Applications of Surtec 650 Passivation in the Aluminum Forging Industry

2026-05-21

In the aluminum forging industry, surface treatment technology directly affects a product’s corrosion resistance, surface quality, and the adhesion of subsequent coatings. Among these, Surtec 650 passivation technology—an eco-friendly, chromium-free process—is increasingly becoming a key alternative to traditional hexavalent chromium passivation.

I. Application Example: Corrosion Protection Requirements for Automotive Aluminum Forgings

An automotive manufacturer produces aluminum alloy suspension control arms. These parts are manufactured using aluminum forging processes and are exposed to complex environments (such as rain, salt spray, and sand) over extended periods. Without effective surface treatment, aluminum parts are prone to oxidation and corrosion, with corrosion issues being particularly severe in coastal regions or on roads treated with salt during winter.

Additionally, these parts require electrophoretic coating in subsequent processes. Improper surface treatment can lead to poor coating adhesion, resulting in issues such as blistering and peeling. Therefore, the company required a surface treatment solution that could provide excellent corrosion protection while remaining compatible with the coating process. In this context, Surtec 650 passivation technology emerged as the ideal choice.

II. Overview of Surtec 650 Passivation Technology

Surtec 650 is an environmentally friendly passivation process based on a trivalent chromium system (or a chromium-free system), primarily used for the surface treatment of aluminum and aluminum alloys. Its core function is to form a dense, uniform conversion coating on the aluminum surface, thereby enhancing the material’s corrosion resistance and coating adhesion.

This technology complies with environmental regulations such as RoHS and ELV and serves as one of the alternatives to traditional hexavalent chromium passivation. The following are the detailed technical specifications of Surtec 650:

1. Key Standards and Certifications

MIL-DTL-81706B:	Listed on the Qualified Parts List (QPL) (Type II, Class 1A, and Class 3).
MIL-DTL-5541F:	Meets and exceeds the corrosion resistance requirements of this standard.
Environmental Compliance:	Complies with RoHS and REACH standards and is completely free of hexavalent chromium.

2. Physical and Chemical Properties

Property	Specification Description
Appearance	Colorless to slightly iridescent (pale blue or pale brown), depending on the alloy composition
Coating Thickness	Typically less than 1 μm (approximately 0.2–0.5 μm)
Coating Weight	High-corrosion-resistant coating: approximately 0.25 g/m²; colorless coating: approximately 0.08 g/m²
Heat Resistance	Up to 100°C with minimal loss of corrosion resistance
Electrical Conductivity	Extremely low contact resistance, compliant with MIL standards (< 5000 μΩ/in²)

3. Performance Specifications

Corrosion Resistance (Neutral Salt Spray Test ISO 9227 / ASTM B-117):	Up to 336 hours in the bare film state (depending on the specific aluminum alloy grade; some grades can exceed 500 hours). Excellent resistance to filiform corrosion.
Adhesion:	Provides an excellent substrate for subsequent coating (spray painting, powder coating) or bonding.
EMC/EMI Performance:	Due to its good electrical conductivity, it is highly suitable for electronic enclosures requiring electromagnetic shielding.

SurTec 650 delivers outstanding performance in terms of heat resistance and electrical conductivity. Its excellent performance metrics—including corrosion resistance, adhesion, and electrical conductivity—make it ideally suited for the demanding operating environments described earlier.

III. Application Advantages in the Aluminum Forging Industry

1. Excellent Corrosion Resistance
The conversion coating formed after Surtec 650 treatment provides an effective barrier, significantly improving the corrosion resistance of aluminum forgings in salt spray environments and meeting the stringent requirements of industries such as automotive and aerospace.

2. Excellent Paint Adhesion
This passivation layer provides an ideal substrate for subsequent electrophoretic, spray, or powder coating processes, effectively enhancing coating adhesion and reducing coating defects.

3. High Process Adaptability
Suitable for aluminum forgings with complex geometries, including areas with deep holes and grooves, it ensures uniform treatment—a critical factor for forgings with intricate structures.

4. Environmental Compliance
Free of hexavalent chromium, it reduces hazards to the environment and operators, aligning with current trends in green manufacturing.

5. High Operational Stability
With a wide process window and low sensitivity to temperature, time, and concentration, it facilitates quality control in mass production.

Summary: In the aluminum forging industry, when parts are exposed to highly corrosive environments or require subsequent coating, Surtec 650 passivation technology offers an efficient, environmentally friendly, and reliable solution. By forming a stable conversion coating, it not only enhances product durability but also provides an excellent foundation for subsequent processes, making it one of the key development directions in modern aluminum surface treatment.