Regarding the issue of intergranular corrosion
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Intergranular corrosion is a condition that often arises in the design of chemical process pipelines, but there has been no high clarity on this issue! When referring to neck corrosion in the materials documentation, the chromium-deficiency theory is the most commonly used; in addition, some media that can easily cause intergranular corrosion in materials are briefly mentioned. However, I feel that the so-called chromium-deficiency theory focuses more on the material itself or the processing techniques, without specifically indicating what concentration of what medium can cause intergranular corrosion I was wondering if anyone could explain to me when intergranular corrosion needs to be taken into consideration when selecting materials, and how to define the medium. Thank you! ~
Intergranular corrosion shouldn’t be closely related to the medium, right? Intergranular corrosion refers to the phenomenon in austenitic stainless steels and austenitic-ferritic stainless steels, where carbon precipitates at temperatures between 400°C and 850°C, resulting in chromium-deficient areas. When the chromium content drops below 12%, the material loses its corrosion resistance. Since stainless steels are used in environments that are inherently corrosive, the chromium-deficient areas near the grain boundaries lose their corrosion resistance, leading to intergranular corrosion
Search online for “Harm and Cause Analysis of Intergranular Corrosion”; it provides more information on the topic. Downloading that thing requires points or currency; it’s not possible to upload it, so one can only view it on their own. .
Generally, stainless steel possesses corrosion-resistant properties because the chromium element present in it combines with oxygen to form chromium oxide, which coats the metal surface and acts as a protective layer against corrosion. Intergranular corrosion occurs when, in austenitic stainless steel, chromium carbide is deposited between the crystals at certain temperatures; since the bonding force between carbon atoms is stronger than that between carbon and oxygen, the metal loses its corrosion resistance.