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In this study, an Al2O33D/5083 Al composite was fabricated by infiltrating a molten 5083 Al alloy into a three-dimensional alumina reticulated porosity ceramics skeleton preform (Al2O33D) using a pressureless infiltration method. The corrosion resistance of 5083 Al alloy and Al2O33D/5083 Al in NaCl solution were compared via electrochemical impedance spectroscopy (EIS), dynamic polarization potential (PDP), and neutral salt spray (NSS) tests. The microstructure of the two materials were investigated by 3D X-ray microscope and scanning electron microscopy aiming at understanding the corrosion mechanisms. Results show that an Al2O33D/5083 Al composite consists of interpenetrating structure of 3D-continuous matrices of continuous networks 5083 Al alloy and Al2O33D phase. A large area of strong interfaces of 5083 Al and Al2O33D exist in the Al2O33D/5083 Al composite. The corrosion development process can be divided into the initial period, the development period, and the stability period. Al2O33D used as reinforcement in Al2O33D/5083 Al composite improves the corrosion resistance of Al2O33D/5083 Al composite via electrochemistry tests. Thus, the corrosion resistance of Al2O33D/5083 Al is higher than that of 5083 Al alloy. The NSS test results indicate that the corrosion resistance of Al2O33D/5083 Al was lower than that of 5083 Al alloy during the initial period, higher than that of 5083 Al alloy during the development period, and there was no obvious difference in corrosion resistance during the stability period. It is considered that the elements in 5083 Al alloy infiltrated into the Al2O33D/5083 Al composite are segregated, and the uniform distribution of the segregated elements leads to galvanic corrosion during the corrosion initial period. The perfect combination of interfaces of Al2O33D and the 5083 Al alloy matrix promotes excellent corrosion resistance during the stability period. [ABSTRACT FROM AUTHOR]

Interface problems and the destruction of the continuity of the oxide film in the Al matrix usually reduce the corrosion resistance of the material. In this paper, the corrosion resistance of Al matrix composites (AMCs) was improved by introducing the silicon carbide skeletons (SiC3D) obtained with polymer replica technology. SiC3D/6061Al was fabricated by infiltrating molten 6061Al alloy in the oxidized SiC3D using the low-pressure casting method. The corrosion resistance performances of 6061Al and SiC3D/6061Al in NaCl solution were studied by electrochemical, neutral salt spray corrosion (NSS), and salt leaching (SL) tests. Results show corrosion resistance of SiC3D/6061Al is higher than that of 6061Al alloys by open circuit potential (OCP), potentio-dynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. However, NSS and SL tests show the corrosion resistance of SiC3D/6061Al is lower than that of 6061Al alloy. The reason is a corrosion resistant and anti-oxidation network macrostructure with large interface recombination, few concentrated interfaces, and a small specific area that formed in SiC3D/6061Al. SiC3D cannot damage the continuity of the Al2O3 passivating film, and the network macrostructure greatly improves the corrosion resistance performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A ceria doped aluminum phosphate ceramic coating was fabricated on cast Al-Si alloy by steam-assisted curing method. • The composite coating was composed of AlPO 4 and CeO 2. • Doping with a proper amount of nano-CeO 2 can improve the corrosion resistance of the aluminum phosphate ceramic coating significantly. • The long-term corrosion performance of the composite coating can be greatly improved by doping appropriate amount of CeO 2. A series of aluminum phosphate ceramic coating with the entrapped ceria (CeO 2) nanoparticles, which is denoted APC, were constructed by steam-assisted curing method on cast Al-10Si alloy. The composition, structure and morphology of the coatings were investigated using FT-IR, XRD, XPS and SEM. Moreover, the corrosion properties of coatings were evaluated by the electrochemical tests. All the coatings were demonstrated to be homogeneous, compact on the substrate surface. The appropriate amount of CeO 2 can effectively improve the corrosion resistance and durability of the coating. In addition, the formation and corrosion resistance mechanism of the coatings were studied in this work. [ABSTRACT FROM AUTHOR]

• Modified mullite particles with micro-nano structure have good hydrophobicity. • The superhydrophobic coating was successfully prepared via a simple dip-coating method. • The superhydrophobic coating has enhanced anti-corrosion performance. • The superhydrophobic coating exhibits excellent mechanical durability and chemical stability. In this paper, a multiple hybrid coating (MHC) with good corrosion resistance and superhydrophobic property on the surface of cast Al–Si alloy was synthesized via a simple dip-coating method by using organosiloxane containing hydrophobic mullite-SiO 2 (M–S) particles as a precursor. The morphology, composition and water contact angle (WCA) of the coatings were investigated by SEM, FT-IR, XRD and OSA100, respectively. The results showed that the hydrophobic M–S particles was synthesized through modified Stöber method, which has a micro- and nano- scale structures. In addition, the morphology of the MHC presented that a dense and uniformly cover on the Al–Si alloy substrate formed a superhydrophobic surface with the WCA ∼153.4°. The corrosion protection of MHC was evaluated by using the Tafel polarization curves and electrochemical impedance spectroscopy. The coating with M–S particles exhibited much better corrosion resistance property than that of the untreated substrate and pure organosiloxane coating (OSC). The E corr was obviously more positive than that of them. Moreover, the corrosion current density of MHC was remarkably decreased by 5 and 3 orders of magnitude compared with other two coatings, respectively. The corrosion resistance of the MHC decreased gradually with increasing immersing time. However, the R ct value of MHC was still 2.31 × 106 Ω cm2 after 168 h immersion testing in 0.6 M NaCl solution, which was nearly 322-fold higher than that of untreated substrate. Owing to the excellent superhydrophobic, corrosion resistance and long-term stability, the MHC possesses potential application in corrosion resistance of cast Al–Si alloy. [ABSTRACT FROM AUTHOR]