How is aluminum plate oxidized and colored? Is there any way to make aluminum oxide coloring? Under normal circumstances, there are two kinds of color on aluminum oxide board: artificial coloring and natural coloring. Artificial coloring can be divided into chemical coloring and electrolytic coloring. Natural coloring can be divided into Alloy Coloring and solution coloring. The aluminum plate manufacturer will give you an analysis and explanation one by one
The first case is chemical coloring: the oxidized aluminum material is immersed in organic or inorganic dye solution, and the dye penetrates into the pores of the oxide film, causing chemical or physical reaction and coloring. Chemical coloring equipment is simple, low cost, and many kinds of colors, but it has poor light resistance and corrosion resistance, so it is only suitable for interior decoration.
The second case is electrolytic coloring: after the oxidation of aluminum, in a single metal salt or a variety of metal salt solution, the secondary electrolysis, under the effect of electric field, metal cations penetrate into the pores of the oxide film, and deposit at the bottom of the hole, so that the oxide film produces bronze, brown, gray, red, green, blue and other colors.
The third case is natural coloring: Anodizing and coloring of aluminum. There are alloy coloring method and solution coloring method. Alloy coloring method is to control the composition of aluminum alloy to obtain different hues; solution coloring method, also known as electrolytic coloring method, is to control the composition of electrolyte and electrolytic conditions to control the hue. In practical production, organic acid is usually used as electrolyte for natural coloring, and a small amount of sulfuric acid is added to adjust pH.
In order to prolong the service life of the aluminum alloy products, the aluminum oxide layer with different color is applied. The basic process of oxidation coloring is aluminum surface treatment, oxidation, coloring and subsequent hydration sealing, organic coating and other treatment processes.
Under natural conditions, the surface of aluminum oxide keeps a layer of 10-100 angstrom oxide film, while the artificial oxide film is controlled within 0.5-250 μ m according to different purposes. There are chemical oxidation and electrochemical oxidation (i.e. anodic oxidation) methods for the formation of artificial membranes.
Chemical oxidation is the chemical reaction of surface purified aluminum or aluminum alloy in the oxidation solution containing oxidant and activator to form an oxide film. The role of the activator is to make the oxide film partially dissolved in the formation process, resulting in pores, so that the oxidation continues and the oxide film can be thickened. There are many kinds of oxidation solutions, usually using chromate as oxidant and carbonate as active agent.
Anodizing is usually carried out in electrolyte solutions such as sulfuric acid, oxalic acid or chromic acid. Under the action of direct current electric field, the anion (OH) moves to the anode, and produces new oxygen on the anode and reacts with aluminum as anode to form oxide film. In the electrolyte, the acid can partially dissolve the oxide film and produce pores, which makes the oxidation reaction develop in depth. This method can form porous structure on the surface of aluminum, which can be used for various coloring treatments and can be used as paint primer.