Optimization of Ti/TiO2 multilayers deposition parameters for corrosion applications

Abstract

The theme of this research is the optimization of Ti/TiO2 multilayer deposition parameters for anti-corrosion applications. The problem in question is to study the effectiveness of these coatings in the protection against corrosion. We expect to have multilayers that have a high resistance against corrosion. The main purpose of this study is to see the possibility of the use of multilayer deposits for corrosion protection purposes and especially in the industry that suffers from the phenomenon of corrosion.

In our work we used two deposition techniques: spin-coating gel sol to deposit titanium dioxide TiO2 and electroplating to deposit titanium Ti both on steel substrates. The deposit parameters by the two techniques were optimized. These are: spin speed, deposition time for spin coating; and the concentration of the bath, the deposition time, the temperature and voltage for electroplating. The structural characterization was made by X-ray diffraction (XRD), while the morphology and chemical composition were defined by scanning electron microscopy (SEM) and dispersive energy spectrometer (EDX).

2, 4, 6, and 8 layers of metal /oxide layer coatings Ti / TiO2 type were also realized to see the performance on corrosion protection. For this, corrosion tests were carried out on mono and multilayers coatings in a 0.1M HCl solution by electrochemical polarization.

The main results obtained in our study show that: - All the deposit coatings presented a very good adherence with substrate. - XRD and SEM analysis of TiO2 thin films show that films exhibited a good, morphology and amorphous structure in the optimal conditions which are 5000 rpm, 45 s and 0.5 Mol/L of solution concentration. - SEM and XRD investigations confirmed that the obtained Ti thin films gave best results in morphology and chemical composition at room temperature, 15 V and 5 minutes. - SEM and XRD characterization show great results in Ti/TiO2 multilayer with 6 films compared to others in morphology properties. - Ti/TiO2 multilayer coatings exhibited better corrosion resistance than Ti and TiO2 monolayer thin films. - The polarization curves and Tafel’s plots confirmed that the corrosion resistance has been improved or enhanced by Ti/TiO2 multilayer coatings; the Ti/TiO2 multilayer with 8 films exhibited the best corrosion protection because of the increased number of interfaces or layers and the decrease of cracks and stresses so The corrosion current density Icorr was decreased with the increase of number of layers.

Perspectives: • Study of the interfaces phenomena and its influence on corrosion resistance. • Using more sophisticated techniques such as XPS, SIMS for the determination of layers composition and corrosion products. • Possibility to increase the number of multilayers in order to study their corrosion behavior. • Use of PVD methods to elaborate multilayer films.

In this work, Ti and TiO2 thin films deposited onto stainless steel using Electrodeposition and sol gel spin coating processes respectively in order to realize the Ti/TiO2 multilayer coatings with different number of films. Surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and x ray electron dispersive spectrometer (EDX) methods. Their corrosion behavior was tested in 10wt% hydrochloric (HCl) acid. The results showed that the optimal conditions for Ti electroplating are 15 V, 5 min and room temperature and the parameters which gave the best spin-coated TiO2 thin films are 0.5 mol/L, 5000 rpm and 45 seconds. After polarization tests and corrosion densities measurements, the results showed a higher multilayer corrosion resistance than that of single layers. This result can be attributed to the increase in number of layers which could enhance and improve the protection against corrosion. Keywords: Ti/TiO2, multilayer, electrochemical corrosion, optimization, electroplating.

Résumé Dans ce travail, des couches minces de Ti et TiO2 sont déposées sur acier en utilisant l'électrodéposition et la technique sol-gel respectivement dans le but de réaliser des revêtements multicouches Ti/TiO2 en variant le nombre de couches. La morphologie de la surface et la composition chimique ont été caractérisées par microscopie électronique à balayage (MEB) et spectroscopie dispersive des rayons X (EDX). Leur comportement face à la corrosion a été étudié dans l'acide hydrochlorique (HCl) à 10 % wt. Les résultats ont montré que les conditions optimales pour l'électrodéposition de Ti sont 15 V, 5 min et température ambiante. Les paramètres qui donnent les bons films par spin-coating sont 0.5 mol/L, 5000 rpm et 45 secondes. Après les tests de polarisation et les mesures de densités de corrosion, les résultats ont montré que la résistance à la corrosion des multicouches est plus haute que celle d'une monocouche. Ce résultat peut être attribué au fait que l'augmentation du nombre de couches augmente la protection contre la corrosion. Mots clés: Ti/TiO2, multicouches, corrosion électrochimique, optimisation, électrodéposition.