The hard chromium plating process is to deposit a thicker chromium coating on the surface of various substrates. Its thickness is generally above 20 μm. It uses the characteristics of chromium to improve the hardness, wear resistance, temperature resistance, corrosion resistance, and other properties of the parts.
Hard chromium plating is a traditional surface plating technology that has been used for more than 70 years. The chromium plating layer has high hardness, wear resistance, and corrosion resistance and can keep the surface bright for a long time. The process is relatively simple and the cost is low. For a long time, chromium plating has been widely used as a wear-resistant and corrosion-resistant coating for mechanical parts in addition to being a decorative coating. Electroplating hard chromium plating technology is often used to repair broken parts.
However, the hard chromium plating process will cause serious environmental problems. The chromic acid solution used in the chromium plating process will produce chromic acid mist and wastewater, and there are other shortcomings, such as the hardness is generally 800~900HV, which is harder than some ceramics and The cermet material is low, and the hardness will decrease as the temperature increases; the chromium plating layer has micro-cracks, which inevitably produce penetrating cracks, causing the corrosive medium to penetrate from the surface to the interface and corrode the matrix, causing rust spots or even peeling off on the surface of the coating; The deposition speed of the electroplating process is slow, and it often takes 2 to 3 shifts to plate a 0.2~0.3mm thick coating, which is not conducive to the application of thick coatings.
Therefore, the research field has been working hard to find new processes to replace hard chromium plating. Many new processes have emerged and have been applied and developed
A single layer of chromium plating has good corrosion resistance only when it reaches a considerable thickness. However, when the thickness of the chromium coating reaches more than 65 μm, increasing the thickness will not further improve its corrosion resistance. Generally speaking, the electroplating time has a great influence on the thickness of the hard chromium layer, and the selection of the electroplating time depends on the main salt concentration, temperature, current, and other process conditions of the plating bath.
In the actual electroplating production process, in order to accurately control the thickness of the chromium plating layer and improve the coating uniformity of cylindrical chromium-plated parts, cylindrical electroplating anodes are often used, and the alloy steel parts are regularly turned over and changed positions during the electroplating process. Ensure that the obtained hard chromium plating layer is uniform and detailed.
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