DETECTING INTERGRANULAR ATTACK ON STEELS
Intergranular corrosion refers to material degradation that occurs along the grain boundaries of metallic materials after exposure to a corrosive environment. It is a type of corrosion where the grain boundaries of crystallites in austenitic steel are more susceptible to corrosion than the inside of the material. Grain boundaries can become depleted during the manufacturing of stainless steel round bars, the hot forging of heads on bolts, or the hot bending of anchor bolts, U-bolts, or eye bolts.
Our expert testing team can detect intergranular corrosion testing using below stated methods.
- The Oxalic Acid Test
- The Strauss Test
- The Huey Test
- The Streicher Test
- The Copper Sulfate Test
ASTM A262 – A
PTS performs a rapid screening test conforming to ASTM A262 A, which involves the etching of austenitic steels in a 10% wt oxalic acid solution, which allows quick identification of susceptible steel grades to intergranular attacks associated with chromium carbide precipitations to improper heat treatment. The etch test result will enable interpretation of whether the material is acceptable for use or will need to be subjected to additional hot acid tests in ASTM 262.
ASTM A262 was designed for austenitic steels (specifically the 300 series). Hence, only specific steel grades listed in ASTM 262 are qualified for the rapid screening tests and are listed below: AISI 304, 304L, 316, 316L, 316H, 317, 317L, CF-3, CF-9, CF-3M, CF-8M.
ASTM A262 – B (Streicher Test)
PTS performs hot acid corrosion test conforming to ASTM A262 B, which involves the submersion of the sample in boiling ferric sulphate– sulfuric acid for a 120-hrs duration and evaluating the material through quantitative weight loss analysis.
This test is normally used to assess stainless alloys with Cr>20.0% and Mo>3.0% composition, such as AISI 321, 347, to evaluate the precipitation of chromium carbides at grain boundaries.
Another test variation, ASTM G28-A, is also available specifically for nickel-based alloys.
ASTM G28 – A
PTS performs hot acid corrosion test conforming to ASTM G48A, which involves the submersion of the sample in boiling ferric sulphate – sulfuric acid for a 120-hrs duration and evaluating the material through quantitative weight loss analysis.
This test is normally used to access nickel-based alloys such as N06007, N06022, N06030, N06059, N06200, N06455, N06600, N066625, N06686, N06985, N08020, N08367, N08800, N10276 evaluate the precipitation of chromium carbides at grain boundaries in similar environments.
ASTM A262 – C (Huey Test)
PTS performs hot acid corrosion test conforming to ASTM A262 C, which involves the submersion of the sample in boiling nitric acid solution for five intervals of 48-hrs duration and evaluating the material through quantitative weight loss analysis.
This test is normally used to assess austenitic stainless steels for the presence of chromium-depleted regions and detrimental intermetallic precipitates (I.e., Sigma phases). Materials commonly tested are stainless steels containing Cr>17.0% and Mo>3.0% composition.
Products designed for highly oxidizing solutions, such as oil wells and manufacturing industries, are commonly evaluated using A262 C.
ASTM A262 – E (Strauss Test)
PTS performs hot acid corrosion test conforming to ASTM A262 E, which involves the submersion of the sample in boiling copper sulphate – sulphuric acid solution for a 24-hrs duration and evaluating the material through visual examination after bent testing.
This test is normally used to assess intergranular attacks associated with chromium-rich carbide formation in austenitic stainless steels.
APPLICATION OF INTERGRANULAR CORROSION TEST:
Reveal errors of batches that are incorrectly processed
To determine corrosion in areas high in chromium carbide formations
Common Test Methods
ASTM A262
ASTM G28
ISO 3651
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Our corrosive analysis lab is equipped with state-of-the-art testing equipment to gather valuable insight into the causes of corrosion. Our expert testing team at Professional Testing Services can detect the cause of the corrosion with an intergranular corrosion test.
For more information on intergranular corrosion tests, call us or send us an enquiry today.
