Abstract
Using the same specimens and solutions as described in the previous report, the e.m.f.-versus time (for one week) of mild steel/Al or Al alloy cells in various aqueous solutions at 60°C was investigated.
In hot tap water, every Al or Al Alloy is temporarily nobler (cathodic) than steel at the instance of immersion, but again returns to the basic state (anodic) sooner or later and finally provides sacrificial protection to the steel. But when Al or Al alloy is nobler than the steel temporarily, the steel electrode surface is attacked more or less. In hot distilled water, it may be said that every Al or Al alloy does not become cathodic. In hot sodium chloride solution, every Al or Al alloy provides sacrificial protection to the steel, except in the case of commercial Al (98%) which shows temporary potential reversal in the M/1000 solution. In hot dilute sulphuric acid and aluminum sulphate solutions, even if Al or Al alloy is always anodic to the steel, the steel electrode is generally attacked because the solution temperature is high.
1) M. Tagaya & S Isa, Jour. Metal Finishing Soc. of Japan, 10, 441 (1959)
