On the Chemistry of the Solution at the Tips of Stress-Corrosion Cracks in Aluminum Alloys.
MARTIN MARIETTA CORP BALTIMORE MD RESEARCH INST FOR ADVANCED STUDIES
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A study was made of the factors affecting the change of pH with time of initially acidic pH 0 to 2 3 NaCl solutions, resulting from the dissolution of turnings of a commercial 7075 alloy, an Al-5.3 wt. pct. Zn-2.5 wt. pct. Mg alloy, and pure aluminum. It was shown that for solutions containing large volume fractions of the solids, a steady pH is attained which is associated with the onset of precipitation of AlOH3. It is suggested, by analogy, that the formation of the steady pH region at the tips of stress-corrosion cracks in aluminum alloys is also associated with the onset of precipitation of AlOH3, and that the pH in this region can be calculated from the solubility product of freshly precipitated AlOH3. The study also suggests that similar conclusions apply to the stress-corrosion cracking of magnesium alloys. Author
- Physical Chemistry
- Properties of Metals and Alloys