【China Aluminum Industry Net】 I. INTRODUCTION Electroplating various metals onto the surface of aluminum and its alloys can significantly enhance the physical and chemical properties of the material. When aluminum is used as a conductor, silver plating improves the electrical conductivity at contact points. To facilitate welding, copper, nickel, or tin coatings are often applied. For improved wear resistance, thicker layers are deposited. In terms of aesthetics, electroplated enamel is commonly used to enhance appearance. Although electroplating on aluminum and its alloys has been in practical use for many years, challenges remain. The presence of oxides between the metal and the coating, along with differences in thermal expansion coefficients, can lead to poor adhesion. Factors such as pinholes, residual plating solutions, and other imperfections may cause peeling or delamination over time. As a result, the electroplating process for aluminum and its alloys remains in an exploratory phase, with no major breakthroughs achieved so far. This has led to ongoing issues in quality control and product yield, making it a persistent challenge in the industry. II. Traditional Electroplating Process for Aluminum and Alloys In traditional electroplating, aluminum and its alloys can be coated in electrolytic solutions, but the adhesion of the coating is often weak and prone to peeling. One common approach is to first deposit zinc in an aqueous solution containing zinc oxide compounds, followed by electroplating—this method is known as zinc displacement or deposition. Another technique involves creating a thin porous oxide layer through anodizing before electroplating. 2.1 General Electroplating Process for Aluminum and Alloys The general electroplating process consists of three stages: pre-plating, electroplating, and post-plating. Pre-treatment is a critical step that determines the quality of the final product. Its main purpose is to remove oils, natural oxide films, and other contaminants from the surface of the aluminum alloy. A typical conventional process flow includes: degreasing, washing, deoxidation, washing, pickling, washing, activation, washing, primary zinc immersion, washing, zinc removal, washing, secondary zinc immersion, washing, neutral nickel plating, washing, and subsequent electroplating. Some processes also use an anodized film instead of the zinc immersion stage. 2.2 Drawbacks of the Traditional Pretreatment Process 1. The process flow is long and involves many steps. 2. The procedure is complex, with narrow operating ranges and strict control requirements. 3. The process is not universally applicable; different aluminum grades require different pretreatment methods. 4. Despite strict controls, the pass rate for decorative electroplating is only 85–90%, while functional electroplating ranges from 60–70%. 5. Each solution has a short service life and limited processing cycle. Due to these limitations, improvements to the traditional pretreatment process are necessary. III. Improved General Pretreatment Process for Aluminum and Alloys The new process includes: degreasing and caustic treatment in one step, washing, pickling, washing, deashing, washing, alkaline activation, zinc leaching, washing, neutral nickel plating, washing, and subsequent electroplating. IV. Practical Experience and Improvements This new process addresses the current shortcomings of aluminum alloy electroplating by leveraging the unique physical and chemical properties of the material. Key improvements include: 1. A shorter process flow, which enhances adhesion by selectively removing impurities from the surface. 2. Alkaline activation replaces acid activation, effectively eliminating residual silicon and silica gel. 3. After alkaline activation, direct zinc immersion avoids the formation of oxide layers during air exposure. 4. A single zinc immersion step provides better bond strength compared to multi-step cyanide-based processes. 5. The process is versatile and suitable for all types of aluminum alloys. 6. The one-time pass rate is significantly higher than traditional methods, reaching nearly 100% when bond strength is good. 7. The production process is simple and user-friendly. 8. Long-term automated production lines have proven the stability of this improved process. 9. It allows for easy upgrades based on traditional methods. 10. Using Haocheng aluminum oxidation power supplies can speed up film formation, reduce processing time, save resources, and improve cost-effectiveness.

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