The influence of plating pre-treatment and the pre-plating process on the coating bonding strength of zinc alloy die-casting parts is briefly described. This is one of the many factors that affect the coating bonding strength of zinc alloy die-casting parts. The electroplating process method is just one of the many factors. Die-casting parts made of zinc alloy have seen widespread use in the manufacturing of other parts due to the material's favorable die-casting forming performance, low material consumption during the processing of forming, and high production efficiency. Surface treatments such as electroplating are frequently required in order to fulfill a product's specifications regarding China die casting mold its resistance to corrosion and any other decorative properties that may be affected by the surrounding environment. In zinc alloy electroplating, this is also the primary reason for the generation of scrap as well as products that have been modified.
There are a number of factors that influence the coating adhesion of zinc alloy die castings, and one of those factors is the influence of process methods on coating adhesion. The electroplating process, on the other hand, is a little more complicated. Electroplating zinc alloy die castings typically follows the sequence of steps outlined in the following paragraph: electrochemical degreasing; hot water washing; cold water washing; corrosion; cold water washing; activation treatment; pre-plating; cold water washing; after plating; cold water washing. The pre-plating treatment and the pre-plating process are the primary and most important factors that determine whether or not good coating adhesion can be obtained. This is true even though each step of the process has some degree of influence on the quality of the electroplating that is produced. On the other hand, for zinc alloy die castings, an additional important reason is due to improper selection and operation of the corrosion process before plating. This is a cause that is frequently overlooked. Because the metal is heated up during the die-casting process of zinc alloy die-casting parts, experience has shown that a relatively dense oxide layer forms on the surface of the workpiece. This is due to the fact that the metal is heated up. The coating's high-quality status cannot be guaranteed until such time as this condition is met. For the treatment of corrosion, a mixture of 1% to 3% hydrofluoric acid and 3% to 5% sulfuric acid is typically used, while the bonding strength is typically between 2% and 3% hydrofluoric acid.
Both of these processes are able to cleanly remove the oxide layer. Yuge discovered through production practice that the chemical reaction between the two corrosive liquids listed above and the zinc alloy is fairly powerful, and that the time control requirements for corrosion treatment while the machine is operating are stringent. If the time allotted is not long enough, the oxide film will not be able to be removed completely, which will result in plating. Poor bonding; if the time is extended, the dense layer on the surface of the base metal will corrode, exposing the loose layer that lies underneath the dense layer, and causing the corrosive liquid to penetrate into the pores of the loose layer, which will affect the subsequent pre-plating and electroplating processes. Poor bonding; if the time is extended, the dense layer on the surface of the base metal will corrode. This is the unfortunate result that occurs as a direct result of the corrosion process being ignored so frequently.
There is no need to state the obvious when it comes to the significance of electrochemical degreasing as a factor affecting the bonding strength of the coating before plating. For this reason, solutions with a low concentration and an average temperature should be utilized. In order to ensure that the coating has sufficient bonding strength, the metal will be corroded.
In the electroplating process for zinc alloy die-casting parts, the pre-plating process is one of the processes that takes place. It is an essential and fundamental step in the electroplating process of zinc alloy die-casting parts in order to obtain a barrier layer that prevents corrosion of the base metal during electroplating of the intermediate layer or surface coating.
When conducting the pre-plating process, it is recommended that a neutral electrolyte be used because this type of electrolyte is less corrosive to zinc alloys. An example of this would be neutral citrate nickel plating. In order to lessen the coating's stress and increase its toughness, organic additives should not be included in the electrolyte, or at least only a very small amount should be included. The value of the solution's pH should be kept within the range of 6. 2 under strict control. When the pH value is too low, the plating solution has poor dispersion ability; as a result, it is difficult to deposit a nickel layer in a short amount of time in the low current density area of the workpiece, or the nickel layer is too thin; alternatively, the nickel layer is too thin. If the pH value is too high, there is a greater chance that nickel hydroxide will be generated in the cathode area, and the pre-plating layer is more likely to have slag inclusions, roughness, and loose phenomenon. The intermediate coating or surface coating that is deposited on this surface is very prone to blistering and falling off.
In addition, the pre-plating solution's main salt concentration must not be too low or the process will not be successful. Because of this, the base body of the electroplating middle layer or surface layer might corrode, which could lead to other issues. Additionally, the plating layer might peel off. When copper cyanide is used as zinc alloy die casting supplier the base layer for the plating process. Pre-plating is necessary, however, as a result of the excellent dispersion ability of the copper cyanide electrolyte. It is possible to electroplate all of the components of the work in a relatively short amount of time with a thick layer of copper, which will prevent the base metal from corroding in the electrolyte during subsequent electroplating processes.
