Enhancement Of The Durability Of A Polyamide Coating: Incorporation Of An Aminosilane Into The Powder Formulation

Polymer-based coatings are widely used to protect steel from corrosion. A high level of adhesion between the coating and the steel substrate is essential if good corrosion protection is to be achieved. In the current work we explore the use of a silane adhesion promoter added to the powder stock prior to coating.A study has been undertaken on a polyamide 11 based powder coating on a steel substrate. Powders have been prepared, based on the reference product with addition of APS ((3-aminopropyl) triethoxysilane, NH(2)-(CH(2))(3)-Si(O-CH(2)-CH(3))(3)) at different concentrations.The extent of delamination after salt-spray testing has been documented and, for all coatings which incorporated the aminosilane, is reduced. Characteristic features of the delamination process have been obtained by AES. The enhanced durability is shown to result from the segregation of a layer of the organosilane to the interfacial region. Using a microtome taper sectioning method, a profile of the aminosilane within the thickness of the coating has been obtained. The bond between aminosilane and steel is probably covalent in nature as indicated by the presence of a specific ion Fe-O-Si(+) observed by high-mass resolution ToF-SIMS. Thus, the effect is similar to that achieved by the deposition of a discrete silane layer prior to coating application. Copyright (C) 2004 John Wiley Sons, Ltd.