Upscaling challenges for LDH-containing active protection coatings

• Autor(a) principal: Franco, Filipe André Heliodoro
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/12302
• topic: Engenharia de materiais; Corrosão - Testes de materiais; Anticorrosivos; Revestimentos protectores; Hidróxidos duplos laminares

The main goal of this work is to study the challenges associated to the upscaling of an active protective coating with (LDH) layered double hydroxides from a laboratorial to industrial scale. Two types of coatings having LDH with gluconate intercalated into its galleries with and without alginate as surface modification were considered. Dispersion was studied with both particles in a polymer formulation and it was shown that the addition of alginate allows a faster and more effective dispersion as well as improved compatibility to the matrix. The possible agglomeration of LDH particles in the formulation was evaluated by particle size analysis demonstrating a reasonable compatibility between the pigment and polymer. The developed coatings were studied with standard accelerated corrosion tests and electrochemical techniques demonstrating active protection conferred by the LDH nanocontainers. Coating protection properties were studied through electrochemical impedance spectroscopy and revealed that the addition of LDH allows an active corrosion protection to coatings, higher impedance values and a delay on the appearance of new time constants with the increasing of immersion time. The shelf-life of the LDH pigment as well as LDH-containing coating formulation was estimated by monitoring the crystalline structure of LDH by X-ray diffraction technique. No changes of LDH structure during storage in open air were observed, however, for formulation, there was a change of basal spacing which can be associated to intercalation of anionic species from formulation into LDH galleries. The obtained results lead to the conclusions that the compatibility of LDH with coating formulation can be improved by modification of pigment particles with alginate when considering pre-industrial scale application. The shelf life of the formulation can be extended if the LDH nanocontainers are added at a later stage shortly before the coating application.