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51318-11243-Applicability of ASTM G28 testing

There appears to be a need for long-term service data for wrought and welded materials with grain boundary precipitation, which can then be compared with ASTM G28 or ASTM A262 data to provide confidence in utilizing such materials.

Product Number: 51318-11243-SG
Author: Briony Holmes / Kasra Sotoudeh
Publication Date: 2018
Industry: Test Method
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It is common practice to perform intergranular corrosion testing in accordance with ASTM (1) G28 on solid solution nickel alloys, e.g. UNS N08825 (Alloy 825) and UNS N06625 (Alloy 625). The results of such tests are applied widely as acceptance tests for parent and welded materials, and as such are essentially used to confirm the suitability of these materials for service. The ASTM G28 test has been used in this way successfully in many cases. However, there are necessarily limitations in the potential applicability of standard tests because the mechanism of corrosion in the service environment may be different than that targeted in the standard test, due to the difference between the actual service environment and the test solution. Indeed, there have been recent instances in TWI’s experience where the acceptance test performance has been unacceptable, but the service performance has been acceptable. The applicability of ASTM G28 tests will be reviewed.

Key words: intergranular corrosion, nickel alloys, sensitization, test method, G28, applicability, weld.

 

It is common practice to perform intergranular corrosion testing in accordance with ASTM (1) G28 on solid solution nickel alloys, e.g. UNS N08825 (Alloy 825) and UNS N06625 (Alloy 625). The results of such tests are applied widely as acceptance tests for parent and welded materials, and as such are essentially used to confirm the suitability of these materials for service. The ASTM G28 test has been used in this way successfully in many cases. However, there are necessarily limitations in the potential applicability of standard tests because the mechanism of corrosion in the service environment may be different than that targeted in the standard test, due to the difference between the actual service environment and the test solution. Indeed, there have been recent instances in TWI’s experience where the acceptance test performance has been unacceptable, but the service performance has been acceptable. The applicability of ASTM G28 tests will be reviewed.

Key words: intergranular corrosion, nickel alloys, sensitization, test method, G28, applicability, weld.

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