Cyclodextrins as Carriers for Organic Corrosion Inhibitors in Organic Coatings

Abstract

© The Author(s) 2017. Published by ECS. All rights reserved. Coatings are widely applied on metal surfaces for protection against corrosion. Once a coating is damaged and a defect is filled by aqueous solutions, delamination of the coating initiates further materials degradation. Cathodic delamination can be suppressed by adding active additives to the coating matrix. In this study, the impact was investigated of β-cyclodextrin inhibitor complex (β-CD[Inh]) additives in polyvinylbutyral model coatings on the cathodic delamination of coatings on zinc, using the scanning Kelvin probe (SKP). With the presence of the β-CD[Inh] in the coating, a decrease was observed of the delamination rate to 1/4 of that in the reference system without β-CD[Inh]. Release experiments using UV-Vis spectroscopy showed that in the presence of cyclodextrins, the released concentration of the inhibitor 2-mercaptobenzothiazole from the coating increased. The increase was most pronounced under alkaline conditions, where the released concentration within 24 h increased by a factor of 6 compared to a reference system without β-CD. The delamination experiments performed with 0.1 M KOH in the defect showed a quick stop of the delamination. When 1 M KCl was used as electrolyte, the defect potential rose after 16 h to the passive potential of zinc, if a sufficient amount of β-CD[Inh] was present in the polymer model coating.