Corrosion characteristics of Al-Si-Mg/SiCp composites with varying Si/Mg molar ratio in neutral chloride solutions
✍ Scribed by R. Escalera-Lozano; M. A. Pech-Canul; M. I. Pech-Canul; P. Quintana
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- German
- Weight
- 493 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0947-5117
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✦ Synopsis
Abstract
The corrosion resistance of Al‐Mg‐Si/SiC~p~ composites produced by the pressureless infiltration method [using SiC~p~ 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 Al~4~C~3~ 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 Al~4~C~3~ 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.