The special-shaped blackened bolt is a specialized fastener designed to meet the connection requirements of power tower equipment. With its non-standard structural design and blackened surface treatment, it plays a critical connecting role in power transmission infrastructure.

Its "special-shaped" characteristic is reflected in its customized structure—tailored to the stress characteristics of different connection points on the tower (such as the tower leg and foundation, crossarm and tower body). It features unique head designs (such as hexagonal with tenon or square countersunk heads), non-standard pitch, or extended shanks to ensure precise matching with tower components, avoiding the risk of connection loosening due to dimensional mismatches common with generic bolts.

The "blackening" treatment involves chemical oxidation (commonly alkaline oxidation) to form a black oxide film (primarily composed of magnetite, Fe?O?) on the bolt surface. This enhances surface hardness, improving the bolt's wear resistance in outdoor environments with wind, sand, and rain. It also seals microscopic pores on the metal surface, blocking air and moisture from contacting the base material, significantly reducing the risk of corrosion during long-term outdoor operation of the tower and extending the bolt's service life.

These bolts must meet the high-strength standards of the power industry (typically Grade 8.8 or higher), capable of withstanding loads from the tower's self-weight, cable tension, and harsh conditions such as strong winds and ice accumulation. They ensure the structural stability of power towers and serve as essential components for the safe transmission of electricity in power systems.