Strain Electrometry Studies of Aluminum

The potential of aluminum wires immersed in an electrolyte was followed after abrupt straining of 1.5-12%. The maximum potential achieved after straining in 0.1 M NaCl decreased with decrease in pH and the rate of decay to the initial steady-state value was independent of pH over the range of 1.5-6.5. The presence of dissolved oxygen in the solution increased the rate of decay to the steady-state value. The different potential behavior of untreated wires, wires heated in boiling water, and anodized wires was attributed to different mechanical properties of the oxide. The strain electrometry curves were identical in solutions of NaCl, Na2SO4, sodium tartrate, and Na2Cr2O7 of equal ionic strength. The pertinence of the results to the behavior of aluminum exposed at the tip of a growing stress corrosion crack is discussed.