Corrosion properties of a low-nickel austenitic porous stainless steel in simulated body fluids

Abstract

Nickel can cause severe allergic reactions. Therefore, efforts are made to reduce the content of nickel in austenitic stainless steels (SS). Powder metallurgy (PM) techniques can produce this steel in a highly affordable way. A novel low-nickel high-nitrogen austenitic powder metallurgy PM stainless steel is investigated in terms of corrosion behavior. Nitrogen, because of its gammagenic effect, is the applied sintering atmosphere. Two sintering processes are applied by controlling the sinter-cooling rate (furnace- and water-cooling). This material shows an austenitic microstructure free of precipitates only after the water-cooling process. The electrochemical behavior in two simulated body fluids—phosphate buffered saline (PBS) solution and Ringer solution—are studied. Corrosion behavior is evaluated by means of anodic polarization measurements and cyclic polarization curves. In addition, Electrochemical Impedance Spectroscopy is used to evaluate the corrosion resistance of this steel in PBS at open circuit potential and at 100 mV above corrosion potential. The water-cooling process promotes better corrosion behavior in simulated body fluids for high nitrogen and low nickel than a conventional (high nickel) austenitic PM SS 316LN type.