Bleaching by Laser for Marking Black Anodized Aluminum

Irradiation by the beam from a CO2laser has been found to be an effective means of marking a black anodized aluminum surface. In general, this process works on any dark anodized surface. The beam is scanned over the surface to form a desired pattern. Depending on the circumstances, this technique could be an attractive alternative to painting, machine engraving, and etching; in particular, if there is a need to create a precise and/or intricate pattern, then this technique can satisfy that need in less time and at less cost while yielding better results. For this purpose, one uses a laser that is not powerful enough to cut the aluminum workpiece but is powerful enough to bleach the anodized surface to a nearly white appearance. The precise nature and degree of the bleaching depends on the specific aluminum-alloy/anodized-coating combination and on the parameters of the laser beam and scan. Tests at different laser power levels, scanning speeds, and numbers of pulses per unit length of scan must be performed on a sample of the particular anodized aluminum to find the combination of parameters that yields the best results.