Surface pretreatment coatings are a research area in continuous transformation. Moving away from the well-known chromium conversion coatings (CCC) toward an environment-friendly alternative is of great interest. Here we present a polymer-clay coating made from branched polyethylenimine (BPEI) and montmorillonite (MMT) clay, as a potential CCC substitute. This polymer-clay coating is easily applied by airbrushing an aqueous BPEI/MMT mixture onto any substrate (e.g. aluminum alloy 2024-T3). With this approach, application time is significantly reduced in comparison to other techniques (e.g. layer-by-layer assembly), and the structure of the polymer-clay coating is finely tuned by controlling the polymer-clay ratio. Results from electrochemical measurements and salt spray testing reveal excellent long-term (40d) corrosion protection provided by a 1.8 μm thick coating with a 20:80 polymer-clay ratio. This polymer-clay ratio yields a highly ordered multilayered brick and mortar structure, where MMT (bricks) provides a physical barrier for the diffusion of corrosive agents/corrosion products within the coating, and BPEI (mortar) provides structural support and decelerates the corrosion process through surface buffering.

Polymer-clay nanocomposite coatings as efficient, environment-friendly surface pretreatments

255th National Meeting (2018)

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