ABSTRACT
Due to the importance of using AI as a protective layer on the surface of parts of automobile engine; the aluminon indicator was used as a selective spectrophotometric reagent for microdetermination of AI under optimum conditions in both Al-anodizing and Al-hard coat anodizing baths in HEIC at Helwan, Cairo. The effect of pH on the spectra of the AI- aluminon complex was studied at the acidic pH range similar to that of the anodizing baths and the most suitable pH for its microdetermination was found to be 4.0 at lambda[max] = 520 nm using 0.01 M indicator. Beer's Law was obeyed in the AI concentration range of 1 to 22.5 ppm with a percent recovery of 87 to 100.5 percent. The AI determined by this spectrophotometric method was found to be, in four corners of the first bath, 1.39 to 1.51 ppm 1[-1] and in the second bath 2.57 to 2.7 ppm ml[-1]; and at three depths 1.32 to 1.4 and 2.54 to 2.59 ppm ml"1 in both baths respectively. The f- and t-tests of the spectrophotometric results in comparison with the atomic absorption data gave a confidence level of 99.0 percent. The SD values of the AI results from six replicates in both baths were found to be in the range 0.037 to 0.479. These values show the reliability and reproducibility of these results. This procedure has been applied successfully for monitoring of AI concentration in anodizing baths of automotive engine parts made from Al-alloys at HEIC factory 99 in Egypt