Barrier layer thickness of aluminum, which had been subjected to corrosion tests in water containing a few ppm of various reagents, was determined by the polarization method proposed by M. S. Hunter and P. Fowle.
The thickness of barrier layer formed in the air decreased with increasing time of immersion in pure water up to 100hrs. The same behavior was also observed on aluminum tested in water containing any one of NaNO₃, NaCl, NaOH, and HCl. While, in water containing any one of NaF, Na₂SO₄, Na₂SiO₃, H₂SO₄, and H₃PO₄, the thickness of the layer formed in the air once decreased at the initial stage of immersion, and then, began to increase.
These results were compared with the corrosion rate of aluminum tested in the solutions mentioned above.
It was concluded that there was inverse correlation between the corrosion rate of aluminum and the barrier layer thickness after the tests in the various testing solutions for 100hrs. Further studies shall be made in future to reveal the reason of specific effects of anion in testing solutions on the barrier layer thickness of aluminum which was immersed in the solutions.