ABSTRACT It is common practice to perform intergranular corrosion testing in accordance with ASTM (1) G28 on solid solution nickel alloys, e.g. UNS N . Alloy 22 is a Ni-Cr-Mo alloy (Nickel-Chromium-Molybdenum) and is one of the most versatile corrosion resistant alloys used in industry today. Intergranular Attack Susceptibility For Nickel Alloys.

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Problems with corrosion test ASTM G28 – General Corrosion Topics

Good material should have a corrosion rate substantially less than the threshold value. Why were these tests designed? Rock Mechanics Symposium and 5th U. ASTM G28 was designed for nickel-based alloys, and a list of applicable alloys for methods A and B is in the standard. Just remember that these tests were devised for specific groups of alloys and should not be applied to all CRAs!

ISO is specifically for duplex and all austenitic stainless steels, and recommends ageing at two different temperatures:.

ASTM A was designed for austenitic stainless steels, specifically the series alloys. Page 1 of 1. This test should be avoided for most CRAs, except in the circumstances described below, in section 4. This document describes all three of these tests for four common standards, and describes the differences. In the case of qstm, chromium-bearing alloys, the test method may be applied to wrought and weldments of products.

These environments are sstm oxidizing and acidic e. ISO is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows: The problem is that the sample was destroyed just six hours, including the test that is annealed solution. However, there are necessarily limitations in the potential applicability of standard tests because the mechanism of corrosion in the service environment may be different than that targeted in the standard test, due to the difference between the actual service environment and the test solution.


Satm of an international conference Diverless and Deepwater Techology: The most convenient size is often a cylinder 10mm diameter by mm long, but other dimensions are possible to suit particular product forms. Therefore, the presence of grain boundary precipitation can be elucidated 2g8 the occurrence of intergranular corrosion in the test environments. Some standards require the test sample to be aged prior to testing, to simulate the precipitation that might occur during welding.

None of these are identical and g8 substitution of results is not possible. Advanced search Show search help. V28 is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows:.

The test methods in Table 1 were designed with specific alloys in mind, but the proliferation of new CRAs has meant that the selection of a suitable test method is difficult.

Someone would have experience in this matter. It does not say what to do about duplex or super austenitic alloys. There are a number of recognised tests when it comes to the intergranular corrosion testing of corrosion resistant alloys CRA. As 15 hours is a difficult test period in practice, and is only a minimum, conducting the test for 20 hours overnight means that the two tests are equivalent.

Hello everybody, My query is as follows: When a test g228 been selected, follow the detailed directions aetm that standard for making up the test solution, the preparation of test samples and the finish to be used.


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It has been used for the duplex stainless steel UNS Swhich has been used for nitric acid cooler tubes. About us Contact us Help Terms of use.

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The uniform corrosion rate obtained by this test method, which is a function of minor variations in alloy composition, may easily mask the intergranular corrosion components of the overall corrosion rate on alloys N, N, N, and N Log in to your subscription Username. For alloys not listed in this standard, it will be necessary to carry out some tests on material in various conditions to determine the threshold.

The exception to this is ASTM G28 method A, where rates for the onset of intergranular corrosion are described in asmt 1.

Where no specific test is specified, Table 5 suggests the most appropriate alongside a second choice, if the first is declined. The precipitation of such chromium-rich or molybdenum-rich particles often carbides usually also leads to regions depleted of Cr or Mo surrounding the precipitates. SEP method 3 is a special environment only suitable for the Ni-Mo alloys, as described below, in section 4.