Tel:+86 (371) 6562-1391
Fax:+86 (371) 6562-1393
Aluminum oxidation of anodic oxidation with alkali and sand
1, anodic oxidation of the general principles
Aluminum or aluminum alloy article is an anode placed in the electrolyte solution , the use of electrolysis , so that the process of aluminum oxide film formed on the surface , known as aluminum and anodized aluminum . In which apparatus the electrolytic solution cathode material with a high chemical stability , such as lead , stainless steel, and aluminum. The principle of anodized aluminum is essentially the principle of water electrolysis . When the current through the cathode , the release of hydrogen ; the anode , the oxygen precipitate is not only a molecular oxygen , further comprising atomic oxygen (O) and oxygen ions , typically with molecular oxygen in the reaction expressed . As an anode on which the aluminum is oxidized by the oxygen precipitates , anhydrous aluminum oxide film is formed , not all of the oxygen generated with the aluminum effect , part of the precipitate in a gaseous form .
2, anodizing electrolyte solution choice
Anodic oxide growth is a prerequisite is that the electrolyte membrane due to oxidative dissolution . But this is not all that exists in the dissolution of the electrolyte can be anodized oxide film or an oxide film of the same nature generated .
3, anodizing type
Oxidation of chemical oxidation is generally ( not charged ) and anodizing ( energized ) , and usually anodized oxide . Anodizing : with aluminum as the anode , oxidation to form the surface layer of 5-20um Average oxide film , has good corrosion resistance and good wear resistance . Into the form by anodization current : DC anodizing, anodized AC , pulsed anodic oxidation. Divided by the electrolyte : sulfuric acid, oxalic acid, chromic acid, mixed acid and sulfo- acid -based solution to the natural colored anodic oxidation. Press temper of the film : ordinary film , the hard film ( thick film ) , ceramic film, a bright decorative layer , a semiconductor barrier layer effect anodization .
4 , anodizing Structure, Properties
Anodizing consists of two layers , the outer layer is thick porous dielectric having a dense inner layer grown up , which is known as the barrier layer ( also called active layer ) . Was observed with an electron microscope study , the vertical and horizontal surface of the film with the metal surface rendering almost all vertical tubular holes until they are outer membrane through the oxide film and a barrier layer of metal interface . For the spindle of each pore is surrounded by a dense alumina constitute a hexagonal honeycomb body , called the cell , the entire film is another such numerous cell components. The barrier layer is composed of alumina and water , thin and compact , has high hardness and blocking current through effect. The barrier thickness of about 0.03-0.05μm, the total membrane -2.0 % 0.5% . The outer porous oxide film is mainly alumina and amorphous alumina hydrate , and consisting of a small amount , in addition to containing the electrolyte cation. When the electrolyte is sulfuric acid , the sulphate content of the film under normal conditions , 13 % -17 % . Most of the oxide film is a porous outer layer of excellent characteristics of thickness and porosity are determined by feel , which are closely related with the anodic oxidation conditions .
6, alkali sand sandblasting oxidation and oxidative
Alkali sand oxidation : chemical etching method ( darker alkaline etching ) and then make a sand surface anodic oxidation effect , also known as matt anodized , alkaline etching the substrate after anodization , not shiny, general profiles processing this process , corrosion, insulation. Oxide sandblasting : sandblasting before making anodizing . Sandblasting is a physical effect, so that the aluminum surface is more delicate , can squeeze marks fade .
At present my company to use more common oxidation aluminum frame and base sand oxidation are two more expensive than ordinary alkaline oxidation oxidized sand expensive , customers can choose according to need .