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IGC FLANGE ASTM A262-Intergranular corrosion test(IGC)

Intergranular corrosion is sometimes also called "intercrystalline corrosion" or "interdendritic corrosion".

All the flanges from Longrun can meet the requirements according to ASTM A262 or DIN EN ISO 3651-2


Sample of test report for stainless steel flange-ASTM A262 IGC 

Here,let's see ASTM A262-Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
 
These practices cover the following five tests:
Practice A: Oxalic Acid Etch Test for Classification of Etch Structures of Austenitic Stainless Steels
 
Practice B—Ferric Sulfate–Sulfuric Acid Test or Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels. 
 
Practice C —Nitric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels.
 
Practice E—Copper–Copper Sulfate–Sulfuric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels.
 
Practice F—Copper–Copper Sulfate–50% Sulfuric Acid for Detecting Susceptibility to Intergranular Attack in Molybdenum-Bearing Cast Austenitic Stainless Steels.
 
Susceptibility to intergranular attack associated with the precipitation of chromium carbides is readily detected in all six tests.
Extra-low–carbon grades, and stabilized grades, such as304L,316L,317L,321,and347,are tested after sensitizing heat treatments at 650 to 675°C (1200to1250°F), which is the range of maximum carbide precipitation . These sensitizing treatments must be applied before the specimens are submitted to the oxalic acid etch test. The most commonly used sensitizing treatment is 1h at 675°C (1250°F).
 
The oxalic acid etch test is a rapid method of identifying, by simple etching, those specimens of certain stainless steel grades that are essentially free of susceptibility to intergranular attack associated with chromium carbide precipitates. These specimens will have low corrosion rates in certain corrosion tests and therefore can be eliminated (screened) from testing as “acceptable.”
 
The use of these classifications depends on the hot acid corrosion test for which stainless steel specimens are being screened by etching in oxalic acid and is described in each of the practices. Important characteristics of each of these tests are described below
 
Practice B—Ferric Sulfate–Sulfuric Acid Test is a 120-h test in boiling 50% solution that detects susceptibility to intergranular attack associated primarily with chromium carbide precipitate. It does not detect susceptibility associated with sigma phase in wrought chromium-nickel-molybdenum stainless steels (316,316L,317, 317L),which is known to lead to rapid inter granular attack only in certain nitric acid environments. It does not detect susceptibility to end grain attack, which is also found only in certain nitric acid environments. The ferric sulfate-sulfuric acid test does reveal susceptibility associated with a sigma-like phase constituent in stabilized stainless steels, AISI 321 and 347, and in cast chromium-nickel-molybdenum stainless steels (CF-8M, CF-3M, C6-8M, and CG-3M). 
 
Practice C—Nitric Acid Test is a 240-h test in boiling, 65% nitric acid that detects susceptibility to rapid intergranular attack associated with chromium carbide precipitate and with sigma-like phase precipitate. The latter may be formed in molybdenum-bearing and in stabilized grades of austenitic stainless steels and may or may not be visible in the micro-structure. This test also reveals susceptibility to end grain attack in all grades of stainless steels. 
 
Practice E—Copper–Copper Sulfate–16% Sulfuric Acid Test Is a 24-h test in a boiling solution containing 16% sulfuric acid and 6% copper sulfate with the test specimen embedded in metallic copper shot or grindings, which detects susceptibility to intergranular attack associated with the precipitation of chromium-rich carbides. It does not detect susceptibility to intergranular attack associated with sigma phase or end-grain corrosion, both of which have been observed to date only in certain nitric acid environments. 
 
PracticeF—Copper–CopperSulfate–50% Sulfuric Acid Test is a 120-h test in a boiling solution that contains 50% sulfuric acid, copper sulfate, and metallic copper and that detects susceptibility to intergranular attack associated with the precipitation of chromium-rich carbides. It does not detect susceptibility to attack associated with sigma phase
 
Wish this introduction can help you to know IGC (Corrosion Test) well.

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