Corrosion behaviour and biocompatibility of a novel Ni-free intermetallic coating growth on austenitic steel by hot dipping in an Al–12.6%Si alloy M. A. Arenas • E. Frutos • L. Saldan ˜a • A. Conde • L. Labajos-Broncano • M. L. Gonza ´lez-Martı ´n • J. L. Gonza ´lez-Carrasco • N. Vilaboa Received: 5 November 2010 / Accepted: 7 March 2011 / Published online: 25 March 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Commercial 316 LVM austenitic stainless steel samples have been coated by immersion in a bath of molten Al–12.6%Si alloy for 120 s. The coating consists of the Al 12 (Fe,Cr) 3 Si 2 intermetallic. In vitro corrosion behaviour has been evaluated in the Ringer’s solution by means of potentiodynamic curves and electrochemical impedance spectroscopy. The results reveal that the coated specimens exhibit lower susceptibility to localised corrosion with respect to the substrate. XPS analysis suggests that the ennoblement of the pitting potential is due to the formation of a chromium oxyhydroxide containing passive layer. The intermetallic coating shows a good biocompatibility, as demonstrated by culturing human mesenchymal stem cells isolated from bone marrow which attached, grew and dif- ferentiated to the osteoblastic lineage to a similar extent on coated and bare steels. In summary, this study proposes a method that generates Ni-free coatings of the stainless steel with useful properties for biomedical applications. 1 Introduction The 316 Low Vacuum Melting (LVM) austenitic stainless steel is a low-cost metallic biomaterial with an easy mech- anization and reasonably good biocompatibility [1, 2], widely used in the fabrication of orthopaedic devices such as bone plates, bone screws, pins, and rods. Despite its satis- factory in vitro corrosion resistance, under frictional con- ditions or in the presence of an aggressive medium ion release may lead to clinical complications. Metal hyper- sensitivity reactions are currently estimated to affect \ 1% of the patients with implants [3]. Ni is the most common sen- sitizer metal in humans, followed by Co and Cr [4, 5]. These features have triggered great activity among researchers towards the development of Ni-free steels with a large amount of nitrogen (up to 4.2 at.%) and manganese (up to 23 at.%) [6–8] or oxide dispersion strengthened (ODS) alloys [9–11]. Satisfactory results can be also obtained by the development of coatings or surface modifications. Unfor- tunately, most of the methods developed for Ti and their alloys are not always applicable to the steel [12]. This study deals with 316 LVM steel coated by hot dipping in an Al–Si alloy, i.e. siliconisation, which is a low-cost technique successfully used to increase the Si content at the surface without detrimental effects on the mechanical properties of the bulk. Siliconisation of 316 LVM coats the steel with a dense Al 12 (Fe,Cr) 3 Si 2 inter- metallic coating well adhered to the substrate [13]. This coating has successfully enhanced the magnetic properties of ferritic steels [14, 15] or the oxidation resistance of Ti- aluminides [16]. Regarding the corrosion behaviour and biocompatibility of these novel intermetallic coatings, little work has been published. From the biomedical viewpoint, the absence of Ni is pointed out as a significant advantage, whereas the high Al M. A. Arenas (&) Á E. Frutos Á A. Conde Á J. L. Gonza ´lez-Carrasco Centro Nacional de Investigaciones Metalu ´rgicas, CENIM- CSIC, Avda. Gregorio del Amo 8, 28040 Madrid, Spain e-mail: geles@cenim.csic.es E. Frutos Á L. Saldan ˜a Á L. Labajos-Broncano Á M. L. Gonza ´lez-Martı ´n Á J. L. Gonza ´lez-Carrasco Á N. Vilaboa Centro de Investigacio ´n Biome ´dica en Red de Bioingenierı ´a, Biomateriales y Nanomedicina CIBER-BBN, Saragossa, Spain L. Saldan ˜a Á N. Vilaboa Hospital Universitario La Paz-IdiPAZ, Paseo de la Castellana 261, 28046 Madrid, Spain L. Labajos-Broncano Á M. L. Gonza ´lez-Martı ´n Departamento de Fı ´sica Aplicada, Universidad de Extremadura, Av. Elvas s/n, 06071 Badajoz, Spain 123 J Mater Sci: Mater Med (2011) 22:1005–1014 DOI 10.1007/s10856-011-4284-9