Intergranular corrosion of stainless steels

Osozawa, K., Metallurgical Aspects of Intergranular Corrosion of Stainless Steel , Boshoku Gijutsu, 22, 267 (1973) C.A., 80, 85981V... 

Corradi and Gasperini claimed that the potentiostatic method was more effective and simpler than the Strauss test for determining intergranular corrosion of stainless steels, and suggested that the method may lend itself for use on finished equipment in service as a non-destructive test. 

Fig. 28. Micrographs of a fractured specimen, showing numerous small cracks on the gauge length (enlarged in (b)), and intergranular fracture (c) enlargement of fracture surface [57]. Copyright 1991. Electric Power Research Institute/EPRl ER-7247. Intergranular Corrosion of Stainless Steel. Vol. 1 Mechanism of Crack Initiation. Reprinted with permission.

Intergranular Corrosion of Stainless Steel, Vol. 1 Mechanism of Crack Initiation, EPRI ER-7247, Electric Power Research Institute, Palo Alto, CA (March 1991). 

Intergranular corrosion of stainless steel does not occur in all environments. Thus inferior corrosion resistance at the grain boundaries does not necessarily lead to practical problems. However, a reasonable aim is to obtain corrosion properties at the welds equal to those elsewhere on the steel surface, in order to utilize the material as much as possible. 

Dundas HJ, Bond AP. Niobium and titanium requirements for stabilization of ferritic stainless steels. In Steigerwald RF, editor. Intergranular Corrosion of Stainless Steel. STP 656. Philadephia ASTM, 1978. 

A low carbon concentration reduces the risk of intergranular corrosion of stainless steels that results firom the precipitation of chromium carbides at the grain boundaries (Chapter 7). The presence of Ti, Nb or Ta in small amounts (stabilized stainless steels) also works this way, because these elements form particularly stable carbides. 

As described before, intergranular corrosion of stainless steels occurs when the material is sensitized. This condition produces a chromium-depleted envelope around each grain, which is less corrosion-resistant. This results in intergranular corrosion of the stainless steel in certain environments. The two ASTM standards that describe how to test stainless steels for susceptibility to this form of corrosion are ASTM A 262 and A 763. A third standard, G 28, is applicable to nickel-rich, chromium-bearing alloys. 

Austenitic Stainless Steels—Determination of resistance to intergranular corrosion of stainless steels— Part 1 Austenitic and ferritic-austenitic (duplex) stainless steels—Corrosion test in nitric acid medium by measurement of loss in mass (Huey test)... 

AFNOR (1998) NF EN ISO 3651-1 1998. Determination of Resistance to Intergranular Corrosion of Stainless Steels. Part 1 Austenitic and Ferritic-Austenitic (Duplex) Stainless Steels. Corrosion Test in Nitric Acid Medium by Measurement of Loss in Mass (Huey Test), AFNOR, Paris. 

Huey test Corrosion testing in a boiling solution of nitric acid. This test is mainly used to detect the susceptibility to intergranular corrosion of stainless steel. 

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