Visual Detection of Hydrated Aluminum Oxide by Staining with Fluorescing and Nonfluorescing Dyes

This new technique allows identification, location and distinction of hydrous aluminum oxide on bare untreated Al, phosphate-treated Al and barrier oxide produced in neutral aqueous phosphate or borate electrolytes or ammonium pentaborate in ethylene glycol. After the 99.99-99.97% pure annealed Al foil specimen has contacted pure water or water vapor, it is dipped into a dye solution, the excess removed with acetone, and then dabbed dry to avoid water condensation. Surface treatments prior to reaction had no effect on adsorption. Experimental parameters that influenced adsorption were temperature, solvent, dye concentration, p H and time. Advantages of fluorescent staining are that it is more sensitive and it can be located optically under electron bombardment. This technique has applications for Al capacitor foils and Al metallization in integrated circuits. 20 ref.--MAY.