Novel protective coatings for steel based on a combination of self-assembledmonolayers and conducting polymers

摘要

Coatings technology has for a long time been only a macroscopic technology. Nowadays,rnhowever, new techniques have become available which allow the design of a very corrosionrnresistant metal/coating interface on a sub-micron or even molecular level.rnA very stable metal/polymer interface may be built up by the use of self-assembling adhesionpromotingrnmonolayers of suitable organic substances. In a running research project suchrnmonolayers are investigated using special taylored molecules, containing anchor-groupsrnwhich are able to bind onto the iron surface, spacers (normally alkyl-chains) and head-groups,rnwhich are able to polymerise with each other. As anchor-groups phosphonic acids are used,rnwhich were already sucessfully investigated to produce stable monolayers on iron. As headgroupsrnspecial self-synthesized thiophene derivatives are used, which can be electrochemicallyrnor chemically polymerised under moderate conditions. As it will be shown from thernresults obtained so far these monomers are able to self-assemble to a monomolecular film,rnwhich can afterwards be polymerized to a monomolecular layer of a conducting polymer. Duernto its electrical conductivity such a layer is suitable for covering with a conventional electrophoreticrnprimer. In this way the metal/coating interface can be well-designed and adhesionrnpromotion is achieved. Furthermore the interface may be adjusted to a hydrophobic state,rnwhich in turn should lead to an enhanced corrosion resistance of the interface as water isrnnecessary for the corrosion process.rnThe new coating system will be introduced and the results obtained so far will be shown. Thernnew coatings have been characterized concerning their adhesion properties, their electrochemicalrnproperties as well as their effect on corrosion kinetics.