Common methods of electroplating of die-cast aluminum parts

by:Zeyi     2021-06-21
The electroplating of die-cast aluminum parts is affected by the special properties of aluminum and requires special pre-treatments, and these pre-treatments need to be adjusted due to different aluminum materials and different parts, and general processes cannot be simply used. Therefore, for the workers engaged in the electroplating of die-cast aluminum parts, it is sometimes necessary to test the electroplating pretreatment of die-cast aluminum parts. To carry out this kind of experiment, the first step is the selection of pretreatment process and the design of improved methods. The electroplating pretreatment of die-casting aluminum/aluminum alloy die-casting includes four important processes: degreasing, acid etching, chemical plating or displacement plating, and pre-plating. The key is electroless plating or displacement plating. Therefore, the tests that are often done are focused on this process. Of course, different aluminum materials and different processing methods have different requirements for pretreatment. For example, the pretreatment of die-cast aluminum parts and rolled aluminum parts is very different, and even if it is the same processing method, different aluminum materials have different requirements. The pre-treatment process of aluminum, such as the amount of copper in aluminum, directly affects the bonding force of its coating. The test of the pre-treatment scheme for the electroplating of die-cast aluminum parts is also a systematic comparison test, and different samples need to be selected The pre-treatment process is processed, and then the same electroplating process is performed, and then the binding force is tested. The point of this comparative test is to ensure that all processes are under the same conditions except for the different process points, otherwise there will be no comparability and no evaluation can be made. There are four common methods for electroplating of die-cast aluminum parts: Aluminum phosphating has been studied in detail by using SEM, XRD, potential-time curve, film weight change and other methods. The influence of aluminum phosphating process. Studies have shown that guanidine nitrate has the characteristics of good water solubility, low dosage, and rapid film formation. It is an effective accelerator for aluminum phosphating: fluoride can promote film formation, increase film weight, and refine grain; Mn2+ and Ni2+ can be obvious Refine the grains to make the phosphating film uniform and compact and improve the appearance of the phosphating film; when the Zn2+ concentration is low, the film cannot be formed or the film formation is poor. As the Zn2+ concentration increases, the film weight increases and the O4 content increases the weight of the phosphate film. The impact is greater, increase PO4. The content increases the weight of the phosphating film. The alkaline electrolytic polishing process of aluminum has carried out research on the alkaline polishing solution system, and compared the effects of corrosion inhibitors, viscosity agents, etc. on the polishing effect, and successfully obtained an alkaline solution system with good polishing effects for zinc aluminum die castings, and For the first time, an additive that can reduce the operating temperature, extend the service life of the solution, and improve the polishing effect. The experimental results show that adding appropriate additives to the NaOH solution can produce a good polishing effect. Exploratory experiments also found that: NaOH with glucose After the solution is subjected to DC constant voltage electrolytic polishing under certain conditions, the reflectivity of the aluminum surface can reach 90%, but due to the unstable factors in the experiment, further research is needed. The use of DC pulse electrolytic polishing method under alkaline conditions is explored The feasibility of polishing aluminum, the results show that the pulse electrolytic polishing method can achieve the leveling effect of DC constant voltage electrolytic polishing, but its leveling speed is slow. Electrochemical surface strengthening treatment of aluminum and its alloys. The process, performance, morphology, composition and structure of aluminum and its alloys in a neutral system are anodized and deposited to form a ceramic-like amorphous composite conversion coating. Membrane process and mechanism. The process research results show that in the Na_2WO_4 neutral mixing system, the concentration of the film-forming accelerator is controlled to be 2.5-3.0g/l, the concentration of the complexing film agent is 1.5-3.0g/l, and the concentration of Na_2WO_4 is 0.5-0.8 g/l, the peak current density is 6-12A/dm-2, weak agitation, a complete and uniform gray series inorganic non-metallic film with good gloss can be obtained. The thickness of the film is 5-10μm, the microhardness is 300-540HV, and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloys, and can form a good film on various series of aluminum alloys such as rust-proof aluminum and forged aluminum. ————The article comes from the Internet. If there is any infringement, please contact to delete it.
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