Pitting and Crevice Corrosion testing is performed to identify and examine the extent of corrosion that has occurred, in order to measure and predict the remaining life in the metal part.

Both are localized forms of attack, which occur at shielded areas on the metal surfaces exposed to certain specific corrosive environments.  Crevice corrosion occurs very frequently in engineering structures, particularly with threaded or riveted joints, gasket fittings, welded lap joints and coiled or stacked sheets. The corrosion primarily affects passive type alloys.

All of these tests may be used to determine the effects of alloying additives, heat treatment and surface finishes on pitting and crevice corrosion resistance.

 

ASTM G46 Aids in the selection of test methods for evaluation and examination

 

ASTM G48 Method A to D expose samples to a highly oxidizing Ferric Acid Chloride environment.  Methods A and C refer to pitting corrosion only, Methods B and D pertain to crevice corrosion.  Generally, specimens tested to Method B can also be evaluated according to Method A. Methods C and D are employed to determine the critical pitting and critical crevice temperature, respectively.

 

ASTM G78 Is an immersion test for stainless steels and related nickel-based alloys in seawater and other chloridecontaining environments.

 

ASTM A923 Method C covers Ferric Chloride Corrosion testing and is a modification of G48 Method A.  The modifications consist of adjustment of the pH of the test solution and the requirement to test the full thickness.  This method is normally used for Duplex Stainless steels.

 

ISO 8565 Is a rating system used for the evaluation of pitting/crevice corrosion