The electrochemical methods used to test the corrosion of metallic materials under aqueous conditions are frequently used to provide rapid and quantitative information. The ASTM G59 test process offers a powerful dynamic polarization resistance (LPR) test procedure, which facilitates the measurement of the polarization resistance (Rp) of a sample; hence, an approximation of the corrosion current density (icorr). Although the method was originally used to calibrate instrumentation and test techniques, it has a wider range of uses in the ranking of alloys, testing of inhibitors, or in situ corrosion behavior. The main benefit of ASTM G59 is that it is relatively fast to perform, unlike the weight-loss or long-term immersion tests, and is therefore applicable in most industrial and research laboratories.
ASTM G59 Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements
What is ASTM G59?
What is the Scope of ASTM G59?
ASTM G59 standard is a laboratory-level method of determining the polarization resistance of metallic specimens through potentiodynamic scanning of the corrosion potential. The technique allows calibration of electrochemical equipment, evaluation of the general rates of corrosion, and checking of the operator procedure. With the procedure, the reproducible corrosion potentials and polarization resistance measurements are obtained, provided the specified conditions are met.
What Materials Are Commonly Tested With ASTM G59?
The technique is normally used on steels, aluminum alloys, copper, nickel, and titanium-based materials to examine their electrochemical corrosion characteristics in aqueous solutions.
Applications of ASTM G59 in Industry
ASTM G59 testing is common across aerospace, automotive, energy, and marine industries in the assessment of the protective behavior of coatings, inhibitors, and corrosion-resistant alloys.
ASTM G59 Equipment and Sample Preparation
| Test Cell Components | The glass or inert polymer cell with connections for working, reference, and counter electrodes is included, along with a potentiostat for controlled potential measurements. |
| Specimen Preparation | The metallic specimens are prepared by polishing with abrasive papers up to 600 grit, rinsing with distilled water and alcohol, and then drying before immersion to maintain uniformity in surface finish. |
| Specimen Dimensions | The typical size of the specimen is 1 cm² exposed area, mounted in a non-conductive holder with only one face exposed to the electrolyte solution. |
ASTM G59 Testing Procedure and Requirements
| Principle | A small potential sweep (usually ±20 mV around the corrosion potential) is applied to the specimen, and the resulting current is measured to determine polarization resistance. |
| Electrochemical Setup | A three-electrode cell consists of a working electrode (test specimen, a reference electrode (saturated calomel or Ag/AgCl), and a counter electrode (graphite or platinum). |
| Data Analysis | The slope of the potential vs. current plot near the corrosion potential, or E–I curve, is utilized to compute the polarization resistance, Rp, from which corrosion current density, Icorr, is obtained. |
ASTM G59 Test Results and Interpretation
The output of the test is given as polarization resistance (Rp) and corrosion current density (Icorr), which are used to determine the rate of corrosion. A reduced Icorr value is an indicator of increased corrosion resistance. The curves can be plotted to produce polarization curves, which help in understanding anodic and cathodic reactions on the metal surface.
ASTM G59 Related Articles
Other applicable ASTM corrosion testing standards include ASTM G102, which outlines approaches to calculating corrosion rate from electrochemical data, and ASTM G5, which outlines the use of reference electrodes in corrosion testing.
Safety and Best Practices in ASTM G59
The potentiostat must be well grounded, the electrolytes must be handled using protective gloves and eyewear, and the electrodes should be calibrated prior to every test in order to provide accurate and safe operation.
Importance of ASTM G59
ASTM G59 is an important material in the study of corrosion and the qualification of materials. It allows industries to forecast the long-term corrosion behavior by using rapid electrochemical tests, which aid in minimizing material failures and maintenance expenses.
Updated on September 17, 2026
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