The corrosion behavior of compositional modified AISI type 304L stainless steel for nitric acid application

High corrosion resistance in different concentrations of nitric acid is essential for structural steels to be used for the aqueous reprocessing of spent nuclear fuels with high plutonium content.

In the present study, the corrosion resistance of type 304L stainless steel (SS) with modified composition was evaluated in different concentrations of nitric acid using surface analytical techniques, weight loss method and electrochemical measurements.

Weight loss measurement in boiling 65 per cent nitric acid showed a low corrosion rate value of about 0.2 mm/y (8 mpy) after 240 h exposure. Electrochemical measurements revealed the shift in open circuit potentials as well as corrosion potential toward more noble direction, and the results of electrochemical impedance spectroscopy studies indicated the reduction in the thickness and stability of the passive film with increasing concentration from 6 to 11.5 M nitric acid.

The low corrosion rate observed for this steel is attributed to the higher content of Cr (19 per cent), Ni (10 per cent) and Si (0.3 per cent) and controlled minor alloying elements (S, P, B, C, etc.) in the alloy that contributed to improving the transpassive corrosion resistance and minimizing the intergranular corrosion attack. The X-ray photoelectron spectroscopic analysis revealed the composition of the passive films to be mainly of iron and chromium oxides.

Materials with lower corrosion rates are desirable for applications in nitric acid.

The used of nitric acid creates a severe corrosive environment in chemical or aqueous nuclear reprocessing plants, and hence with a modified composition of type 304L SS resulting in minimizing failure of components are desirable for reducing cost and maintenance.

The present paper is an original work carried out by the authors on the corrosion resistance behaviors of composition modified AISI type 304L SS for nitric acid application. The effects of different nitric acid concentrations were compared to provide understanding on in applicability in boiling and high nitric acid concentrations.