The uniformity of the passivation film is crucial for the corrosion resistance of metal surfaces in acid pickling and passivation processes. However, inconsistencies in the passivation film often occur, leading to localized corrosion during product use. This accelerates material degradation and significantly affects the product’s performance and lifespan.

Problem Analysis:

1. Inappropriate Pickling Solution Formula: Different metals require different pickling solutions, and failure to use the correct formula can result in uneven passivation film formation. This issue is particularly common when dealing with composite materials that involve multiple metals.

2. Improper Control of Process Parameters: If the process parameters—such as acid concentration, temperature, and treatment time—are not properly controlled, it can lead to inconsistencies in the thickness of the passivation film. This problem is especially pronounced when there are significant fluctuations in temperature or acid concentration.

3. Uneven Workpiece Placement and Immersion: The way workpieces are placed in the pickling bath and their immersion time can also affect the uniformity of the passivation film. Improper placement or incomplete immersion can result in poor passivation in certain areas, leading to an uneven film.

Solution:

1. Adjust and Optimize the Pickling Solution Formula: Tailor the pickling solution to the specific properties of different metals to ensure that the acid evenly affects the metal surface, resulting in a dense and uniform passivation film. When dealing with composite materials, consider using multi-functional pickling solutions or a stepwise treatment approach to ensure consistent passivation.

2. Precisely Control Process Parameters: Enhance control over the concentration, temperature, and treatment time of the pickling solution to ensure consistent process parameters for each batch. Implementing automated control systems to monitor and adjust these parameters in real time can help prevent the uneven formation of the passivation film due to process fluctuations.

3. Optimize Workpiece Placement and Immersion Techniques: Ensure that workpieces are properly placed to allow even contact with the pickling solution and that they are fully immersed. For complex-shaped or large-surface-area workpieces, consider using dynamic stirring or rotation systems to ensure even coverage by the acid solution.

By implementing these measures, the issue of uneven passivation films can be effectively addressed, enhancing the corrosion resistance of metal surfaces, ensuring product quality, and extending product lifespan, thereby improving market competitiveness.