Influence of experimental parameters using the dip-coating method on the barrier performance of hybrid sol-gel coatings in strong alkaline environments

摘要

Previous studies have shown that the barrier effect and the performance oforganic-inorganic hybrid (OIH) sol-gel coatings are highly dependent on the coatingdeposition method as well as on the processing conditions. However, studies on how thecoating deposition method influences the barrier properties in alkaline environments arescarce. The aim of this experimental research was to study the influence of experimentalparameters using the dip-coating method on the barrier performance of an OIH sol-gelcoating in contact with simulated concrete pore solutions (SCPS). The influence of residencetime (Rt), a curing step between each dip step and the number of layers of sol-gel OIH filmsdeposited on hot-dip galvanized steel to prevent corrosion in highly alkaline environmentswas studied. The barrier performance of these OIH sol-gel coatings, named U(400), wasassessed in the first instants of contact with SCPS, using electrochemical impedancespectroscopy and potentiodynamic methods. The durability and stability of the OIH coatingsin SCPS was monitored during eight days by macrocell current density. The morphologicalcharacterization of the surface was performed by Scanning Electronic Microscopy beforeand after exposure to SCPS. Glow Discharge Optical Emission Spectroscopy was used toinvestigate the thickness of the U(400) sol-gel coatings as a function of the number of layersdeposited with and without Rt in the coatings thickness.