Corrosion Challenges Solved – Pitting and Crevice Corrosion Testing

Testing for crevice corrosion and pitting are significant methods for determining how susceptible a material is to localized corrosion in a given environment. Because localized corrosion occurs at specific locations and causes the development of pits or crevices, which can quickly pierce through the material, it can be more harmful than uniform corrosion. Methods of testing aid in determining a material’s resistance to these types of corrosion.

Typical Techniques For Testing For Pitting And Crevice Corrosion

Potentiostatic Testing: In potentiostatic testing, a sample is submerged in an acidic solution while being subjected to a set potential (voltage). This aids in preserving a consistent potential at the working electrode (the sample), which, under regulated circumstances, can promote pitting corrosion. The critical pitting potential (CPP) can be calculated and the current response can be observed.

Electrochemical Impedance Spectroscopy (EIS): EIS calculates a material’s impedance in relation to frequency when it is exposed to corrosive conditions. Changes in the impedance response can be used to identify pitting and crevice corrosion. It is possible to learn more about the mechanisms of corrosion and the beginning of pitting by studying the EIS data.

Cycle Polarization Testing: In a corrosive solution, the electrode potential is cycled between predetermined levels during a cycle polarization test. The corrosion potential, corrosion current, and repassivation potential can all be calculated using this information. Pitting susceptibility is frequently related to the polarization curve’s form.

Salt Spray Testing (ASTM B117): This method is frequently used to evaluate a material’s resistance to both general and localized corrosion, including pitting. It entails spraying a controlled chamber with salt water on the test specimen for a predetermined amount of time. Evaluations are made of pit formation and growth.

Examining a material’s resistance to corrosion in crevices, which can happen between two closely adjacent surfaces, is the focus of crevice corrosion testing. The sample is frequently subjected to corrosive conditions while being exposed to fissures made by gaskets, washers, or shims during tests. Crevice corrosion severity can be determined visually or by calculating weight loss.

In order to examine localized corrosion at the micrometer or nanoscale scale, a specialized technique called scanning electrochemical microscopy (SECM) is used. It can offer details regarding the beginning and development of pits on a material’s surface.

Laboratory Immersion Testing: In this technique, samples are submerged for a predetermined amount of time in a corrosive solution. The degree and traits of pitting or crevice corrosion following exposure are examined by visual inspection, metallography, or scanning electron microscopy (SEM).

Accelerated Pitting Tests: By exposing the material to a critical chloride concentration, accelerated tests like the ASTM G48 test are intended to accelerate pitting corrosion. The material’s resistance to pitting is assessed under controlled test circumstances and duration.

Infinita Lab offers corrosion testing services for metal and alloy products in various industries. They use ASTM G48 A, C, and E procedures for pitting and crevice corrosion, with pitting testing conducted at temperatures up to 60°C. The Critical Pitting Temperature (CPT) method is used to determine the temperature at which pitting occurs. The ASTM150 electrochemical test method can be used instead of G48 procedures to detect the onset of pitting. Crevice corrosion testing is conducted at temperatures up to 60°C using ASTM G48 B, D, and F standards. The Critical Crevice Temperature (CCT) test is used to determine the temperature at which cracks begin to form. Infinita Labs uses the ASTM G46 standard for pitting and crevice corrosion analysis, with Electron Scanning Microscopy for in-depth analysis. Their cutting-edge equipment and global network of experts provide a wide variety of test methods for evaluating corrosion.

Video 01: 05 – Corrosion failures: pitting and crevice corrosion