Abstract
Corrosion tests and measurements of anodic and cathodic polarization curves of aluminum were conducted in hydrochloric, sulfuric, nitric, and oxalic acids at pH=0 and 1. The results obtained were as follows:1) The values of corrosion rate at pH=0 in the acids used were as follows:In hydrochloric acid 77.1mdd (mg/dm2/day)In nitric acid 24.1mdd (mg/dm2/dayIn sulfuric acid 12.4mdd (mg/dm2/dayIn oxalic acid 6.2mdd (mg/dm2/day2) The values at pH=1 in the acids used were as follows:In hydrochloric acid 11.7mdd (mg/dm2/day)In nitric acid 7.0mdd (mg/dm2/dayIn sulfuric acid 7.0mdd (mg/dm2/dayIn oxalic acid 6.7mdd (mg/dm2/day3) The anodic polarization curve of aluminum in hydrochloric acid showed little polarization. The current was produced at a potential slightly nobler than the spontaneous electrode potential. Pitting corrosion was produced on the electrode.4) Limiting current appeared in the anodic polarization curves in the acids other than hydrochloric acid. It was due to the formation of oxide film on the surface of aluminum.5) Cathodic polarization curves were varied according to the quality of aluminum and kind of acids. The reason would be due to the electronic conductivity of the films on the surface of cathode.6) The corrosion current determined from the intersecting point of Tafel lines of anodic and cathodic polarization curves fairly corresponded with that calculated by the weight loss.
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