Corrosion Protection of Aluminum by Hydrophobization Using Nanoparticle Polymer Coatings Containing Plant Oil

A polymer coating for corrosion protection of aluminum surfaces (AA 1050A) was evaluated, including styrene maleimide nanoparticles synthesized in aqueous dispersion by imidization of poly(styrene-co-maleic anhydride) in presence of vegetable oils (SMI/oil). Different nanoparticle coatings with mono- and poly-unsaturated oils were evaluated through Raman spectroscopy, water contact angle measurements and atomic force microscopy (AFM). One type of nanoparticles with soy oil was selected based on the high oil reactivity and formation of homogeneous coating with low content of free oil, high degree of imidization, high hydrophobicity and long-term stability. After optimization of the coating composition, the organic nanoparticles were mixed with 20 wt.% carnauba wax and 50 wt.% styrene/butadiene, resulting in a contact angle of 109 degrees. The aluminum surfaces were pre-treated under different conditions including phosphatization or alkaline etching, and dip-coating speed variation. The best corrosion resistance after salt-spray testing occurs for samples that were etched for 10 s at 25 degrees C, followed by dip-coating at 125 mm min(-1). The resulting coating layer is relatively thin, but with good corrosion resistance in parallel with the highest contact angle values and slightly higher average surface roughness than coatings deposited at low speeds.