Titanium Fasteners For Marine

The marine environment is recognized as one of the world’s most demanding corrosion environments, characterized by multiple corrosive factors, including high salt spray, strong tidal impacts, microbial attachment, and temperature fluctuations. Fasteners, core structural components in marine engineering projects such as ships, offshore platforms, submarine pipelines, and tidal power generation equipment, are subject to long-term corrosion from corrosive media and dynamic loads. Titanium is an ideal material for marine fasteners due to its extremely low marine corrosion rate (annual corrosion rate in seawater is less than 0.001mm), excellent strength-to-weight ratio (strength comparable to steel at only 57% of steel’s weight), and excellent fatigue resistance. With over a decade of experience in the research and development and manufacturing of titanium fasteners, Wstitanium has a precise understanding of the unique fastener requirements of marine engineering and has established a comprehensive core technology system, from material customization to finished product delivery.

Manufacturing Marine Titanium Fasteners

Marine titanium fasteners must simultaneously meet the four key requirements of “corrosion resistance, fatigue resistance, high precision, and strong adaptability.” Wstitanium has developed a targeted technology matrix centered around CNC precision machining, customized heat treatment, and marine-specific surface treatment.

CNC Precision Machining

Wstitanium has invested in high-precision 5-axis CNC machining centers and CNC thread grinders. These machines boast positioning accuracy of ±0.002mm and repeatability of ±0.001mm, enabling precise machining of bolts, nuts, washers, and other fasteners from M4 to M120. For extra-long stud bolts used on offshore platforms (up to 5000mm in length), a segmented machining process combined with overall straightening is employed. The dual spindles of a dedicated CNC lathe are driven synchronously to avoid machining chatter caused by excessive aspect ratios, ensuring bolt straightness errors of ≤0.1mm/m.

Heat Treatment

Marine titanium fasteners must withstand dynamic loads such as wave impact and equipment vibration. Their mechanical properties (particularly fatigue strength and toughness) directly determine structural safety. Wstitanium has developed a variety of customized heat treatment processes tailored to the load characteristics of different marine zones (splash zone, tidal range zone, fully immersed zone, and submerged zone) to achieve a precise balance of strength and toughness.

1. Stress Relief Annealing

This technology is primarily used to eliminate internal stresses generated during CNC machining, preventing stress concentration-induced stress corrosion cracking in fasteners in the marine environment.

2. Solution Aging

For marine engineering components subject to high loads (such as offshore platform leg bolts and ship propulsion system fasteners), Wstitanium utilizes a combined “solution + aging” heat treatment to enhance strength.

3. Low-Temperature Stabilization

For fasteners in fully immersed zones and submerged zones, where the risk of microbial corrosion and hydrogen embrittlement is higher, Wstitanium innovatively utilizes “low-temperature stabilization.” Maintaining the workpiece at 250-300°C for 10-12 hours promotes the formation of a dense TiO₂ oxide film on the surface, enhancing resistance to microbial corrosion. It also promotes the slow release of hydrogen absorbed within the material, reducing the hydrogen content to below 5ppm, effectively preventing hydrogen embrittlement.

Surface Treatment

In marine environments, salt spray, seawater immersion, and microbial attachment are the primary causes of corrosion failure in fasteners. Surface treatment is a key step in improving protective performance.

1. Pickling and Passivation

As a basic surface treatment process, its core goal is to remove machining scale, oil stains, and microscopic defects, forming a uniform passivation film. Wstitanium uses an environmentally friendly mixed pickling solution (HF:HNO₃:H₂O = 1:4:15) for immersion at room temperature for 8-12 minutes. The HF dissolves the oxide layer, while the HNO₃ forms a passivation film on the titanium surface, rapidly removing surface impurities. The product is then placed in a 50°C passivation bath (25% nitric acid solution) for 40 minutes, forming a dense TiO₂ passivation film 8-12nm thick. The surface roughness Ra is ≤ 0.8μm, and it can withstand 1500 hours of corrosion-free testing in a neutral salt spray test.

2. Micro-arc Oxidation

For fasteners in the splash zone (the most corrosive area), Wstitanium uses micro-arc oxidation technology to apply a ceramic coating. This technology uses titanium fasteners as anodes. High-voltage pulse discharges of 1000-1500V are applied in a silicate electrolyte, generating micro-arcing on the surface, forming a 50-100μm thick TiO₂ ceramic coating. The coating achieves a bond strength of ≥60MPa to the substrate and a hardness of HV800-1200. It exhibits excellent salt spray corrosion resistance (no red rust after a 5000-hour salt spray test) and excellent wear resistance, resisting wave impact and sand abrasion.

Wstitanium offers rapid customization capabilities, including hexagonal head bolts, flange bolts, stud bolts, lock nuts, spiral wound gaskets, set screws, and more. Available in sizes from M4 to M120 and lengths up to 6000mm, it is suitable for ships, offshore platforms, submarine pipelines, and more. In terms of structural customization, special structures are designed according to the connection characteristics of the equipment, such as nuts with anti-loosening teeth, flange bolts with sealing grooves, special-shaped gaskets, etc., to solve the compatibility problem between traditional fasteners and marine equipment.