Pinholes and pitting are common defects in the electroplating process, which affect the appearance, corrosion resistance and functionality of the coating. Eliminating these defects by optimizing process parameters is the key to improving electroplating quality.
Strictly control the concentration of each component in the electroplating solution. For example, too high a main salt concentration may lead to too fast a metal ion reduction rate, which is easy to produce pinholes and pitting. The main salt concentration should be accurately adjusted to the optimal range according to different electroplating systems and workpiece requirements. At the same time, the type and content of additives are also crucial. The right amount of brightener, leveling agent and other additives can improve the crystallization process of the coating and reduce the formation of pinholes and pitting. However, excessive or insufficient additives may cause problems and need to be optimized through experiments.
Current density is an important parameter affecting electroplating quality. Too high a current density will intensify the hydrogen evolution reaction on the cathode surface, and the generated hydrogen will be adsorbed on the cathode surface, hindering the deposition of metal ions, thereby forming pinholes and pitting. On the contrary, too low a current density will lead to too slow a deposition rate and low production efficiency. Therefore, it is necessary to determine the appropriate current density range according to factors such as the properties of the electroplating solution, the material and shape of the workpiece, and to make precise adjustments through methods such as the Hall cell test.
The electroplating temperature has a significant impact on the electroplating process. If the temperature is too low, the viscosity of the electroplating solution increases, the ion diffusion rate slows down, and it is easy to cause uneven coating, pinholes and pitting. If the temperature is too high, although it can increase the diffusion rate and deposition rate of ions, it may also cause the decomposition of additives to fail, and at the same time aggravate the hydrogen evolution reaction. Generally speaking, each electroplating process has its appropriate temperature range, and the electroplating temperature needs to be controlled within this range through a constant temperature device to obtain good coating quality.
Appropriate stirring can promote the diffusion of ions in the electroplating solution, make the ion concentration on the cathode surface evenly distributed, reduce concentration polarization, and thus reduce the probability of pinholes and pitting. However, if the stirring speed is too fast, the liquid flow on the cathode surface will be unstable, resulting in uneven adsorption of hydrogen on the cathode surface, which may increase the number of pinholes and pitting. Therefore, it is necessary to select the appropriate stirring mode and speed according to factors such as the size of the electroplating tank, the shape of the workpiece and the properties of the electroplating solution.
The pretreatment of the workpiece is crucial to the quality of electroplating. Thoroughly removing impurities such as oil, rust and scale on the surface of the workpiece can ensure a good combination between the coating and the substrate and reduce pinholes and pitting caused by surface uncleanliness. For example, chemical degreasing or electrochemical degreasing is performed using a suitable degreasing agent, rust and scale are removed by pickling, and sufficient water washing is performed after pretreatment to prevent residual impurities from entering the electroplating solution.
By optimizing process parameters such as electroplating solution composition, current density, electroplating temperature, stirring speed and pretreatment process, the occurrence of pinholes and pitting defects in the electroplating process can be effectively reduced, the quality and performance of the coating can be improved, and the high quality requirements of electroplated products in different industrial fields can be met.
