Lubrication, wear resistance and corrosion protection on aluminum alloy toward multifunctional coatings with nano-CeO2 inhibition effect

The coupling effect of wear and corrosion aggravates the damage and failure of key moving parts of high-end equipment, leading to a significant reduction in their service life. In present work, a functional integrated composite coating with exceptional corrosion resistance and tribological properties was developed by utilizing the responsive corrosion inhibition of nano-cerium oxide (nano-CeO2) and the low surface energy and low shear characteristics of polytetrafluoroethylene (PTFE). The tribological behaviors and corrosion protection performance of coatings on aluminum alloy 2024 were evaluated and the corrosion inhibition mechanism was further discussed. The results revealed that Ce3+ on the surface of nano-CeO2 reacts with OH- generated by the REDOX reaction of the cathode to produce a uniform and stable passivation film, which can effectively improve the corrosion resistance of the metal matrix. Notably, the most obvious passivation effect is presented when the 2 % addition of nano-CeO2 as the larger low-frequency impedance modulus of 4.49 x 1010 omega & sdot;cm2 and higher phase angle of 88 degrees. The introduction of PTFE not only changes the coating from hydrophilic to hydrophobic, but also further improves the shielding properties of the coating. The low-frequency impedance modulus of the coating further increases by an order of magnitude to 2.38 x 1011 omega & sdot;cm2, and its neutral salt spray resistance exceeds 210 days. Besides, the friction coefficient is reduced by 77.43 % and the wear resistance improved by 6.8 times compared with phenolic epoxy coating. Due to the enhancement and corrosion inhibition effect of nano-CeO2, the lower friction coefficient (0.044) and good wear resistance are further presented under the corrosive medium condition of 3.5 % NaCl solution.