Pink Titanium Fasteners

Pink titanium fasteners are not simply a product of “colored titanium”; rather, they are high-end fasteners that combine functionality and decorative features, resulting from a titanium alloy undergoing a special surface treatment. Their pink appearance stems from the optical interference effect of the titanium oxide film on the surface, rather than traditional paint or plating. This creates a strong chemical bond between the color and the substrate, offering multiple properties including wear resistance, anti-fading, and enhanced corrosion resistance. With the increasing demand for “performance + aesthetics + personalization” in high-end manufacturing, pink titanium fasteners are finding increasing application in aviation interiors, high-end medical devices, luxury goods, precision electronics, and other fields.

Anodizing

The pink appearance and enhanced performance both rely on surface treatment. Currently, the mainstream technology is anodizing, which uses electrolysis to form an oxide film (TiO₂) of controlled thickness on the titanium surface. The thickness of the oxide film, along with the optical interference effect, determines the pink hue.

Pretreatment: Before anodizing, fasteners must be pickled, typically using a mixture of hydrofluoric acid and nitric acid (approximately 1:3 by volume). This removes surface scale and oil, exposing the titanium substrate and ensuring the bond between the oxide film and the substrate. The pickling time must be strictly controlled (generally 30-60 seconds) to avoid excessive corrosion and surface roughness.

Anodizing: The pretreated titanium fastener serves as the anode in an electrolyte (commonly used solutions of oxalic acid, sulfuric acid, or phosphoric acid, with a concentration of 5%-15%). A lead plate serves as the cathode. A DC voltage (10-60V) and a current (1-5A/dm²) are applied. The oxide film thickness (typically between 50-200nm) can be controlled by adjusting the voltage, current density, and electrolysis time. When the oxide film reaches a specific thickness range, light reflected and interfering upon its surface creates a pink appearance. For example, in an oxalic acid electrolyte, a voltage of 30V and an electrolysis time of 15 minutes produce a uniform, light-pink oxide film. Increasing the voltage to 45V thickens the film and deepens the pink hue.

Sealing: The oxide film produced by anodization has a microporous structure and requires sealing to improve corrosion and wear resistance. Hot water sealing (80-100°C deionized water for 20-30 minutes) is commonly used. This converts the TiO₂ in the oxide film into hydrated titanium dioxide (TiO₂・nH₂O), filling the micropores. The sealed oxide film achieves a hardness of 300-500 HV, and its pink appearance is more durable and resistant to fading.

In addition to anodizing, some high-end scenarios will use physical vapor deposition (PVD) to assist in coloring. By depositing a composite layer of titanium nitride (TiN) and an oxide film, precise control of the pink tone can be achieved, while further improving the surface hardness (reaching over 1000HV). However, this is relatively expensive and is mostly used in the fields of precision electronics or luxury goods.