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.

Subject
Test methods, Materials, Precipitation (solids), Applicability, Materials performance, Nickel based alloys, Micrography, Test environments, Sensitization, Grain boundary, Alloys, Intergranular corrosion, Wrought metals
Keywords:
intergranular corrosion, nickel alloys, sensitization, test method, G28, applicability, weld
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2018
Association for Materials Protection and Performance (AMPP)
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