Investigation of general corrosion of austenitic stainless steel types 304 L and 317 L, especially from the aspect of their chemical composition

Abstract

Austenitic stainless steels are among the most widely used types of stainless steel. The most commonly used grades are the American Iron and Steel Institute (AISI) 300 series of alloys. Starting from the basic 304 alloy (Fe-19Cr-10Ni), molybdenum is added to improve resistance to pitting (2-3 wt.% in the case of type 316 and 3-4 wt.% in type 317). Sensitisation due to chrome depletion during welding and other heat treatments, and the possible resultant intergranular corrosion, can be avoided through the use of low-carbon grades (304L, 316L, 317L, in which carbon is limited to 0.03 wt.% max.) or by adding titanium (type 321) or niobium and tantalum (type 347) to precipitate carbon at higher temperatures. The addition of chrome also imparts greater oxidation resistance, whilst nickel improves the ductility and workability of the material at room temperature.

In this paper, general corrosion of austenitic stainless steels, specifically low-carbon types 317 L and 304 L, was investigated. The research results are presented in the form of Tafel polarization curves, expressed through corrosion current density and open circuit potential. The results prove that the rate of general corrosion of the tested austenitic stainless steels decreases by lowering the temperature of the HCl solution, decreasing the concentration of HCl, and the presence of molybdenum in the composition of steel type 317 L.