The corrosion characteristics of commercially pure aluminum immersed in ion-exchanged pure water containing a few ppm of various reagents were investigated under stagnant water conditions. Most of the tests were conducted at 35°C, but some of them were at 20° and 50°C for comparison. Increase of weight and loss of metal were measured as rates of corrosion and the relation between time and corrosion rates was determined.
Change in the composition of testing water had remarkable effects on corrosion. The dependence of these effects was greater on anion rather than cation in the water. The pH of water also had some effects, but they were dependent upon the kinds of anion even at the same value of pH. The effects of anion were divided into two groups. Anions of the 1st group produced general corrosion of aluminum similar to that in pure water. On the contrary, anions of the 2nd group more retarded the general corrosion with the increase in concentration.
The authors deduced a theory to explain these effects of anions. Although, pittings were hardly observed in these experiments and a hypothesis was presented to explain the effects of ions on the formation of pittings.
