Abstract
The pitting and protection potentials for pure aluminum in 0.5N NaCl solutions (pH=4, 6, 8, 10, and 12) were investigated by means of an apparatus consisting of a potentiostat and a high sensitive recorder.
The results obtained were as follows.
The pitting potentials determined by polarization curves of aluminum in 0.5N NaCl solutions (pH=4, 6, and 8) showed two kinds of different values.
(1) In the solution of pH=4, the 1st pitting potential was -1.15V (vs. S.C.E.) and the 2nd one was -0.73V (vs.S.C.E.); and the protection potential was -1.20V (vs.S.C.E.).
(2) In the solution of pH=6, the 1st pitting potential was -1.16V (vs.S.C.E.) and the 2nd one was -0.72V (vs.S.C.E.); and the protection potential was -1.20V (vs.S.C.E.).
(3) In the solution of pH=8, the 1st pitting potential was -1.16V (vs.S.C.E.) and the 2nd one was -0.70V (vs.S.C.E.); and the protection potential was -1.16V (vs.S.C.E).
(4) The pitting and protection potentials for aluminum in 0.5N NaCl solution (pH=10) were -0.70V (vs.S.C.E.) and -1.16V (vs.S.C.E.), respectively.
(5) The pitting and protection potentials for aluminum in 0.5N NaCl solution (pH=12) were -0.52V (vs.S.C.E.) and -1.89V (vs.S.C.E.), respectively.
