An ultra-flexible, chromate-free, low-VOC, silane-based finishing and coating system for corrosion protection of aluminum alloys
Abstract-The capability of silanes to replace chromate in pretreatments and primer systems has been firmly established by Van Ooij et al. This paper provides an overview about the role of silanes in a two-component (silane and water-based resin) coating system for corrosion protection of aluminum alloys. The coating system consists of a two-component primer (AV5 silane, a 5:1 mixture of bis-trimethoxysilylpropyl amine and vinyltriacetoxysilane and an epoxy resin) and a two-component topcoat system (bis-sulfur silane and polyurethane resin). The coating is a low-VOC, chromate-free, highly flexible, environmentally-benign system with protective performance comparable to that of commercial chromate-containing primers. This coating system does not require the use of conversion coatings on metals. Nanoparticles, inhibitors and other additives can be incorporated in order to further improve the mechanical properties of the coating. Various corrosion tests and characterization techniques have been employed to illustrate the corrosion protection properties of the coating system on metals such as aluminum alloys. Standard ASTM tests, such as the tape adhesion test, pencil hardness test and bend test, were also employed. Some results of these tests are presented.