Abstract
Stainless steel AISI 304L, because of its satisfactory corrosion resistance, is widely used as a construction material for nitric acid service, particularly for nuclear fuel reprocessing plants. However, the presence of active inclusions (observed as end grain pitting II) makes the material susceptible to attack in nitric acid environments. This paper highlights the severity of such attack during exposure to 65% boiling nitric acid (as per ASTM A 262 practice C). It is seen that the corrosion rates are quite high: The attack initiates at the inclusion sites (transverse section) which are in contact with the acid and is intergranular in nature. I tis also seen that the inclusions do not affect the results of tests in other environments (e.g. ASTM practices B and E). Electrochemical potentiokinetic reactivation tests were carried out to observe the response in the presence of active inclusions. The test was found to be sensitive to the inclusions, which was reflected in higher Pa values at the transverse sections. An attempt has been made to explain the influence of these types of inclusions in the material on the observed enhanced rates of intergranular corrosion.
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