Standardized
test methods for detecting the susceptibility
of ferritic stainless steels to intergranular
corrosion are described in ASTM A763 (Ref 30).
The methods are similar to those described in
ASTM A262 (Ref 4) for austenitic stainless
steels in that there is an oxalic acid etch test and
three acid immersion tests. The principal difference
between the two standards is the use of
microscopic examination of samples exposed to
the boiling acid solutions. The presence or
absence of grain dropping becomes the acceptance
criterion for these samples.