Hybrid coatings based on conducting polymers and polysiloxanes

摘要

We have developed a new promising approach that allows to obtain a composite film containing polypyrrole units and polysiloxane linkages in a simple way using a pyrrolil silicon compound as a primer on as-received wrought Al alloys. The outstanding corrosion protection, with respect to conventional organofunctional silanes and polypyrrole films, was attributed to the following relevant characteristics: (i) higher degree of compactness and thickness, resulting from the primer molecule crosslinking via silanol groups condensation and pyrrole rings couplings; (ii) improved adhesion due to preferential adsorption and condensation of silanol groups at the metal/film interface; (iii) mixed protection in terms of passive (barrier) and active (anodic) actions provided by polysiloxane and polypyrrole chains within the composite network, respectively. Further confirmation of the validity of this approach as applied on low carbon steel and hot-deep galvanized steel have been obtained by different corrosion tests in correlation with spectroscopic characterization techniques, when compared to control coatings of poly-2H-imidazole-silane (PImSi) and polyoctylsilane (POSi). Structural/morphological characterization of the coatings, as well as the investigation of PySi solution by different spectroscopic techniques, in addition to corrosion tests in NaCl, strongly support the very promising protection performance of the hybrid film. This is indicated as well by the preliminary results obtained with aniline-based silane. Thus, typical silane-based treatments with principally barrier action can gain in active properties if the silane compound contains monomers of conducting polymers as a functional group.