Effect of Cerium and Magnesium on Surface Microcracks of Al–20Si Alloys Induced by High-Current Pulsed Electron Beam

The effect of Ce and Mg on surface microcracks of Al–20Si alloys induced via high-current pulsed electron beam (HCPEB) was studied. Mg was revealed to refine the primary Si phase in the pristine microstructure by forming a Mg2Si phase, leading to the suppression of microcrack propagation within the brittle phase after HCPEB irradiation. The incorporation of Ce into the Al–Si–Mg alloys further refined the primary Si phase and reduced the local stress concentration in the brittle phase induced by HCPEB irradiation. Ultimately, the surface microcracks were observed to be eliminated by the synergistic effects between the two elements. For Al–20Si–5Mg–0.7Ce alloys, Ce demonstrated a homogeneous distribution in the Al matrix on the HCPEB-irradiated alloy surface, while the Mg and Si exhibited a certain degree of aggregation in the Mg2Si phase. Metastable structures were formed on the HCPEB-irradiated alloy surface, including the nano-primary silicon phase, nano-cellular aluminium structure, and nano-Mg2Si phase. Compared with alloy specimens containing Mg, the Al–20Si–5Mg–0.7Ce alloy specimens exhibited an excellent anticorrosion property after HCPEB irradiation mainly due to the combined effects of the grain refinement and microcrack elimination.

Evaluation of Electrochemical and Anticorrosion Properties of Polyaniline-Fly Ash Nanocomposite

In India, the thermal station generates approximately 6.9 × 10 7 tons of fly ash (FA) as a waste by-product. As part of this work, little attempt was made to produce useful materials from waste material. In our current research, polyaniline- (PANI-) fly ash (FA) nanocomposite (PFNC) was synthesized using an in situ polymerization method. The synthesized composites were characterized by employing advanced analytical, microscopic, and spectroscopic tools. The results of the X-ray diffraction (XRD) analysis confirm the effective reinforcement of FA into PANI in PFNC. The presence of functional groups in PFNC has been confirmed by Raman and FT-IR spectroscopic techniques. The SEM micrographs of the nanocomposite revealed the presence of agglomerated and fragmented structures in PFNC. The weight loss for PFNC was observed to occur in three stages as revealed by thermogravimetric analysis (TGA). UV-visible spectra for PFNC proved that FA stabilized the PANI in emeraldine form. Electrodynamic polarization studies were conducted to explore the corrosion resistance of nanocomposite-coated mild steel. The corrosion current density ( i corr ) for PFNC-coated mild steel (MS) specimens was found to decrease when compared to the bare substrate, indicating superior corrosion resistance in PFNC-coated substrate. Similarly, Tafel and cyclic polarization studies too confirmed superior anticorrosion property for MS coated with PFNC.

Anticorrosion Property of Alcohol Amine Modified Phosphoric and Tannic Acid Based Rust Converter and Its Waterborne Polymer-Based Paint for Carbon Steel

Four kinds of alcohol amines were tested to improve the anticorrosion performance of the phosphoric and tannic acid (PTA)-based rust converter. The alcohol amine modified PTA rust converters with the optimum mechanical and functional performances were used to prepare the homogeneous single-component waterborne rust conversion-based paint. The mechanical properties and the long-term corrosion resistance of the synthesized rust converter-based paint were investigated. The results show that alcohol amine modified PTA rust converter can convert the rust layer into a thick passivation film with iron tannate and iron phosphate as the main components, significantly improving the corrosion resistance of the carbon steel. The alcohol amine D modified PTA rust converter (RC-D) showed the best anticorrosion and rust conversion performances. The waterborne rust conversion-based paint can convert the rust layer of steel into a blue-black and relatively flat passivation film layer. The waterborne polymer-based paint containing 10 wt.% RC-D significantly improves the long-term corrosion resistance of the rusty steel and the mechanical property of paint.

APTES Modification of Molybdenum Disulfide to Improve the Corrosion Resistance of Waterborne Epoxy Coating

MoS2 has been regarded as a promising addition for the preparation of epoxy-based coatings with high anticorrosion ability. However, its dispersion and compatibility remain significant challenges. In the present work, an organic thin layer was well coated on lamellar molybdenum disulfide (MoS2) via a simple modification of 3-aminopropyltriethoxysilane (APTES). The modification of hydrolyzing APTES on lamellar MoS2 effectively improved the dispersity of MoS2 in water-borne epoxy (WEP) and successfully enhanced the compatibility and crosslinking density of MoS2 with WEP. The influence of introducing MoS2-APTES into WEP coating on anticorrosion property for N80 steel was tested by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and salt spray test. The results exhibited that the |Z|0.01Hz value of MoS2-APTES/WEP still reached 3.647 × 107 Ω·cm2 even after the immersion time of 50 days in 3.5 wt.% NaCl solution, showing an extraordinary performance of corrosion resistance. The enhanced anticorrosion performance of composite coating could be resulted from the apparently increased dispersibility and compatibility of MoS2 in WEP.

2024 ALUMINUM OXIDE FILMS PREPARED BY THE INNOVATIVE AND ENVIRONMENT-FRIENDLY OXIDATION TECHNOLOGY

A kind of environment-friendly anodic oxidation technology was used to oxidize 2024 aluminum alloys from mixed acid solutions to effectively improve the anticorrosion and mechanical performances. The influences of anode oxidation method on surface morphology, microstructure, composition, electrochemistry parameter, anticorrosion property were studied. Aluminum alloy oxidation is actually a dynamic equilibrium process of the formation and dissolution of oxide film which is composed of porous and non-porous layer. With the treatment of anodic oxidation, [Formula: see text]-Al2O3 and [Formula: see text]-Al2O3 structures were obtained on the surface of aluminum alloys, which contributed directly to the increase of anticorrosion performance. The potassium dichromate solution was used to seal the surface of oxide films to further improve the anticorrosion property. The oxide films sealed with potassium dichromate were covered with leaf-like structures resulting in larger corrosion resistance that attributed directly to the decrease of corrosion current.

Weatherability of Arc Thermal Spray Al-Mg Coating in a Simulated Marine Environment

Anticorrosion property of Al-5mass%Mg sprayed coating was evaluated by an atmospheric exposure test simulating marine environment for one-year. The test simulating marine environment means an accelerated exposure test where artificial seawater is sprayed on the coating surface in a general atmospheric exposure test. When the initial film thickness is small, the thickness of Al-Mg thermal spray coating decreased. For both exposure tests for one-year, the corrosion products of Al-Mg thermal spray could not be identified. From the results of EPMA, after the one-year atmospheric exposure test, Cl originating from airborne salts in atmosphere or from sprayed artificial seawater was not observed in the surface or inside of the Al-Mg coating. The spontaneous potential of Al-Mg thermal spray coating shifted to the noble side from that of the initial material after the one-year atmospheric exposure test. The anode polarization exhibited the same behavior in the two kinds of atmospheric exposure tests.