Authored By: SDI Plastics

The maritime and marine industries operate in some of the most unforgiving environments on the planet. Saltwater corrosion, UV exposure, extreme pressure, and variable temperatures are constant challenges that demand materials of extraordinary durability, performance, and precision. For decades, metals have been the default choice for building and maintaining ships, submarines, buoys, offshore platforms, and marine equipment.

But today, there’s a quiet transformation taking place, and it’s being powered by plastic.

More specifically, injection moulding is enabling marine manufacturers to produce lightweight, corrosion-resistant, cost-effective, and highly durable components with speed and scalability. From custom housings for underwater sensors to boat fittings, impellers, and even entire floating structures, plastic injection moulding is now an integral part of the marine world.

In this blog, we’ll explore exactly how injection moulding supports the maritime and marine industry , from functionality and materials science to manufacturing strategy and environmental sustainability.

The basics: what is injection moulding?

Injection moulding is a manufacturing process that involves injecting molten thermoplastic (or thermoset) material into a custom-designed mould cavity under high pressure. Once cooled and solidified, the part is ejected , ready to use or further assembled.

Key advantages include:

• High repeatability and precision
• Complex geometries made cost-effective
• Fast cycle times for mass production
• Material versatility
• Minimal waste

These traits make injection moulding ideal for marine components, which often require complex shapes, structural strength, tight tolerances, and resistance to environmental stressors.

Where injection moulding fits in the marine sector

1. Boat & shipbuilding components

Plastic injection moulded parts are now found throughout vessels , both internal and external. These include:

• Dashboard enclosures
• Storage compartments and hatches
• Drain plugs, cleats, and fairleads
• Fuel caps and sensor mounts
• Helm panels and switch casings

Plastics offer critical resistance to UV radiation, corrosion, and saltwater , outperforming traditional metal parts that would otherwise require anti-corrosion coatings or regular replacement.

2. Buoyancy and flotation devices

Many maritime tools rely on buoyancy , whether it’s life-saving equipment, sonar floats, fishing buoys, or autonomous surface vehicles (ASVs). Plastics like polyethylene (PE) and polypropylene (PP) are widely injection moulded to create:

• Life jackets and lifebuoy casings
• Foam-filled floaters for mooring
• Buoyant bodies for AUVs and ROVs

These materials are not only lightweight and durable but also chemically inert, which is essential in preventing marine pollution.

3. Offshore oil & gas infrastructure

In harsh offshore environments, injection moulded plastics are increasingly used in:

• Cable protection and guides
• Sensor housings
• Valve handles and caps
• Pipe clamps and spacers

Engineering plastics like PEEK, nylon, or glass-filled polyamide provide outstanding performance under pressure, mechanical loads, and aggressive chemicals, reducing maintenance downtime.

4. Underwater equipment

Injection moulded plastic housings and accessories are used for:

• Underwater cameras
• ROV (Remotely Operated Vehicle) body panels
• Acoustic sensor casings
• Depth and pressure instruments

With custom moulding, marine engineers can achieve watertight enclosures and complex geometries without relying on expensive, corrosion-prone metal components.

5. Fishing and aquaculture

In aquaculture farms and fishing fleets, plastic parts now dominate:

• Net floats and cages
• Feeder system parts
• Fish bin lids and containers
• Fishing gear handles and mounts

These items benefit from lightweight mobility, low maintenance, and recyclability, aligning with the growing trend of sustainable seafood operations.

Material matters: marine-grade plastics in injection moulding

The choice of plastic is just as critical as the mould design in marine applications. Injection moulding companies serving the maritime sector often rely on:

Polypropylene (PP)

• Lightweight and water-repellent
• Chemically resistant
• Cost-effective

Used for: floats, bins, fittings

High-Density Polyethylene (HDPE)

• Strong and impact-resistant
• Great UV and chemical resistance

Used for: marine tanks, containers, buoy housings

Nylon (PA6, PA66)

• High tensile strength
• Wear resistant
• Good for mechanical parts

Used for: gears, bushings, cable ties

PEEK (Polyether Ether Ketone)

• Excellent heat and chemical resistance
• Ideal for demanding offshore and subsea parts

Used for: downhole tool components, seals, insulators

Polycarbonate (PC)

• Transparent, tough, UV-stable

Used for: instrument covers, light lenses

By using material-specific additives, such as UV stabilisers, anti-fouling agents, and flame retardants, injection moulded marine components can be further enhanced for long-term performance at sea.

Design benefits: why marine engineers prefer injection moulding

Precision fit and functionality

Custom-moulded parts can be designed to integrate perfectly with surrounding equipment, reducing vibrations, noise, and the risk of failure.

Lightweighting

Replacing metal parts with engineered plastics can reduce a vessel’s overall weight, directly improving fuel efficiency and cargo capacity.

Non-corrosive and chemically stable

No rust. No galvanic reactions. No repainting. This dramatically reduces long-term maintenance costs for both recreational and commercial fleets.

Reduced cost at scale

Once tooling is complete, high-volume production becomes highly economical , an advantage for OEM suppliers and marine product manufacturers.

Freedom of geometry

Complex 3D shapes, ribs, internal threads, snap fits, and aesthetic textures are all achievable , something difficult or expensive to do with machined metal or composite layups.

Environmental considerations: plastics and the blue economy

While plastics in the ocean have rightly drawn scrutiny, injection moulded plastics , when properly designed, used, and recycled, play a role in sustainable marine development.

Many companies are now using:

• Recycled plastics in non-critical components
• Biodegradable resins for single-use sea markers or packaging
• Modular plastic assemblies that can be dismantled and refurbished

Marine industries are also turning to localised manufacturing using custom moulding partners like SDI Plastics to reduce their carbon footprint from imports and transportation.

As the blue economy grows, innovation in plastic design and responsible manufacturing becomes a key part of balancing environmental stewardship with operational performance.

Partnering with injection moulding specialists

To develop successful marine-grade plastic components, collaboration with an experienced moulding company is critical , especially in areas like:

• Design for Manufacturability (DFM)
• Material selection guidance
• Tooling development and prototyping
• Quality control and compliance

Injection moulding for maritime applications isn’t just about parts , it’s about performance in the harshest of real-world environments. Every fitting, housing, or support structure must be engineered not only to meet mechanical specs but also to survive long-term exposure to the elements.

Final thoughts: future of plastics in the marine industry

As climate change drives demand for sustainable shipping, offshore energy, and marine research, plastics , when used responsibly , offer a powerful path forward. Injection moulding stands out as a key enabler of this future, blending efficiency with innovation.

From corrosion-free components to lightweight, modular infrastructure, the opportunities are immense. What matters is how they’re designed, produced, and deployed , with performance, longevity, and circularity in mind.

Looking to innovate for the marine industry?

If you’re exploring marine-grade plastic parts for your next project , whether it’s boating accessories, aquaculture gear, or offshore equipment, working with a trusted injection moulding partner is essential.

SDI Plastics, based in Brisbane, Australia, is a quality-assured injection moulding company with deep expertise in product design, custom tooling, and precision plastic engineering. From idea to prototype to production, their team helps bring durable, functional, and performance-driven plastic solutions to life, across industries, including the maritime sector.