2 step coloring
2 step coloring process has been industrialized in the early 1960s and this is the way of coloring by electrochemically precipitating the metals into the micro-hole (150 - 200Å) of the anodic oxide film.
[Fig.1] Model diagram of 2 step coloring condition
Fine particles of nickel precipitated into the pores of sulfuric acid film
- Nickel was precipitated into the oxide film by Asada method under the following conditions; Sulfuric acid:180g/l, current density:1.5A/d㎡, temperature:20℃, time:40min
Picture magnification:x 320,000
(Literature) L.Sandera. Aluminium 49，533(1973)
(Offered by) L.Sandera(Swiss Aluminium Ltd.)
(Introduced by) Nobuyoshi Baba(Tokyo Metropolitan University)
Cross-section of the film electro-colored by nickel salt, after normal sulfuric acid film of 99.8% Al was intermediately processed in sulfuric acid bath for 15 minutes.(Offered by Kenji Wada of National Institute for Research in Inorganic Materials)
[Chart-1] Typical 2 step coloring process
|Summary||Typical method||Color tone|
|Anodic oxide film is electrolyzed by DC or AC in electrolysis bath containing metallic salts like Ni, Sn, Mn, etc.||At NACL, there are various methods such as
① H color, ② NK gray, ③ KN color.
|Stainless, Amber, Bronze, Black, Gray, etc.|