The Power of  Electrochemical Corrosion Testing 

Electrochemical corrosion testing is a method to assess a metal’s resistance to corrosive environments. This involves tracking the electrochemical activity of a specimen exposed to a corrosive solution, with the reaction between materials and surroundings being controlled and measured. Targeted electrolyte solutions can be used to model long-term exposure and predict corrosion. Electrochromic corrosion is used in medical equipment evaluation, raw material assessment, effects analysis, processing effects comparison, and evaluating bimetallic combinations for galvanic corrosion.

Test Procedures For Electrochromic Corrosion

Measurements of Cyclic Polarization Potential (ASTM F2129)

It is useful for gauging how a metal or alloy would fare in a chemical environment. It entails measuring the current produced by cycling through a series of electrode potentials and then returning to the initial potential at a constant scan rate. Corrosion potential, corrosion current density, and passivation potential can all be determined from the collected data.  The corrosion reaction kinetics and corrosion rate of the metal can be deduced from the test’s polarization curves. The study of localized corrosion events like pitting and stress corrosion cracking benefits greatly from the use of CPP. 

Alloys of Iron, Nickel, and Cobalt: Their Propensity to Corrode (G61)

The potential of the metal or alloy specimen is measured at regular intervals while it is immersed in a corrosive solution. To conduct the test, a sample of the alloy is submerged in a solution containing a predetermined concentration of sulfuric acid and ferric sulfate. The specimen’s potential is then monitored at set intervals for a given time period, usually between 24 and 72 hours. The rate of corrosion of an alloy can be calculated from the potential values that have been measured. The G61 test is helpful for gauging an alloy’s ability to withstand corrosion in simulated industrial circumstances, such as those involving sulfuric acid solutions. Alloys’ propensity to experience intergranular corrosion, pitting corrosion, and stress corrosion cracking can be ascertained with the help of this test. The corrosion resistance of alloys used in applications where they are exposed to corrosive conditions is typically evaluated using the G61 test, which is widely used in the aerospace, chemical processing, and oil and gas industries. Corrosion inhibitors and other treatments for preventing corrosion of these metals can also be assessed using this test.

ASTMG71: Galvanic Corrosion

Two metal specimens are brought into close proximity and held there with a special holder. Weighing the specimens before and after immersion in an electrolyte solution, or employing electrochemical techniques like potentiodynamic polarization or electrochemical impedance spectroscopy, allows us to calculate the anode’s corrosion rate. Different metal combinations can be tested for their resistance to galvanic corrosion, and the impact of environmental conditions like temperature and pH can be measured. If you want to know how well coatings or other treatments protect dissimilar metals from galvanic corrosion, this test can do that, too.

Medical Implant Galvanic Corrosion (F3044)

Medical metal implants’ susceptibility to galvanic corrosion when in contact with other metallic body parts is measured using ASTM’s F3044 standard test procedure. The possibility of medical implant failure due to corrosion is evaluated by subjecting them to conditions that mimic those found inside the human body. When two dissimilar metals in the body form an electrochemical cell, the corrosion of one metal is accelerated. The galvanic current and corrosion rate are determined by measuring the electrical potential between implanted metal components while the implant is submerged in simulated bodily fluid (F3044). Corrosion resistance is a must for medical implants to avoid potential problems.

Among the nondestructive methods available for gauging the corrosion rate of metals is the Linear Polarization Resistance (ASTM G59) LPR test. The polarization resistance of a metal surface in a corrosive environment is measured using the LPR technique. LPR testing involves applying a modest potential (voltage) to a metal specimen immersed in a corrosive solution and measuring the consequent current. The LPR method may calculate the polarization resistance, which is directly proportional to the corrosion rate, by observing the metal’s response to a current. The LPR technique is a fast and reliable methodology for determining a metal’s resistance to corrosion in aqueous solutions, seawater, and other industrial process fluids. The efficiency of corrosion inhibitors and coatings can also be judged with this method. When determining a component’s corrosion resistance, sectors like aerospace, automotive, and oil & gas frequently employ the LPR test method. It’s also used to determine which metals are best for building structures and public infrastructure, as well as any other uses where corrosion resistance is important.

Video 01: Electrochemical corrosion