A sensitive and nondestructive optical reflectance technique has been developed to observe the quality of anodic film formed on aluminum. To interpret the reflectance spectra, Al2O3 vibrational modes and the optical constants associated with these modes were used.
Transmission electron microscopy,1 secondary ion mass spectrometry, and energy dispersive X-ray analyses2 have provided greater resolution of film composition and morphology. Two types of films have been detected: (1) barrier and (2) porous films.3
The purpose of this technical note is to present a nondestructive and sensitive optical reflectance technique for observing the growth and composition of the anodic films on aluminum, which in principle can be related to the variation of film structure. Another purpose is to determine the amount of ad-anions incorporated in the anodic film.
Aluminum was mechanically polished and then anodized at constant potential in various concentrations of phosphoric or sulfuric acid...
