Articles - Kinds of corrosion in stainless steel: crevice corrosion

In this article crevice corrosion in stainless steels is briefly analyzed.

Despite its excellent properties against corrosion, deterioration due to reaction against the environment can also appear in stainless steel, with a higher or lower influence depending on the grade and the emplacement of the material.

As seen in some precedent article about pitting corrosion, at a general level there are two main kinds of corrosion, the uniform and the localized one.

Crevice corrosion would be in the second category, appearing in specific parts of the material (crevices) which, when submerged into a dissolution, contains an isolated portion of it. This fact generates a different concentration of oxygen between both parts, producing therefore galvanic corrosion.

The presence of chloride contributes to this kind of corrosion, as its concentration destroys the passive oxide layer. Once this point reached it is only a matter of time that the destroyed layer is expanded to the base of the metal, being even able to cause corrosion in all the material.

Similarly to PREN value analyzed months back (Pitting Resistance Equivalent Number), crevice corrosion also has an indicator for its measurement, called CCCT (Critical Crevice Corrosion Temperature).

However, in despite of being able to be used to compare different steels depending on its resistance to crevice corrosion, it is worth bearing in mind that it is not a constant like PREN, being thus a must to take an experimental measurement to determine it for each material.



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