Evaluation of the corrosion behavior of laser powder bed fusion (L-PBF) stainless steel 316 L in a simulated synovial fluid under inflammatory conditions

Abstract

This study investigates the corrosion behavior of a stainless steel 316 L (SS316L) manufactured using laser powder bed fusion (L-PBF) that can potentially be used in total joint replacements. To simulate in vivo conditions after a joint replacement, a modified simulated synovial fluid (i-SSF) was used while a 0.1 M HCl solution was used to evaluate localized corrosion characteristics in local acidic conditions. Cyclic potentiodynamic polarization (CPP) was employed to analyze corrosion kinetics and localized corrosion resistance, while electrochemical impedance spectroscopy (EIS) was used to monitor film formation in the test solutions. From both the CPP and EIS results, the L-PBF SS316L was found to form a more protective passive film that showed lower susceptibility to breakdown characterized by an E_pit of about twice that of a wrought SS316L in the i-SSF solution. The corrosion resistance in 0.1 M HCl was slightly reduced in the L-PBF SS316L but the presence of passive film that was more resistant to breakdown was observed. Due to the complex interactions between the various components present in the i-SSF, the surfaces after CPP showed a wider, shallower attack morphology while that in 0.1 M HCl showed a more localized attack with small pits randomly covering the surface. Laser scan track boundaries and cell interiors were found to preferential regions of attack.