What is the ASTM G48 test?

To give it its full title, ASTM G48 is the “Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution”.

It’s a corrosion test, utilising an aggressive solution of ferric chloride. Although this medium is rarely seen in day-to-day operations, it partly replicates the conditions seen within a corrosion pit in chloride-containing solutions. Therefore, the test has become an accepted measure of the pitting corrosion resistance of stainless steels.

What Does ASTM G48 Involve?

Within the standard, there are several different formats, including the use of a crevice forming device to artificially simulate the presence of an undesirable feature. 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. For instance, 2205 duplex (1.4462, F51) is commonly tested at 25°C (77°F), whilst super duplex stainless steels such as Alloy S32750 (1.4410, F53), Alloy S32760 (1.4501, F55) and Ferralium 255 (1.4507, F61, S32520) are tested at 50°C (122°F). 

Results will usually show zero corrosion, reported as 0g/m2 of the test piece. This indicates an optimised microstructure, with a balance of austenite and ferrite grain, achieved with appropriate solution annealing and quench processes.

Which ASTM G48 Tests Do I Need?

This depends on several factors that can influence your selection. Here are the available pitting and crevice testing methods –

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

For Any Questions, Contact Us Today

At Langley Alloys, our technical team can undertake additional testing including corrosion testing, as defined by customer and end user specifications. If you have any questions about ASTM G48 tests, please do not hesitate to contact us today and we will get back to you as soon as possible.