Effect of continuous rotation evolutional control on the surface color of anodized Al-Mg alloys

Al-Mg alloys treated by continuous rotation evolutional control (CREO) were anodized and colored by means of AC electrolysis at 10 V in sulfate solutions of 303 K containing Cu, Sn, Ni or Co. The anodized Al-Mg alloys were colored rufous (Cu), yellow to gold (Sn), or red brown (Ni and Co) by the electrolysis. The lightness of the colored Al-Mg alloys was significantly enhanced by CREO, regardless of the metals deposited. The gloss of the Al-Mg alloys decreased-probably due to an increase in surface waviness resulting from CREO. The enhancement of the lightness of colored Al-Mg alloys treated by CREO is attributed to the decrease in the glossiness. SEM images showed that the density of the micro-pores in anodic oxide films on Al-Mg alloys decreased as a result of CREO. The decrease in the density of the micro-pores may be assumed to have enhanced the lightness of the colored Al-Mg alloys treated by CREO.