ASTM G28-02 pdf free download.Standard Test Methods of Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys.
1. 1 These test methods cover two tests as follows:
1 . 1 . I Method A, Ferric Sulfate-Sulfuric Acid Test (3- 10 inclusive)—This test method describes the procedure for conducting the boiling ferric sulfate—50 % sulfuric acid test which measures the susceptibility of certain nickel-rich, chromium-bearing alloys to intergranular corrosion (see Terminology G 15). which may be encountered in certain service environments. The uniform corrosion rate obtained by this test method. which is a function of minor variations in alloy composition, may easily mask the intergranular corrosion components of the overall corrosion rate on alloys N10276, N06022, N06059, and N06455.
1 . 1 .2 Method B, Mixed Acid-Oxidizing Salt Te.s t (Sections
11-18, inclusive)—This test method describes the procedure for conducting a boiling 23 % sulfuric + 1.2 % hydrochloric + 1 % ferric chloride + 1 % cupric chloride test which measures the susceptibility of certain nickel-rich, chromium- bearing alloys to display a step function increase in corrosion rate when there are high levels of grain boundary precipitation.
1.2 The purpose of these two test methods is to detect susceptibility to intergranular corrosion as influenced by variations in processing or composition, or both. Materials shown to be susceptible may or may not be intcrgranularly cormded in other environments. This must he established independently by specific tests or by service experience.
5. Test Solution
5.1 Prepare 600 mL of 50% (49.4 to 50.9 %) solution as follows:
5.1.1 Varning—Protect the eyes and use rubber gloves for handling acid. Place the test flask under a hood.
5.1.2 First, measure 400 mL of Type IV reagent water (Specification D 1193) in a 500-rnL graduate and pour into the flask.
5.1.3 Then measure 236 mL of reagent-grade sulfuric acid (H,S04) of a concentration which must he in the range from 95.0 to 98.0 weight percent in a 250-mL graduate. Add the acid slowly to the water in the flask to avoid boiling by the heat evolved (Note 3). Externally cooling the flask with water during the mixing will also reduce overheating.
NOTE 3—Loss of vapor results in concentration of the acid.
5.1.4 Weigh 25 g of reagent grade ferric sulfate (contains about 75 % Fe, (SO4) (Note 4)) and add to the H,S04 solution. A trip balance may be used.
Nom 4—Ferritic sulfate is a specific additive that establishes and controls the corrosion potential. Substitutions are not pennitted.
5.1.5 Add boiling chips.
5.1.6 Lubricate the ground glass of the condenser joint with silicone grease.
5.1.7 Cover the flask with the condenser and circulate cooling water.
5.1.8 Boil the solution until all ferric sulfate is dissolved.ASTM G28 pdf download.