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When it comes to dimensional accuracy, strength, and corrosion resistance, zinc die casting stands out among the other casting materials. Because of its high strength, even with thin-walled molded parts, and relatively good corrosion resistance when compared to other casting materials (especially when compared to other casting materials), this is especially true when compared to other casting materials. With this material, even the most complex geometries can be realized, making it ideal for use in architectural applications.
Zinc die-cast structural parts are used in a wide variety of applications and in many aspects of everyday life. These industries include the automotive, mechanical and apparatus engineering, electrical engineering and electronics, and construction industries, to name a few. A diverse range of processing methods must be applied to material in order to accommodate the diverse range of possible applications, with the methods varying depending on the area of application. When applied to parts, surface treatments of various types have different effects on their corrosion resistance, optical appearance, and tribological properties, depending on which type of surface treatment is used.
For the purpose of determining the most appropriate method for your requirements and preferences, the following are the most important factors to consider: 1.
Galvanic coatings with functional properties, such as zinc + passivation or direct passivation; Copper, nickel, and chrome galvanic coatings are examples of decorative galvanic coatings; and zinc + passivation or direct passivation are examples of functional galvanic coatings.
It is necessary to prepare the surface prior to painting it for this project, which will take several hours.
As shown in Fig. 2, decorative plating produces metallic surfaces that are stable and extremely uniform in appearance (as opposed to electroplating). In order to achieve this, Zinc alloy die casting are immersed in a series of different process baths, the end result of which is a decorative final layer of superior quality and gloss that is applied to the zinc die casting. The simplified representation of a typical layer sequence shown in Figure 3 is shown in the diagram.
The adhesion strength, leveling of roughness, and corrosion resistance of the first three layers of the sketched sequence are all achieved through the use of these layers. The remaining layers are used for a variety of other tasks. Only the fourth layer, which is the most subtle of the four, has a direct impact on the appearance of the surface, and it is also the most visible. Depending on the process used, the surface can have either a glossy or a matte appearance (see figure 4).
There are a variety of chrome plating methods available besides electroplating.
Chromium plating is applied as the final step, which increases the parts' abrasion resistance while also preventing them from forming nickel layers, which may result in nickel allergy. It also helps to maintain the parts' well-known metallic-blue color. It was previously only possible to use electrolytes that contained the element chromium (VI) as an active ingredient. Because chromic acid is toxic, it has been included in Annex XIV of the Reach Regulation, which is a part of the EU's Chemical Weapons Directive. As a result of their toxicity, chromium (VI) compounds have been included in Annex XIV of the Reach Regulation.
A long period of time has passed during which alternative methods have been researched and developed as a result of this. Using electrolytes that contain the element chromium (III), Zinc alloy die casting has also become possible in recent years to deposit chrome layers on surfaces. It is possible to achieve various optical characteristics, as illustrated in Fig. 5, depending on the application. For example, white type, dark type, anti-salt type, and others can all be achieved. The most frequently encountered optical characteristic is the white type.
The application of a functional coating to galvanizing improves the optical appearance of the metal.
It is possible to improve the appearance of the surface while simultaneously increasing the level of corrosion protection and corrosion resistance through the use of functional electrogalvanizing (see Fig. 6). A uniform zinc electrolytic deposit is formed on the component, and it can be used to create an even surface if necessary. As a result of the plating, the component appears more uniform and shinier as a result of the plating process. It is possible to achieve the desired appearance while also providing the necessary corrosion protection for the component by using the following chromium (III)-containing passivation:
There are two types of passivation available: passivation with a bluish iridescent thin film that provides moderate corrosion protection and passivation with a reddish-green iridescent thick film that provides excellent corrosion protection.
By using passivation in a dark color, it is possible to achieve excellent corrosion protection.
Increased corrosion protection, heat resistance, and tribological properties are all enhanced even further by the application of additional layers of coating.
Direct passivation of zinc die casting products can also be achieved through the use of chromium (III)-based processes, as previously stated. There are several advantages to using this method, the most important of which is the ease with which they can control the process and the low cost of doing so. In addition to the fact that the bath sequence and treatment times are significantly shorter when compared to galvanic plating followed by passivation, the throughput of material per batch can be increased significantly as well. This procedure does not produce any decorative properties, although it should be noted that it only produces a technical coating with excellent corrosion protection and does not produce any decorative properties in any way.
The adhesion of paint to metals that have been passivated with chromium (III) has been demonstrated. In addition, direct passivation provides an excellent foundation for subsequent painting applications to be applied on top of.
Because of the complicated geometry of the components, the excellent corrosion protection provided by the chromium (III) passivation becomes apparent when parts of the component are not painted or are only partially painted, either intentionally for reasons of dimensional accuracy or unintentionally due to the complicated geometry of the components, as is the case with the components under consideration.
When compared to the technique that preceded it, chrome (III) passivation is significantly more effective and efficient as a pre-treatment for painting than conventional iron phosphating, according to the results of this study. At the test scoring area, a distinct infiltration can be observed immediately following 120 hours of exposure to salt spray mist during the iron phosphating process. In the unpainted areas, extensive zinc corrosion can be seen, and even at the inner edges of the structure, which are not completely covered by the powder coating applied, it is possible to see that the corrosion has penetrated the coating and has gotten under the coating. The chromium (III) passivation, on the other hand, does not show any signs of infiltration as a result of the presence of chromium during the scoring of the test results. Except for these exceptions, areas that have not been coated or that have only been partially coated show little or no evidence of corrosion at all.