High-solids, one-coat paints based on aliphatic epoxy resin-siloxanes for steel protection

Abstract

This research involved the design of high-solids, one-coat paints for the protection of metal structures with low maintenance requirements. The main paint components were: (i) an aliphatic epoxy resin cured with an aminosilane and chemically modified with alkoxysilanes as film-forming material, and (ii) rutile titanium dioxide as opaque pigment, a polysilicate strontium and zinc as corrosion inhibitor and, a synthetic calcium silicate and barites as extenders. Some paints displayed excellent performance in salt spray apparatus (degree of rusting) and in 100% relative humidity cabinet(degree of blistering). Results indicate that as the aliphatic epoxy resin/alkoxide ratio increased, the degree of rusting improved while the degree of blistering worsened, in total agreement with film permeability. In addition, binders based on dimethyldiethoxysilane, methyltriethoxysilane and tetraethoxysilane, in that order, displayed an improved corrosion performance and a decreased blistering resistance. The reactivity of alkoxides and the chemical interaction with the metal substrate supports the obtained results. Initial gloss and gloss and color retention improved as the alkoxide level increased; no significative differences were registered when the alkoxide type variable was considered. In summary, the use of alkoxides as modifiers of an aliphatic epoxy resin allowed the formulation of hybrid paints with high anticorrosive and weathering resistance performance. The more suitable hybrid organic–inoganic paint must be selected according to the requirements of each structure in service.