Corrosion characteristics of Al‐Si‐Mg/SiCp composites with varying Si/Mg molar ratio in neutral chloride solutions |
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Authors: | R Escalera‐Lozano M A Pech‐Canul M I Pech‐Canul P Quintana |
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Affiliation: | 1. Cinvestav Saltillo, Carr. Saltillo‐Mty Km 13, Saltillo Coah 25900 (Mexico);2. Departamento de Física Aplicada, Cinvestav‐Mérida. Km. 6 Antigua Carretera a Progreso Apdo. Postal 73, Cordemex. Mérida, Yuc. 97310 (Mexico) |
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Abstract: | The corrosion resistance of Al‐Mg‐Si/SiCp composites produced by the pressureless infiltration method using SiCp preforms with 50% porosity containing rice hull ash (RHA) and four custom‐made alloys with varying Si/Mg molar ratio] was evaluated in neutral 0.1 M NaCl solutions. The deleterious phase Al4C3 was successfully suppressed in composites with Si/Mg molar ratios of 0.89 and 1.05, but not in those with lower Si/Mg molar ratios (0.12 and 0.49). Results of cyclic polarizations in deareated 0.1 M NaCl solutions showed that with increasing Si/Mg molar ratio, passive current density increased but pitting susceptibility decreased both for reinforced and unreinforced alloys. Immersion tests in aerated 0.1 M NaCl showed that for composites with Si/Mg molar ratios of 0.12 and 0.49 chemical degradation by hydrolysis of Al4C3 was followed by intense anodic dissolution at the matrix–reinforcement interface, while composites corresponding to Si/Mg molar ratios of 0.89 and 1.05 did not exhibit intense localized attack. Possible reasons for the improvement in resistance to localized corrosion are discussed. |
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Keywords: | Al/SiCp composites anodic polarization cyclic polarization open circuit potential passive current density pitting potential pressureless infiltration protection potential rice‐hull‐ash Si/Mg molar ratio |
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