Accession Number : AD0716480

Title :   On the Chemistry of the Solution at the Tips of Stress-Corrosion Cracks in Aluminum Alloys.

Descriptive Note : Technical rept.,

Corporate Author : MARTIN MARIETTA CORP BALTIMORE MD RESEARCH INST FOR ADVANCED STUDIES

Personal Author(s) : Sedriks,A. J. ; Green,J. A. S. ; Novak,D. L.

Report Date : DEC 1970

Pagination or Media Count : 24

Abstract : 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 Al(OH)3. 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 Al(OH)3, and that the pH in this region can be calculated from the solubility product of freshly precipitated Al(OH)3. The study also suggests that similar conclusions apply to the stress-corrosion cracking of magnesium alloys. (Author)

Descriptors :   (*ALUMINUM ALLOYS, *STRESS CORROSION), SOLUTIONS(MIXTURES), CHEMICAL REACTIONS, HYDROXIDES, PH FACTOR, CHLORIDES, OXYGEN

Subject Categories : Physical Chemistry
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE