Development of active modified kaolin as anticorrosive fillers

Intercalation of kaolin by urea molecules via mechanical grinding resulted in partial delamination with some broken bonds between kaolin layers. This permits subsequent modification by either active APTES (3-amino propyl triethoxy silane) or urea-formaldehyde polymer chains. Therefore, this study aims to develop new active fillers depends on modified kaolin and encapsulated modified kaolin which are considered as new encapsulated corrosion inhibitors. A type of these encapsulated active fillers, the intercalated kaolin by urea (UK) was silylated with APTES then coated by a shell of urea-formaldehyde polymer through in-situ polymerization method. Another type, UK was modified by urea-formaldehyde polymer and then coated by APTES layer. All the prepared fillers were characterized by FTIR, X-ray diffraction, thermal analysis, SEM and EDX measurements. Then, varnish formulations contain 10% of prepared fillers and alkyd resin were coated to mild steel surface to study their efficiency as anticorrosive fillers by electrochemical impedance spectroscopy (EIS). The results indicated that APTES was successfully grafted on to the surface of kaolin and in between its exfoliated layers and urea-formaldehyde polymer formed a continuous shell encapsulating the active silylated kaolin molecules. Additionally, the encapsulated filler UK-UF-AP has superior anticorrosive properties for steel protection.