Experienced in Mechanical, Chemical, Metallurgical, And Corrosion Testing
Intergranular attack (IGA) is a form of corrosion where the boundaries of grains of the material are more susceptible to corrosion than their insides. ASTM A262 is the specification used to detect susceptibility to IGA in austenitic stainless steels. Certain grades (extra low Carbon grades & stabilized grades, such as 304L, 316L, 317L, 321, & 347) require the coupon be sensitized prior to testing.
Method A is a rapid screening where the test specimen is etched in 10% oxalic acid at 1 A/cm2 for 1.5 minutes, then examined at 500X. If the sample has an acceptable etch structure then the sample is considered good and no further testing is necessary.
Method E calls for the test coupon to be immersed in a boiling aqueous solution of acidified copper/copper sulfate for 15 hours minimum with subsequent bending developing no cracks or other evidence of disintegration.