Susceptibility to Localized Corrosion of ASTM F745 and UNS S32750 Stainless Steels Influence of pH and Cytotoxicity Evaluation

GREGORUTTI, RICARDO W.; PARISI, JULIETA; GREGORUTTI, RICARDO W.; PARISI, JULIETA; GRAU, JORGE E.; REIGOSA, MIGUEL; GRAU, JORGE E.; REIGOSA, MIGUEL; CASTROGIOVANNI, DANIEL; ELSNER, CECILIA I.; CASTROGIOVANNI, DANIEL; ELSNER, CECILIA I.

Innovations in Corrosion and Materials Science (Formerly Recent Patents on Corrosion Science)

Bentham Science Publishers

Año: 2020 vol. 10 p. 47 - 57

2352-0949

Abstract: Background: Body fluids are highly corrosive as they contain chlorides and hydroxidesions, as well as salts, bacteria, proteins and dissolved oxygen. The pH of the body is usually around7.4, although this value can vary in a range of 4 to 9 after surgery or because of haematomas, inflammationsand infections. ASTM F745 (type 316L) stainless steel has been used for load bearing partialand total joint replacements and post trauma reconstructive surgeries. However, long exposure to theaggressive effect of chloride ion present in the human body, may increase the susceptibility to sufferlocalized corrosion. Although UNS S32750 has greater corrosion resistance to chloride ion, its magneticcharacteristics inhibit its use in implantable devices. Nevertheless, this stainless steel could be usedin temporary implants and orthodontic appliances such as brackets, wire arches and bands, due to its highresistance to corrosion, the greater mechanical resistance and the high capacity of plastic forming.Objectives: The objective was to evaluate the susceptibility to localized corrosion in simulated bodyfluid, in the pH range of 4 to 9. Another objective was to evaluate the cytotoxicity of Cr and Ni presentin the chemical composition of both stainless steels. Cytocompatibility was also analysed byseeding cells on the surfaces of both stainless steels.Methods: Cyclic polariation test was performed to evaluate the susceptibility to localized corrosion in0.9 wt% NaCl aqueous solution, at pH between 4 and 9, maintained at 37°C. For cytotoxicity evaluation,neutral red, MTT and collagen assays were performed using UMR-106 cell line. Cytocompatibilitywas analysed by seeding UMR-106 cells on the surfaces of both stainless steels.Results: F745-SS was more susceptible to suffer localized corrosion than UNS S32750. Although itshowed a tendency to develop transpassive reactions at low pH, galvanostatic tests did not reveal theonset of localized corrosion. The results from the cytotoxicity assays indicated that no adverse effectswere observed. UMR-106 osteoblastic cells showed high viability, however, a slight reduction in thecollagen production was observed. The cytocompatibility was also satisfactory, since the cells seededon the surfaces had adequate proliferation.Conclusion: F745-SS is more susceptible to suffer localized corrosion than UNS S32750 in the pHrange between 4 and 9. UNS S32750 showed an extensive passive region, however, transpassive reactionswere observed at lower pH. On the other hand, no cytotoxic effects were promoted by both stainlesssteels, although a slight reduction in collagen production was observed. Cells seeded on F745-SS andUNS S32750 surfaces had an acceptable proliferation, without evidence of changes in their morphology.