Advances in chemical conversion film treatment on surfaces of aluminum and aluminum alloys

at a certain temperature, a thin layer of oxide film, called aluminum chemical oxidation, is generated on the surface of the aluminum part by chemical reactionThis method does not require the current, the process is simpler than electrochemical oxidation method, low costThe resulting oxide film is very thin, the general film thickness of about 0.5 to 4 m, the membrane layer is soft, wear resistance is very low, so can not be used alone, the membrane layer has better physical adsorption capacity, is a good bottom layer of paint, after chemical oxidation and then coating the protective layer, can greatly improve the protection capacity of parts2, anode oxidationaluminum alloy anode oxidation is made of aluminum or aluminum alloy, lead, carbon or stainless steel as a cathode, in oxalic acid, sulfuric acid, chromic acid and other aqueous solution electrolysisAnode oxidation by electric power can obtain the membrane velocity which is difficult to obtain by natural oxidationin the process of oxidation into membrane, two processes occur at the same time: one is the process of generating Al2O3 oxide film on the surface of the aluminum plate, and the process of oxidation film generation is accompanied by the process of oxidation film dissolutionOnly when the production speed of the oxide film exceeds its dissolution speed can a certain thickness of the oxide film, the thickness of the film is generally 5 to 15 mThe membrane is a double-layered structure consisting of dense obstruction layers and porous layers of a column structureanode oxide film can be divided into two main categories: porous type - a membrane generated in an acid electrolytic bath such as sulfuric acid, oxalic acid and forming a very fine hole perpendicular to the surface;3, microarc oxidationmicroarc oxidation, also known as plasma oxidation, is based on anode oxidation, in the metal base surface in situ growth ceramic layer of a surface treatment technologyIts basic performance and ceramic (corundum) similar, with a high hardness and wear resistance, high temperature resistance, but also has a high insulation and acid-base corrosion4, rare earth conversion filmat home and abroad in this area of research has made great progress, in which the development of rare earth passivation technology because of non-toxic non-pollution, good corrosion protection characteristics and much attentionAt present, the rare earth conversion membrane process can be divided into three categories:(1) chemical method containing strong oxidants and other film promoters ; Adding strong oxidants such as H2O2, KMnO4, (NH4) 2S2O4, etc can greatly reduce the processing time, solution treatment temperature is not high, strong oxidant chemical process containing low temperature short-term film is the most potential for development; 5, silicone treatment silanetreatment treatment traditionally uses the immersion process, aluminum alloy immersed in this thin silaneized solution for a certain period of time, and then cured at a certain temperature, can form a coating of several hundred nanometers thick on the surface of the aluminum alloy (much thinner than the traditional transformation coating), the coating can effectively prevent aluminum alloy in various forms of corrosion Hu Jiming and others used electrochemical techniques in the surface deposition of LY12 aluminum alloy was used by the dibase tri-methioline (DTMS) membrane Reflective absorption infrared spectra show that the DTMS silane reagent and the surface of the aluminum alloy have a chemical bond cooperation, the generation-SiOAl key to achieve membrane, electrochemical impedance spectrum (EIS) test results show that compared with the open potential, the use of cathode potential deposition method to obtain the corrosion resistance of silane membrane significantly improved 6, phosphating primer treatment phosphated substrate base material, componentone to polyethylene alcohol-based butalt resin, plus chromite and other anti-rust pigments and additives, components of two for phosphoric acid, before the use of the two parts according to the prescribed proportion of mixing uniform, sprayed on the surface of the aluminum plate part of the Phosphoric acid and metal aluminum combination, so that the metal surface and coating film into one, coating film has a certain degree of anti-corrosion capacity, but also with the coating system of the primer has a good binding capacity, but, phosphophosphated primer on the construction conditions required high, slightly careless, will cause the paint film brittle, resulting in large-scale paint removal of serious consequences