A novel chitosan-stearic coating with bee-pollen microcapsules for corrosion protection

Abstract: In this project a novel chitosan-stearic acid (CS-SA) coating with bee-pollen microcapsules for encapsulation of 2-mecraptobenzothiazole (MBT) as a waterborne formulation for a biocompatible corrosion protection coating was developed and the coating properties was analyzed. Hydrophobic stearic acid (SA) was crosslinked with via a carbodiimide reaction to form micelles and is assembled on the bee- pollen grains and the chitosan matrix was further self-crosslinked using glutaraldehyde (GA). Stearic acid was used to hydrophobically interact with modified pollen and with further crosslinking with the chitosan, which was proven successful by FTIR results. The encapsulation of anticorrosive agent MBT into pollen was successful and examined by UV-Vis spectroscopy, however, the pollen cannot form a fully stable formulation with the chitosan micelle matrix, partially due to its relatively big size (ca. 20 μm), causing problems with forming a proper barrier protection. The size of the grains and the interference of the carbodiimide crosslinking is the most severe problems with the pollen microcapsules. Therefore, no further testing of the corrosive properties could be done, which requires a dense and stable coating to sustain in salty water for the whole measurement period. As the reference coatings without pollen provided much more promising results, especially when crosslinked with GA, the conclusion is that the reactivity of the pollen is proven difficult to crosslink, and choosing a proper size of a microcontainer and the appropriate encapsulation method in the binder matrix is vital and important for developing a corrosion protective coating.