Abstract. A detailed study of AISI and stainless steels (SSs) has been conducted to correlate the degree of sensitization (DOS) measured by the. ASTM a Test, Intergranular Corrosion, IGC, ASTM A Practice, Copper – Copper Sulfate – 16% sulfuric acid, ASTM A – Practice E (Strauss Test). ASTM A Practice E test. This practice describes the procedure by which the copper-copper sulfate% sulfuric acid test is conducted to determine .
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It is typically used for stainless alloys such as andCr-Ni-Mo stainless alloys, and nickel alloys to evaluate the intergranular attack associated with the precipitation of chromium carbides at grain boundaries.
Sample condition before soaking in Ferric chloride solution.
Classification of the structure after A Practice A analysis will determine if the material is acceptable or if additional testing is required. 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.
Corrosion is measured by a weight loss that is converted to a corrosion rate. 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.
ASTM A is a common intergranular corrosion testing method that can quickly screen batches of material to determine corrosion susceptibility. 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. The samples are weighed at each interval to determine mass loss and degree of susceptibility to intergranular attack. Corrosion Tests are conducted to determine the resistance of a metal to chemical attack.
The bent samples are examined at low magnification, where the appearance of cracks or fissures indicate intergranular attack. All five methods within this specification involve exposing specimens to a chemical mixture designed to encourage corrosive behavior. Our knowledgeable scientists have the experience and expertise necessary to determine the most appropriate intergranular attack testing methods for your material while providing actionable results you can rely on.
ASTM A Intergranular Corrosion Testing and Analysis
Edges shall be rounded and a fine final polish is required at all surface exclude the weld cap and root area.
The ASTM A tests can determine if the proper heat treatment was performed or if the alloys are in danger of intergranular corrosion occurring in use. The Oxalic Practide test is only used to ensure that no corrosion exists; samples are labeled either “Acceptable” or “Suspect”. The etch structure types used to classify the specimens are: Specimen surface before soaking in boiling W Sulfate-Sulfuric Acid solution. Choosing the correct method s rely on a complete understanding of your material and processes, praactice well as the concept of corrosion itself.
The Strauss test is commonly used to evaluate the heat-treatment of as-received material, the effectiveness of alloying additions of elements such as Nb and Ti, or the effectiveness of reducing carbon content to resist intergranular attack. Work Item s – proposed revisions of this standard.
In SEM analysis, intergranular corrosion is clear by the dark lines where the grain boundaries are eaten away. It depends on which Practice is selected, but typically ranges from to days for different tests. Some specific hazards statements are given in Practice A, the oxalic acid etch test is used as a rapid technique to screen samples of certain stainless steel grades to ensure they are not susceptible to intergranular attack sensitization. View more articles about Aerospace Oil and Gas Transportation.
The chart below comes from the ASTM A standard for selection of the appropriate test by alloy type:. If you are not sure, please contact us for assistance. After exposure in the boiling solution, the specimen is bent. Based on your materials, application, and requirements, the other 4 methods provide specific focuses. The oxalic acid test is commonly used before the Strauss test to determine if a sample is susceptible; samples that pass method A will generally show low corrosion rates in the Strauss test.
What is your typical turnaround time? Contact us now for pricing or a quote! It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Sensitization causes the grain boundaries of a material to precipitate, creating carbide deposits and causing the material to be susceptible to intergranular attack.
These tests do not provide a basis for predicting resistance to forms of corrosion other than intergranular, such as general corrosion, pitting, or stress-corrosion cracking. How do you select the right ASTM corrosion testing method for your material?
For example, in highly oxidizing solutions, intergranular attack can occur due to intermetallic phases, while attack of carbides may occur somewhat less oxidizing solutions. Metals like stainless steels and aluminum contain elements such as niobium and chromium, often integrated because of their natural corrosion resistance.
It is not sensitive to size or orientation, provided that edge attack is not ignored. The inch-pound equivalents are in parentheses and may be approximate. Practice E, the Strauss test, is performed to assess attack associated with chromium-rich carbide formation; it does not detect susceptibility to sigma phase formation.
Our laboratory is well organized, adequately equipped, and have competent staff who are trained to conduct these tests. Methods for preparing the test specimens, rapid screening tests, apparatus setup and testing procedures, and calculations and report contents are described for each testing practice. The test uses a visual inspection of the surface of the bent specimen to determine pass or fail. The Huey test works well to analyze chromium depleted regions and intermetallic precipitates, such as sigma phase, and is also used for materials in strongly oxidizing environments such as nitric acid.
Test sample was etched using Oxalic Acid with electrolyte etching. ASTM A testing is a popular method of choice due to the variety of practices available and the relatively short turnaround for results.