When using stainless and duplex steels, ASTM G48 is widely used to ensure the quality of the material and resistance to pitting and crevice corrosion. ASTM G 48 is a relatively severe test, but lack of definition in the standard can lead to variation of data. We follow a standard practice we have developed to minimize these variations and provide consistent data. However, the G48 test is meant for ranking or qualification, and not as designed for determining a corrosion rate over time.
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When using stainless and duplex steels, ASTM G48 is widely used to ensure the quality of the material and resistance to pitting and crevice corrosion. ASTM G 48 is a relatively severe test, but lack of definition in the standard can lead to variation of data.
We follow a standard practice we have developed to minimize these variations and provide consistent data. However, the G48 test is meant for ranking or qualification, and not as designed for determining a corrosion rate over time. There are 6 Methods: A and B are for qualification of alloys to pitting and crevice corrosion at specific temperatures, C and D are for determining the critical pitting and crevice corrosion temperatures of chromium and nickel alloys, and E and F are for stainless alloys.
Which one do you need? The answer is: it depends. There are several factors that can influence the selection of methods; we can help you with this part of the process as well. The available pitting and crevice testing methods include:. Method B — Ferric chloride crevice test. Method C — Critical pitting temperature test for nickel-base and chromium-bearing alloys.
Method D — Critical crevice temperature test for nickel-base and chromium-bearing alloys. Method E — Critical pitting temperature test for stainless steels. Method F — Critical crevice temperature test for stainless steels. Our lab offers all 6 methods of this test as well as ASTM G, the electrochemical method for similar analysis. In many ways, G is ideal for use instead of methods C-F as it is a more rapid method that can be performed within days instead of weeks.
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G48 contains six different test methods for evaluating the pitting and crevice corrosion resistance of stainless and nickel alloys. These are:. However, these parameters can be modified to suit individual test needs. Note that these are not acceptance tests as written in G48 as there are no acceptance criteria. They can be used as acceptance tests if criteria e. Methods C through F are designed as incremental tests and require multiple specimens. These tests identify the minimum critical temperature needed to initiate pitting or crevice corrosion.
Pitting and Crevice Corrosion Testing
This paper will provide a brief overview of the standard and highlight several important points that can be sources of error or misunderstanding. Results will be presented on variability of crevice corrosion testing from rubber band type, crevice former geometry, and surface roughness. This is a simple immersion test where the test sample is placed in a temperature-controlled solution of FeCl 3. The FeCl 3 solution provides an aggressive environment to promote localized corrosion due to the presence of chloride ions, oxidizing conditions, and low pH.
Historical Version s - view previous versions of standard. More G The results may be used for ranking alloys in order of increasing resistance to pitting and crevice corrosion initiation under the specific conditions of these methods. Methods A and B are designed to cause the breakdown of Type at room temperature. No statement can be made about resistance of alloys in environments that do not contain chlorides. Consequently, the degree of corrosion damage that occurs during testing will generally be greater than that in natural environments in any similar time period. Therefore, grinding and pickling of the specimen will mean that the results may not be representative of the conditions of the actual piece from which the sample was taken.