Nickel-rich chromium-bearing alloys

Recommended practice for applying statistics to analysis of corrosion data Practice for operating light- and water-exposure apparatus (carbon-arc Type) for exposure of nonmetallic materials Method for detecting susceptibility to intergranular attack in wrought nickel-rich, chromium-bearing alloys... 

ASTM Standard G 28, Standard Test Methods of Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel Rich, Chromium-Bearing Alloys, Annual Book of ASTM, 1999, 03.02. 

Test Methods for Detecting Susceptibility to Intergrtinular Attack in Wrought Nickel-Rich, Chromium-Bearing Alloys. 

The term stainless alloys includes the austenitic and ferritic stainless steels with 12 % or more chromium and certain austenitic nickel-rich chromium-bearing alloys. From this section through the discussion on the oxalic acid etch test, the text is an update and condensation of material in Ref 9. AU figm es are from this publication except where other references are shown. The latter are reprinted with permission, copyright NACE International. All rights reserved by NACE. 

In 1974, the ferric sulfate test was applied by Brown [SI] to other nickel-rich, chromium-bearing alloys and found to be applicable for detecting susceptibility to intergranular attack in alloys G, 20 Cb-3, 600, 625, 800, and 825 (Table 1). All of these alloys have been incorporated in ASTM G 28, Practice A (Table 7). 

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. 

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