Preparation Of Siloxane-Polyurethane Hybrid Coatings By The Sol-Gel Method Applied On Zamac Plates

Luís Fernando Flach Mendieta¹, Sandra Raquel Kunst², Fernando Dal Pont Morisso¹,
Luana Góes Soares¹*, Cláudia Trindade Oliveira¹, Carlos Leonardo Pandolfo Carone¹

¹Universidade Feevale, ICCT, endereço institucional (Rod. RS239, n.2755, Bairro Vila Nova), Novo Hamburgo, Rio Grande do Sul, (BRASIL)
²Projeto de Fixação de Recursos Humanos do CNPq – Nível A (RHAE) – CNPq, Sapucaia do Sul – RS, (BRASIL)

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ABSTRACT – 

Corrosion in metals represents a high maintenance cost and is a factor in choosing the material depending on its application. This study seeks a surface treatment for metals with the aim of increasing their anticorrosive properties. In this work, siloxane-polyurethane hydrocoatings were developed and deposited by dip-coating on zamak plates. The hybrid sols were prepared by the synthesis of polyurethane (PU), from the reaction of polycaprolactone diol with hexamethylene diisocyanate (HDI) in different ratios of NCO:OH, 1.7:1, 1.8:1 and 1.9:1, followed by acid hydrolysis/polycondensation of the tetraethoxy-silane (TEOS) systems added to each system according to the free NCO ratio. The coatings obtained were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), contact angle, thermogravimetric analysis (TGA), dynamic-mechanical analysis (DMA) and differential scanning calorimetry (DSC). The films applied to zamac 5 were evaluated for corrosion by electrochemical impedance spectroscopy (EIE) and open circuit potential (OCP). The PU+TEOS synthesis allowed the preparation of a polyurethane-siloxane hybrid material with a cross-linked structure. Based on the results, the best ratio was 1.7:1 NCO:OH and addition of 0.7 mol of TEOS, as it presented better homogeneity as well as better performance in terms of corrosion resistance.