IGC Testing for Stainless steel plates

http://www.tcreng.com/services/corrosion-IGC-tests.shtml

Ask this Company in India--they will advise where it is needed.

IGC stands for Inter Granular Corrosion. IGC test is required for Stainless Steel to check the Inter Granular Corrosion Resistance and this test is applicable for all SS Pipes, Forgings.

At atmospheric conditions, the chances of IGC are almost neglegible but at elevated temperature the probability is high. If we heat the sample above 500 to 800 degree centigrade and then allow aging for long period of time then there are chances of formation of chromium depleted zones. So, to check the applicability of SS at elevated temperature and for longer period of time, IGC test should be carried out.

Tehseen

Hi all,

As said before, IGC means Inter-Granular Corrosion.

This is one of the types of corrosion which may occur in some Austenitic stainless steels. (Most people forget that there are more types of SS, i.e: ferritic, martensitic, precipitation hardened, etc. and some of them are not resistant to IGC)

IGC occurs as its name indicated trough the grain boundaries because of complex chromium carbides in that location. That makes diminish the chromium content available to form the protective chromium oxide layer which is the origin of the type of steels (Usually are considered "stainless" if they have about 12% Cr minimum).

The IGC phenomenon is related to the chemical composition, heat history and environment and not to the product form (plate, tube, casting or forging)

Austenitic stainless steels are usually according to most standards supplied in the solution annealed condition, that is austenitized to a temperature in which all possible chromium carbides are dissolved and then quenched to frozen the equilibrium reached at this high temperature, avoiding the new formation of more carbides.

If such steels are subject to temperatures in the range of 500 - 900ºC chromium carbides can precipitate in the grain boundaries resulting in which is known as "sensitization". This can occur for example in the heat affected zone of weldings.

To avoid "sensitization" two types of austenitic SS were developed: L grades (low carbon, %C< 0.03) and "stabilized grades" (with some small contents of Ti or Nb which form carbides easily than chromium). It's quite simple: to avoid the formation of enough chromium carbides as to lower the Cr content in the grain boundaries to less than 12%, you can lower the C% or include some elements more avid for C than Cr is)

The performance or not of IGC test depends on the specific requirement of the specified standard and/or the specific User/Client requirements. Most standards include this type of test as a "supplementary requirement" so you must test it only if specifically requires in the order.

Methods for perform that testing can be found in ASTM Standard A262 or in EuroNorm 114