How to Prevent Rust in Blackened Surface Treatment of Iron-Based Powder Metallurgy Parts?

Introduction

Iron-based powder metallurgy (PM) parts are prone to rust due to their iron content, especially in humid or high-temperature environments. Black oxide treatment is commonly used to improve surface corrosion resistance, but additional protective measures are essential for long-term durability. Based on extensive experience at MIMO, we have developed effective strategies to prevent rust in blackened PM parts.

1. Anti-Rust Strategies After Black Oxide Treatment

At MIMO, black oxide treatment provides a protective surface layer, but we have found that post-treatment processes play a crucial role in preventing rust.

• Applying Anti-Rust Coatings: After blackening, a thin layer of rust-preventive oil or lubricating oil is applied to create a protective barrier against moisture and oxidation. This is particularly effective in environments with high humidity or corrosive gases.

• Sealing Treatment: We use hot and cold sealing techniques to enhance the density of the black oxide film, reducing oxygen and moisture penetration. This significantly improves corrosion resistance and prevents rust formation over time.

2. Optimizing Process and Material Selection

The effectiveness of black oxide treatment is highly dependent on process parameters. At MIMO, we have optimized the following aspects:

• Strict Control of the Blackening Process: Using an alkaline blackening process with precise temperature and time adjustments ensures a uniform and adequately thick oxide layer, preventing corrosion issues caused by uneven coatings.

• High-Quality Powder Materials: We select alloy-treated iron-based powders with chromium and nickel additives, which inherently improve corrosion resistance and reduce rust susceptibility.

3. Environmental Control in Production and Storage

To maintain the effectiveness of the black oxide coating, we implement strict environmental controls:

• Regulating Humidity and Temperature: Fluctuations in temperature and humidity can degrade the oxide film. We optimize ventilation and drying systems in our facilities to prevent excessive exposure to moisture.

• Regular Maintenance and Re-Coating: For long-term protection, we apply periodic protective oil coatings and conduct routine cleaning to prevent surface damage and rust formation.

4. Strengthening Quality Control and Inspection

MIMO places great emphasis on quality assurance for blackened PM parts.

• Regular Quality Testing: We perform X-ray analysis, surface hardness tests, and microscopic inspections to detect any defects in the black oxide layer. Even minor cracks or inconsistencies can become rust initiation points, making routine inspections critical.

• Environmental Resistance Testing: We simulate different working conditions to evaluate the corrosion resistance of blackened PM parts, ensuring optimal performance in diverse environments.

Conclusion

MIMO’s approach to black oxide surface treatment for iron-based powder metallurgy parts combines precise process control, advanced material selection, effective protective coatings, and strict environmental management. By implementing these strategies, we significantly enhance the corrosion resistance and longevity of PM parts. These insights serve as valuable references for the industry, helping manufacturers maintain high-quality, rust-free components in challenging environments.