Pitting and crevice corrosion can be challenging to detect and predict, so understanding the risk factors of corrosion and susceptibility of a material can help anticipate issues before they arise. Element offers pitting and corrosion testing for your stainless steel/alloys and metal products used in many industries, including Energy, Aerospace, Infrastructure, Environmental, and Industrials.
If a material exhibits holes or gaps on its surface, pitting or crevice corrosion may be the culprit. Pitting corrosion is characterized by small holes, and crevice corrosion occurs where two materials meet.
Pitting can be one of the most dangerous types of corrosion. It isn't straightforward to anticipate, may occur very rapidly, and may only produce localized corrosion, with the vast majority of the surface remaining unaffected.
Pitting corrosion testing to ASTM G48 A, C and E test methods
Element performs pitting corrosion testing following ASTM G48 A at test temperature, typically up to 60°C. The test involves the exposure of the materials in a 6 wt % ferrite chloride solution for test durations of 72 hours (typically 24 hours). A variation of the ASTM G48-A test used for duplex stainless steels is the ASTM A923 method – C test.
Critical Pitting Temperature (CPT) is the technique used to determine the temperature at which the material produces pitting. In CPT, specimens are exposed for 72-hour periods to increase temperatures incrementally. The temperature is increased until pitting is observed, which is recorded as the Critical Pitting Temperature (CPT).
As an alternative to the G48 methods, the onset of pitting can be determined using the electrochemical test method described in ASTM150. In this method, the specimen is polarized, and the temperature of the solution increased until the CPT is detected.
Crevice corrosion testing to ASTM G48 B, D, and F test methods
Element performs crevice corrosion testing in accordance with ASTM G48 B at the test temperature, typically up to 60°C. The test involves the exposure of the materials in a 6 wt % ferrite chloride solution for test durations of 72 hours (typically 24 hours).
The temperature at which crevices initiate can be determined using a Critical Crevice Temperature (CCT) test method. In ASTM G48, there are two test methods; one for stainless steel (method – D) and one for nickel alloys (method – F). Using CCT, specimens are exposed for 72 hour periods to increase temperatures incrementally until a crevice is observed.
Our in-depth knowledge of industry standards and corrosion testing programs allow us to advise you on the most suitable test method for your materials. Choosing the correct test method is crucial to achieve positive test results first time right and avoid costly delays in your project schedules, saving you time and money as a result.
Crevice corrosion ASTM G78 test method
Element offers crevice corrosion testing in accordance with ASTM G78 at the test temperature, typically up to 60°C. The test involves the application of castellated washers (MCAs) to the surface of the specimen, usually with 20 contact points on each washer in a chloride-containing environment (seawater) for a test duration of up to 30 hours (typically 24 hours). At the end of the test period, the specimens are examined for evidence of crevice corrosion.
Evaluation of pitting and crevice corrosion
Element’s corrosion laboratories use ASTM G46 in the assessment of pitting and crevice corrosion. More detailed evaluation can also be conducted using Electron Scanning Microscopy.
The Element advantageWith state-of-the-art facilities and access to a global network of expertise, Element's materials testing and corrosion labs provide many different test methods for testing pitting and crevice corrosion in the USA, Europe, Middle East, Asia, and Africa. For more information about how we perform pitting and crevice corrosion testing, or to request a quote, contact us today.
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