H. J. Greene

Bio: H. J. Greene is an academic researcher from United States Department of the Army. The author has contributed to research in topics: Corrosion & Metal matrix composite. The author has an hindex of 1, co-authored 1 publications receiving 42 citations.

Corrosion Protection of Aluminum Metal-Matrix Composites

Abstract: Corrosion protection of aluminum metal-matrix composites (MMC) by anodizing treatments was investigated Electrochemical behavior of MMC without protection also was investigated Electroch

Corrosion protection of aluminum composites by silicate/cerate conversion coating

Abstract: The effect of silicate surface treatments on the corrosion inhibition characteristics of AA6061 T6-10% Al2O3 composite were studied in 3.5% NaCl. A series of specimens was carried out at different silicate concentrations using different application methods alone or combined with a sealing step in cerium solutions. The effect of surface etching and oxide thickening were also studied. Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion behavior of treated and untreated specimens. The pitting corrosion behavior and the perfect passivity domain were measured using potentiodynamic tests. The occurrence of localized corrosion due to chloride ion attack was examined by optical microscopy and SEM. Generally, silica/ceria treatments improve the corrosion resistance due to the formation of protective oxide films which act as a barrier to oxygen diffusion to the metal surface. Ceria sealing specimens showed a superior corrosion resistance indicating that cerate and not silicates plays the main part in the passivation mechanism. According to the EIS results, the etching process has a negative effect on the corrosion resistance.

Corrosion protection of an Al 6092/SiCP metal matrix composite

Abstract: The corrosion resistance of an Al 6092/SiC P metal matrix composite (MMC) has been evaluated by recording of impedance spectra during immersion in 0.5 N NaCl for at least one week. Various methods of corrosion protection have been applied. These included surface modification in the CeMo process and anodizing in sulfuric acid. Anodized surfaces were sealed by immersion in hot water, cerium nitrate and two different dichromate solutions. Significant improvements of the corrosion resistance were only observed for the anodized surface with a dichromate seal.

Anti-corrosion film on 2024/SiC aluminum matrix composite fabricated by microarc oxidation in silicate electrolyte

Abstract: A corrosion-resistant ceramic film was prepared on the SiC reinforced aluminum matrix composite by microarc oxidation technique in silicate solution. The film with two layer structure consists of mullite, α-Al 2 O 3 , γ-Al 2 O 3 and amorphous SiO 2 . Analysis of microstructure and composition suggests that only a few SiC particles remain in the film close to the composite/film interface and most of SiC reinforcements have transformed into the oxides under plasma discharge sintering. By microarc oxidation treatment, the corrosion current density of 2024/SiC decreases almost four orders of magnitude. The corrosion resistance of the coated 2024/SiC composite was greatly improved because the SiC reinforcements had not disrupted the continuity of micoarc oxidation film.

Mechanical properties and corrosion behaviour of fly ash particles reinforced AA 2024 composites

Abstract: Composites are most promising materials of recent interest. Metal matrix composites (MMCs) possess significantly improved properties compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Hence, composites with fly ash as reinforcement are likely to over come thecost barrier for wide spread applications in automotive and small engine applications. In the present investigation, AA 2024 alloy – 2 to 10 wt% fly ash composites were made by stir casting route. Phase identification and structural characterization was carried out on fly ash by X-ray diffraction studies. Scanning electron microscopy and optical microscopy was used for microstructure analysis. The hardness, compression and pitting corrosion tests were carried out on all these alloy and composites. The SEM studies reveal that there was a uniform distribution of fly ash particles in the matrix phase and also very good bonding is exist between the matrix and reinforceme...

Corrosion characteristics of hybrid Al/SiCp/MgAl2O4 composites fabricated with fly ash and recycled aluminum

Abstract: The corrosion characteristics of Al/SiCp/spinel composites fabricated with SiCp, fly ash (FA) and recycled aluminum were experimentally assessed. For type A composites prepared with the alloy Al–8Si–15Mg (wt.%), the Mg2Si intermetallic precipitated during solidification acted as a microanode coupled to the matrix (in the presence of condensed humidity) and led to catastrophic localized corrosion. Although the potential attack of SiC by liquid aluminum was successfully avoided by the presence of SiO2 in the FA, Al4C3 was still formed due to the reaction of carbon in the FA with aluminum. For type B composites, processed with the alloy Al–3Si–15Mg (wt.%) and calcinated FA, the silicon content was low enough to avoid formation of Mg2Si. Moreover, chemical degradation by Al4C3 hydrolysis did not happen either because of the absence of carbon and the presence of SiO2. This explains the physical integrity of type B composites even after 11 months of exposure to humid environment.