There are a number of recognised tests when it comes to the intergranular corrosion testing of corrosion resistant alloys CRA. This document describes all three of these tests for four common standards, and describes the differences. Just remember that these tests were devised for specific groups of alloys and should not be applied to all CRAs! This document also points out which alloys the tests are intended for, and recommends the most appropriate test when none is specified. Intergranular corrosion tests are primarily designed to detect carbide precipitates on grain boundaries.
|Published (Last):||27 August 2007|
|PDF File Size:||7.15 Mb|
|ePub File Size:||10.88 Mb|
|Price:||Free* [*Free Regsitration Required]|
Historical Version s - view previous versions of standard. Work Item s - proposed revisions of this standard. More A This specification covers the standard practices for detecting susceptibility to intergranular attack in austenitic stainless steels.
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 etch structure types used to classify the specimens are: step structure, dual structure, ditch structure, isolated ferrite, interdendritic ditches, end-grain pitting I, and end-grain pitting II.
This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application.
ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date. 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. The inch-pound equivalents are in parentheses and may be approximate. 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.
Some specific hazards statements are given in Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Scope 1. Link to Active This link will always route to the current Active version of the standard.
ASTM A262 Intergranular Corrosion Test IGC
Intergranular Corrosion Testing: An Overview of ASTM A262
Intergranular corrosion occurs as a result of precipitation of nitrides , carbides , and other intermetallic phases , such as sigma phase, that occurs along the grain boundaries. If materials with incorrect heat treatment enter service, they are liable to crack or fail by intergranular corrosion IGC much more rapidly than properly treated materials; ASTM A is a screening test to help find batches that are incorrectly processed. Intergranular corrosion shows up as the dark black lines around the grain boundaries. How do you select the right ASTM corrosion testing method for your material? The first and fastest step is the ASTM A Practice A, a rapid same-day screening method in Oxalic acid to determine the susceptibility to intergranular corrosion.
In the presence of tensile stress, cracking may occur along grain boundaries and this type of corrosion is frequently called "interranular stress corrosion cracking IGSCC " or simply "intergranular corrosion cracking". Intergranular corrosion in stainless steel may result from precipitation of carbides, nitrides or intermetallic phases. Only in the most highly oxidizing solutions can intergranular attack be caused by intermetallic phases. When a test is to be restricted to carbides, in a material containing nitrides or intermetallic phases, a less oxidizing solution is chosen. Oxalic Acid Test, ASTM A, Practice A Oxalic Acid Etch The oxalic acid etch test is a rapid method of screening those specimens of certain stainless steel grades which are essentially free of susceptibility to intergranular attack associated with chromium carbide participates. The test is used for acceptance but not rejection of material.