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For the corrosion protection of steel rebars in concrete, five different molybdate-phosphate conversion coatings were prepared, by changing the molybdate-phosphate ratio in the conversion baths. Their composition and morphology were studied with GD-OES, XPS, Raman spectroscopy and SEM-EDX and a schematic representation of their structure is suggested. Further, the corrosion resistance properties of the coatings were evaluated in a simulated concrete pore solution (CPS) containing chlorides, using anodic polarization measurements. Thanks to the elaborated surface analysis their corrosion behaviour could be correlated to their structure. The results show that by altering the molybdate-phosphate ratio the structure and, consequently, the corrosion protection properties change significantly. By optimizing this ratio a twofold protection mechanism could be attained, demonstrating both good barrier properties and consistent with active corrosion protection.

Sodium molybdate is evaluated as corrosion inhibitor for steel in brackish water; it is encapsulated by interfacial polymerization and the produced capsules are characterized. Electrochemical impedance spectroscopy and corrosion potential measurements were used to determine the short-time corrosion inhibition while polarization curves were used for the estimation of the inhibition efficiency. The capsules composition, the Na 2 MoO 4 content and the release rate are then determined. Na 2 MoO 4 shows corrosion inhibition for at least 15 h. Capsules consist of polyurea and polyurethane which are formed due to the reaction of the isocyanates with the water of the emulsion and the used surfactants, respectively. Most of the inhibitor is released within 90 min. Electrochemical Impedance Spectroscopy and Scanning Vibrating Electrode Technique show corrosion inhibition on artificially damaged areas for the coatings containing the corrosion inhibitor capsules.

By positioning the layer containing Ce ( dbp ) 3 close to the coating–metal interface, the effective use of the inhibitor is promoted, as the leaching out towards the metal surface is facilitated. The chemical nature of Ce ( dbp ) 3 did not undergo any significant change due to the plasma discharge. The coatings with Ce ( dbp ) 3 were compared with equivalent coatings without incorporated corrosion inhibitor and it was shown that Ce ( dbp ) 3 improved the corrosion performance when the coating was mechanically damaged. Optical evaluation of the coatings showed a significant decrease in the corrosion, especially in the area under the coating. However, the low corrosion resistance values obtained by electrochemical impedance spectroscopy indicate that corrosion was not inhibited all over the scribed area.