Nitric Acid, ASTM A, Practice C, (Huey Test) The specimens are boiled for five periods, each of 48 hours, in a 65 per cent solution of nitric acid. The corrosion. employed to measure the relative susceptibility of austenitic stainless steels to intergranular attack. ASTM A Practice C, boiling nitric acid test is also known . Ferric Sulfate – Sulfuric Acid, ASTM A – Practice B (Stretcher Test). Ferric Sulfate Nitric Acid, ASTM A, Practice C, (Huey Test). Nitric Acid, ASTM A
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To understand intergranular corrosion testing or intergranular attack commonly abbreviated as IGC or IGAit is important to understand what causes the process to occur.
Intergranular Corrosion Testing: An Overview of ASTM A262
Metals like stainless steels and aluminum contain elements such as niobium and chromium, often integrated because of their natural corrosion resistance.
However, when a material is exposed to high temperatures for long periods of time, a process called sensitization may occur. Sensitization causes the grain boundaries of a material to precipitate, creating carbide deposits and causing the material to be susceptible to intergranular attack. Since high temperature processing praactice as heat treatment is a common practice, many manufacturers wish to perform intergranular corrosion qualification testing on each batch, to ensure that the material has been processed correctly and does not show signs of corrosion susceptibility.
ASTM A testing is a popular method of choice due to the variety of practices available and the relatively short turnaround for results.
All five methods within this specification involve exposing specimens to a chemical mixture designed to encourage corrosive behavior. At the conclusion off the test, specimens are either visually examined or measured for weight loss and compared to an established corrosion rate for that specific material type.
This simple etching technique is used as a quick screening method to ensure that a material is free of intergranular corrosion susceptibility. The Oxalic Acid test is only used to ensure that no corrosion exists; samples are labeled either “Acceptable” or “Suspect”. A different ASTM A test method must be used to quantify the level of corrosion or to disqualify a material for use. The Oxalic Acid test is also only applicable to corrosion associated with chromium carbide precipitates and is only useful for specific material grades.
Please refer to the specification for more details. The level of corrosion is determined by mass loss.
Similar to the Streicher test, the Huey test method uses a nitric acid solution and subjects the specimen to five hour boiling intervals. The samples are weighed at each interval to determine mass loss and degree of susceptibility to intergranular attack.
This method is preferable for practiec depletions and corrosion in intermetallic phases. This test is used exclusively to determine corrosion in areas high in chromium carbide formations, and is not as effective for intergranular attack caused by other means.
Strauss test specimens are boiled in a F Sulfate – Sulfuric Acid mixture for 15 hours. A bend test followed by a visual or micro-examination are used to determine “Pass” or “Fail” of test specimens.
ASTM A Testing: An Overview of Intergranular Corrosion | Element
This method is a hour boiling test for “as received” specimens of stainless steel. The Copper Sulfate Test is especially effective for determining susceptibility to intergranular attack for low carbon steels.
Our knowledgeable scientists have the experience and expertise necessary to determine the most appropriate pracice attack testing methods for your material while providing actionable results you can rely on.
View more articles about Aerospace Oil and Gas Transportation. We provide intergranular corrosion evaluation, salt spray testing, stress corrosion, and various other methods to simulate exposure aatm your products or materials to corrosive environments.
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Discover perspectives, resources, and advice from our world-leading Engaged Experts. Choosing an Intergranular Corrosion Test Method Since high temperature processing such as heat treatment is a common practice, many manufacturers wish to perform intergranular corrosion qualification testing on each batch, to ensure that the material has been processed correctly and does not show signs of corrosion susceptibility.