It is important to find environmentally-friendly replacements for chromate conversion coatings (CCCs) that are effective anticorrosion layers. In this work, high corrosion resistance is demonstrated with ultrathin (and transparent) multilayer coatings deposited on an aluminum alloy. Cationic waterborne polyurethane (PU) and anionic vermiculite clay (VMT) multilayer films were deposited layer-by-layer and compared with polyethleneimine (PEI)/VMT multilayers on aluminum. The combination of relatively hydrophobic polyurethane and highly aligned clay platelets leads to better barrier properties for the PU/VMT coating in an aqueous environment. A 30 bilayer PU/VMT coating, with a thickness of only 300 nm, provides two orders of magnitude improvement in impedance and imparts corrosion protection for five days, which is comparable to other composite coatings that are two orders of magnitude thicker. Another advantage of this unique coating system is that no surface treatments are required prior to coating due to the strong adhesion of polyelectrolytes to the metal. The environmental-friendliness, ease of production and excellent corrosion resistance make these LbL-assembled PU/VMT coatings a potential replacement for undesirable chromate conversion coatings.

Ultrathin nanobrick wall anticorrosion coatings

256th National Meeting (2018)

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