Pitting and Crevice Corrosion Resistance of Stainless Steels ASTM G48
ASTM G48 describes laboratory tests for comparing the resistance of stainless steels and related alloys to the initiation of pitting and crevice corrosion by the use of Ferric Chloride Solution. The ASTM G48 test is frequently used for corrosion testing within the metal industries.
When stainless steels and related alloys are exposed to an oxidizing chloride environment, the ASTM G48 test method provides the processes for determining their resistance to pitting and crevice corrosion. Stainless steel pitting corrosion resistance can be quickly assessed using ASTM G48 testing in ferric chloride solution. The effects of alloying additives, heat treatment, and surface finishes on pitting and crevice corrosion resistance can also be determined with this test.
In ASTM G48, six procedures are described and identified as Methods A, B, C, D, E, and F:
Method A— Ferric chloride pitting test Method B— Ferric chloride crevice test Method C— Critical pitting temperature test for nickel-base and chromium-bearing alloys Method D— Critical crevice temperature test for nickel-base and chromium-bearing alloys Method E— Critical pitting temperature test for stainless steels Method F – Critical crevice temperature test for stainless steels
However, all tests follow the basic approach of Method A. A sample of the metal is immersed in the acidic ferric chloride solution, typically for 24 to 72 hours, before examining either the relative weight loss or the presence of pits. The test is performed at a set temperature, dependent upon the alloy. Results will usually show zero corrosion, reported as 0g/m2 of the test piece. This indicates an optimized microstructure, with a balance of austenite and ferrite grain, achieved with appropriate solution annealing and quenching processes.
A test specimen 25 by 50 mm (1 by 2 inches) is recommended as a standard size.
Resistance of stainless steel is reported in SI units and is considered standard.