Interface between cement paste and thin TiN film for corrosion resistance enhancement; structural, morphological and electrochemical properties Elena Cerro Prada a,⇑ , Vicente Torres Costa b,1 , Pilar Herrero Fernández c,2 , Giacomo Ceccone d,3 , Miguel Manso Silván e,1 a Civil Engineering Department, Universidad Politécnica de Madrid, C/Alfonso XII, 3 y5, 28014 Madrid, Spain b Applied Physics Department, Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, 28049 Madrid, Spain c Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain d European Commission, DG JRC, Unit Nanobiosciences, Via E. Fermi 2749 TP203, I21027 Ispra (VA), Italy e Applied Physics Department and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, 28049 Madrid, Spain highlights  Utilization of Ti-based nanostructures for modification of cement paste.  TiN thin films effectively provide physical protection to reinforcing steel in concrete against chloride-induced corrosion.  The cement paste in contact with TiN develops adhesion phases which enrich the passive layer.  Crystalline clusters of C–S–H were found at the interface between TiN/cement.  High corrosion resistance in chloride environment was assessed in TiN/cement interfaces. article info Article history: Received 10 October 2013 Received in revised form 4 December 2014 Accepted 2 January 2015 Keywords: Cement paste microstructure Portlandite Ettringite Nanocrystalline C–S–H TiN coating Chloride-induced corrosion Potentiodynamic polarization abstract TiN thin films prepared by magnetron sputtering have been evaluated as corrosion protective coatings for potential applications in concrete reinforcing steel. The interface between the cement paste and the TiN at several curing temperatures has been investigated by means of X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. Potentiodynamic polarization scans in a chloride buffer have been applied to establish the corrosion resistance modification of the nitride coatings after cement paste curing and setting. The results show that the augmented portlandite formation at the cement–TiN interface exhibits a clearly preferred orientation with (0 0 1) plane parallel to the interface. Nanosized C–S–H crystals are detected on the TiN coating, arranged in clusters. The local increase in the w/c ratio occurring at the interface promotes, along with high temperature exposition, the formation of micrometric ettringite dominantly at the interfacial zone. Electrochemical measurements reveal that TiN coatings show a superior corrosion behavior after cement paste setting. Published by Elsevier Ltd. 1. Introduction Anhydrous cement consists mainly of tricalcium silicate Ca 3 SiO 5 (50–70% wt%) and dicalcium silicate Ca 2 SiO 4 (15–45%), which form, upon hydration, amorphous calcium silicate hydrate (C–S– H) and well-crystallized calcium hydroxide (Ca(OH) 2 , portlandite). Cement (mainly alkaline portlandite) naturally provides protection against corrosion of the steel armor in reinforced concrete by maintaining a high pH at the interface (pH > 13.5), which promotes the formation of a thin passivating oxide (26 nm) [1]. However, various pollutants to the concrete environment can modify this passivating behavior leading to significant corrosion of steel. Corrosion of reinforcing steel bars in concrete is a significant problem from the point of view of structural integrity with drastic economic consequences. One of the major contributors to the http://dx.doi.org/10.1016/j.conbuildmat.2015.01.007 0950-0618/Published by Elsevier Ltd. ⇑ Corresponding author. Tel.: +34 91 33677 52; fax: +34 91 336 79 55. E-mail addresses: elena.cerro@upm.es (E. Cerro Prada), vicente.torres@uam. es (V. Torres Costa), pherrero@icmm.csic.es (P. Herrero Fernández), giacomo. ceccone@jrc.ec.europa.eu (G. Ceccone), miguel.manso@uam.es (M. Manso Silván). 1 Tel.: +34 91 497 88 08; fax: +34 91 497 39 69. 2 Tel.: +34 913449012. 3 Tel.: +39 0332785475; fax: +39 0332785787. Construction and Building Materials 80 (2015) 48–55 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat