Interface between cement paste and thin TiN film for corrosion resistance enhancement; structural, morphological and electrochemical properties

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.