1、Al、AlMg、AlMn Alloye、Greyfilm is more loosenH3PO4CrO3NaFH3BO355153Room temperature10-15Every Alumium Alloye、light greenfilm is better than 1Na2Cr2072H2O3.5-43-3.50.82-3Every Alumium Alloye、deep yellow or brownpH=1.5film is better43290-1003-5Al、AlMg、AlMn、AlSi、AlCu、greycan be the substrate of paint5Na2
2、CrO4Na2SiO39H2O470.06-1Al、AlMn、AlMgSi Harder、Harder AlSi or AlMg alloye,light metallic colorslittle holes, cant be colored well, unsuitable as the substrate of paint6NH4OH0.129.670-8020-50Every aluminum alloye、grey have spotfilm likes porcelain enamel7K2Cr2O720.410-18Every aluminum alloye、greywhite
3、in acid liquor2.1 General idea of anodic oxidation2.1.1、The principle of anodic oxidation filmPut the product that takes aluminum or aluminum alloy for anode into electrolyte. After electrolysis, oxidation aluminum will be formed on the surface. This kind of process is call anodic oxidation of alumi
4、num and aluminum alloy. In the whole process, the cathode should be the material which has good stability in electrolyte liquor, such as plumbum, stainless steel and aluminum etc. The principle of anodic oxidation of aluminum is the same as water electrolyte when the current through out, the hydroge
5、n will be released on the cathode while the oxygen will be released on the anodic. But the released oxygen is not only molecule oxygen, but also atom oxygen (O) and ion oxygen. We always use molecule oxygen to express. To oxidate the anodic aluminum by the oxygen it release, and then form anhydrous
6、oxidation aluminum film. Not all the released oxygen are reacted with aluminum, a part of it will be separated out as gaseity.2.1.2、The choice of anodic oxidation electrolyzing solutionThe precondition for the formation of anodic oxidation film is that electrolyte can dissolve the oxidation film, bu
7、t not all this kind of electrolyte can get oxidation film or similar film. Form-4 lists acidic electrolyte of which applies to anodic oxidation.Form-4 acidic electrolyte used in oxidationaciddissociation constantformed voltagecolor of basic filmH2SO4210-2(H+)12-20lucency & achromaticity30-40opacity
8、& whiteC7H6O6S40-70lucency with grayH2NSO2OHgray1.110-2(No1)7.510-8(No2)4.810-13(No3)lucency with whiteH4P2O71.410-1(No1)10-2(No2)2.910-7(No3)3.610-4(No4)70-100with white24Moo3P2O5XH2O100barrier layer6.410-100-600C2H2O46.56.110-5(No2)40-60with yellowC3H6N2O21.6110-3(No1)2.110-6(No2)80-110with brownH
9、OOCCH2COOH6.610-5(No1)2.8120change from white to yellowCis-2-Butenoic acid1.52.610-7(No2)150-225larkCitric acid8.41.84.010-6(No3)120 filemotTartaric acid6.9Benzene bicarbxylic acid1.263.1Itaconic acidPotted corrosion,40interferometer coatingHydroxyacetic acid1.5410-4Potted corrosionMalic acid410-4(N
10、o1)9Potted cossosion,402.1.3、 Kinds of anodic oxidationDivided by current: DC anodic oxidation, alternating current anodic oxidation, impulse current oxidation. Divided by electrolyte: vitriol, oxalic acid, chromate, mix-acid and the natural color anodic take for the sulfonic organic acid as main li
11、quor oxidation. Divided by film molecule: common film, film build, porcelain film, lucency film and prevent film used semiconductor. Form-5 introduces the common ways and crafts of anodic oxidation of aluminum and aluminum alloy. And the most popular one is DC sulphuric acid anodic oxidation.Form-5
12、common ways of anodic oxidation of aluminum and aluminum alloyseriesnamecomposing of electrolytedensity of currentA/dm2voltageVcolorthicknessof filmmAlumilite(USA)H2SO4,10%-20%DC 1-220-3010-30lucency5-30easy to color,corrosion resistantH2SO4 AC methodH2SO4,12%-15%AC 3-4.517-2813-2520-4010-25H2SO4 Ha
13、rd anodize fimeDC 2-4.523-1006034-150worn & heat insulationOxalic acidBritain-USA methodOxalic acid,5%-10%DC 1-1.550-6530translucencyOxidize aluminum fime(jp)AC 1-280-12020-2920-606-18daily used decorate, wornand corrosion resistantDC 0.5-125-30Eloxal Gxh(germang)Oxalic acid,3%-5%18-20yellowused in
14、pure aluminum30-4535almost achromaticity6-10thin, soft film, easy to colorEloxal Wx(germang)AC 2-325-35primrose yellowsuitable for aluminium wireEloxal WGx(germang)30-6015-306-20AlMn alloyHard fimeAC 1-2080-20020about 600m and thicker than vitriol film.wornDC 1-202.1.4、Strcuture and quality of anodi
15、c oxidation filmAnodic oxidation film is composed by two stories. The holey and thick out film formed upon the inside film which is thick and dielectric properties. The inside film is called prevent film (also called active film). Study by electron microscope, the film has many tube holes in length
16、and breadth. They through out the whole oxidation film. The principal axis around by holes is a six-edge beehive made by thick oxidation aluminum, and it is also called crystalloid cell. The whole film is formed by innumerable such crystalloid cells. Bar is formed by aluminum without water, thin and
17、 dense, and it also has high rigidity and can prevent the current through. Its thickness is about 0.03-0.05m, take 0.5%-2.0% of the whole film. Holey out film of the oxidation film is formed by non-crystalloid oxidation aluminum and little hydration oxidation aluminum, also some cation of electrolyt
18、e. When we use vitriol as electrolyte, the content of sulphate is 13%-17% on usual. Most of the excellent character of oxidation film depends on the thickness of out film and holey rate that has intimate relationship with conditions of anodic oxidation.2.2 DC vitriol anodic oxidation2.2.1、 Mechanism
19、 of oxidation film shapedThe surface of anodic aluminum products uniformity oxidates in short time, in vitriol liquor. And because of vitriol liquor, parts of the weak point of film (such as grain boundary, densed point of impurity, defect of cystal lattice and deformed of structure) dissolve can ma
20、ke self-metal touch with electrolyte and the current also can transmit on. Newly formed oxygen ion is used to oxidate new metal and spread the hole bottom as a center. After assembly, there will be a new film formed between the old film and metal. It seems like that parts of old dissolved film is pi
21、eced up again. With the oxidations time going on, the film dissolve and pieced up again and again, the oxidation developed in depth, thus oxidation film formed by thin and densed inside film, thick and holey out film will grow continually on the surface. It is until the end of oxidation the thicknes
22、s of inside film (prevent film, dielectric, active film) will not be changed, but the position will be moved in deep while the outside film get more and more thick.2.2.2、Calculation for the thickness of oxidation filmWe can calculate the thickness of oxidation film based on the formula of Faraday No
23、.2 law.= Kit presents the thickness of oxidation film ( m). i presents the density of current (A/dm2). t presents the time of oxidation (min). k is a coefficient (when the density of alumina =kg/m3, k=0.309). When we use the formula to calculate, the precondition is all the current through is used t
24、o separate alumina out, and the density should be thought of purify of alumina and film. But it is different with the fact. In order to make k more fit for actuality, we should also think of the efficiency of current and density of film and holey rate, that is:K = 1.57/ presents current efficiency (the rate of quantity separated out actually in electrode and separating quantity converted with the whole current). k is different in different countries. In the USA, k is 0.328,0.285-0.355, in Japanese, k is 0.352,0.364,0.25, in China and Russia, k is 0.25. 2.2.3、Element
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