance Spectroscopy,  linear polarization tests , electrochemical tests for hydrogen permeation, real-time corrosion predictions for materials, and others. Environments include corrosive solutions, soil environments and atmospheric corrosion monitoring. The following plot exhibits a case example for using electrochemical technique (ASTM G61All corrosion is an electrochemical process of oxidation and reduction reactions. As corrosion occurs, electrons are released by the metal (oxidation) and gained by elements (reduction) in the corroding solution. Because there is a flow of electrons (current) in the corrosion reaction, it can be measured and controlled electronically. Therefore, controlled electrochemical experimental methods can be used to characterize the corrosion properties of metals and metal components in combination with various electrolyte solutions. The corrosion characteristics are unique to each metal/solution system.) for selection of  materials in acidic chlorides. The plot clearly indicates Type 304 stainless steel is not a proper material selection for acidic chloride environments

ASTM G61- Materials Selection in Corrosive Environments. Standard Test Method for Conducting Cyclic Potentio-dynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys

 

image002_largeCyclic Polarization Measurements—Experimental Procedure and Evaluation of Test Data

 

There are two basic methods of electrochemical measurement for materials selection and evaluation:

  • Applying external current to generate electrochemical data away from the free corrosion potential. These tests generally explore the relationship between electrochemical potential and current
  • Electrochemical measurements at the free corrosion potential, without the application of an external current.

Matergenics has six Gamry systems to meet your electrochemical testing requirements

Electrochemical corrosion tests include the following techniques:

  • Linear polarization resistance (LPR) measurements
  • Potentio-dynamic polarization curves
  • Electrochemical potentio-kinetic reactivation (EPR) measurements for intergranular corrosion
  • Current vs time curves (at a given potential)
  • Electrochemical impedance spectroscopy (EIS)
  • Harmonic analysis
  • Electrochemical noise (EN) measurements

Samples for electrochemical corrosion testing must utilize electrical conductors and must be small enough to fit in the polarization cell. Components can be tested as a whole or as a smaller section. Metal coupons are specially prepared for some tests.

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EIS technique is used to evaluate materials and coatings in corrosive environments. EIS measures impedance of the coating at different frequencies. This is an indication of barrier effect of the coating. Barrier coating will exhibit high impedance in corrosive exposures. Changes  in electrical properties determined by EIS experiments have been found to closely resemble long-term performance of coatings.This way EIS method can detect deterioration at metal/coating interfaces well before defects become visible, and with greater accuracy than artificial testing methods such as salt spray.

 

Electrochemical Corrosion Cells

The above photos show various  “Electrochemical Corrosion Cells” at our electrochemical laboratory  to test corrosion of bare or painted test coupons

Impedance Measurements on Organic Coatings on Mild Steel in Sodium Chloride Solutions Impedance Spectroscopy provides very useful information about protective coatings. The above plots clearly exhibits how good the coating is!

An Electrochemical Technique to Measure Diffusible Hydrogen in Metals  We have four Hydrogen Permeation Cell Set ups  to Determine Hydrogen Diffusivity , permeability Through Metals

Electrochemical Techniques used for Corrosion Measurements: 

Scanning Reference Electrode Techniques in Localized Corrosion

Potential Dependence of Localized Corrosion in Iron

A Method for Quantifying the Initiation and Propagation Stages of Crevice Corrosion

A Strain-Control Technique for Assessing the Corrosion-Fatigue Sensitivity of Stainless Steels

Potential and Strain-Rate Effects in Slow Strain-Rate Stress Corrosion Cracking of Type 304 Stainless Steel in 35 Percent Magnesium Chloride at 120°C

Corrosion and Electrochemical Behavior of Iron-Chromium-Nickel Alloys in Concentrated Sulfuric Acid Solutions

Electrochemical Impedance Techniques in Corrosion Science

Alternating-Current Impedance Measurements Applied to Corrosion Studies and Corrosion-Rate Determination

A Corrosion Monitor Based on Impedance Method

Impedance Measurements on Organic Coatings on Mild Steel in Sodium Chloride Solutions

Digital Faradaic Impedance Measurements on Corroding Copper in Acid Solutions

Evaluation of Electrochemical Techniques for Monitoring of Atmospheric Corrosion Phenomena

Practical Experience with an Electrochemical Technique for Atmospheric Corrosion Monitoring

An Electrochemical Technique to Measure Diffusible Hydrogen in Metals (Barnacle Electrode)

Cyclic Polarization Measurements—Experimental Procedure and Evaluation of Test Data

Application of Potentiokinetic Hysteresis Technique to Characterize the Chloride Corrosion of High-Copper Dental Amalgams

Direct Measurement of the Corrosion Current for Oxygen-Reduction Corrosion

Electrochemical Behavior of Carbon Steel in Fused Salts

Galvanic Corrosion of Copper Alloys

Electrochemical Investigation of Cavitation-Corrosion Damages of a Pump Casing

A Method of Evaluating Polarization Curves for Stainless Steel via a Simple Passivation Model

Effect of Large Voltage Modulations on Electrodes Under Charge-Transfer Control

Progress in Mini-Potentiostat Development for Corrosion Testing

A Microprocessor-Based Corrosion Measurement System

We are here to help

We respond to all customers promptly by sending a technical proposal to address testing, investigation and the proposal costs. If we need more information, our engineers will contact you.

Whether you are a large corporation or a small enterprise, we will provide you with the attention you need and deserve. In so doing, we hope to work with you for many years to come.

Please call Dr. Zee at 412-952-9441 or 412-788-1263 and let us know how we can assist you in your electrochemical or corrosion investigation. Alternatively, you can send your request to info@matergenics.com.

Looking forward to hearing from you!

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