How to Prevent Corrosion in Underwater Thrusters

Corrosion is one of the most common causes of performance loss and failure in underwater thrusters. Whether used in ROVs, AUVs, marine robots, or underwater inspection systems, prolonged exposure to water—especially seawater—can significantly shorten the service life of underwater thrusters if corrosion is not properly managed.

In this article, we explain why corrosion occurs, which components are most vulnerable, and practical methods to prevent corrosion in underwater thrusters, helping you improve reliability and reduce maintenance costs.

Why Corrosion Occurs in Underwater Thrusters

Underwater thrusters operate in a harsh environment where multiple factors accelerate corrosion:

• Saltwater exposure (high chloride content)

• Electrochemical reactions between dissimilar metals

• Water ingress caused by seal failure

• Long-term immersion and temperature variation

• Electrical current leakage in underwater systems

Saltwater corrosion is particularly aggressive and can quickly damage metal housings, shafts, fasteners, and electrical connections if not properly protected. This is why professional-grade solutions such as APISQUEEN U92 Pro underwater thrusters are specifically designed with corrosion resistance in mind for long-term marine use.

Components Most Affected by Corrosion

Understanding which parts are most vulnerable helps target prevention efforts:

• Motor housing and end caps

• Propeller and shaft

• Fasteners (screws, bolts)

• Shaft seals and bearings

• Electrical connectors and cables

Once corrosion starts, it can spread internally, leading to reduced thrust, increased power consumption, overheating, and eventual failure.

1. Choose Corrosion-Resistant Materials

Material selection is the first and most critical step in corrosion prevention.

Common corrosion-resistant materials used in high-quality underwater thrusters include:

• Marine-grade stainless steel (316/316L)

• Anodized aluminum alloys

• Engineering plastics (POM, Nylon, PPS)

• Titanium (for high-end applications)

Avoid mixing dissimilar metals where possible, as galvanic corrosion can occur when different metals are in electrical contact underwater.

2. Apply High-Quality Surface Treatments

Protective coatings significantly extend service life by isolating metal surfaces from water.

Effective surface treatments include:

• Hard anodizing (for aluminum housings)

• Anti-corrosion paint or epoxy coating

• Electrophoretic coating

• Passivation for stainless steel parts

For underwater thrusters used in seawater, coatings must be uniform and resistant to abrasion caused by sand or debris.

3. Ensure Reliable Waterproof Sealing

Corrosion often begins internally due to water ingress.

Key sealing elements include:

• O-rings (NBR, Viton, or silicone)

• Mechanical shaft seals

• Potting of cable exits

• Pressure-tested housing design

Even small leaks can allow moisture to enter the motor cavity, leading to corrosion of bearings, windings, and internal electronics. To reduce this risk, high-quality solutions like the APISQUEEN U92 Pro use fully sealed waterproof brushless motors engineered for long-term submersion.

Best practice: Always pressure-test underwater thrusters before deployment.

4. Prevent Galvanic Corrosion

Galvanic corrosion occurs when two dissimilar metals are electrically connected in water.

Prevention methods include:

• Using similar metals throughout the structure

• Adding insulating washers or sleeves

• Installing sacrificial anodes (zinc or aluminum)

• Ensuring proper grounding design

Sacrificial anodes corrode first, protecting critical thruster components.

5. Use Proper Electrical Protection

Electrical systems play a major role in corrosion acceleration.

Recommendations:

• Use marine-grade waterproof connectors

• Seal all solder joints with adhesive-lined heat shrink

• Avoid exposed copper conductors

• Match the ESC properly to the underwater motor

Electrical leakage in water can cause electrolysis, rapidly corroding metal components. Using reliable solutions such as the APISQUEEN U92 Pro with properly matched ESCs ensures both motor performance and longevity.

6. Rinse and Maintain After Use

Simple maintenance routines greatly reduce corrosion risk.

After each use—especially in seawater:

• Rinse the thruster thoroughly with fresh water

• Dry the unit completely

• Inspect seals, shafts, and fasteners

• Apply anti-corrosion spray or marine grease where appropriate

For long-term storage, store underwater thrusters in a dry, ventilated environment.

7. Choose a Thruster Designed for Marine Environments

Not all underwater thrusters are designed for long-term immersion.

A high-quality underwater thruster should feature:

• Fully sealed waterproof brushless motor

• Corrosion-resistant materials and coatings

• Reinforced cable exits

• Long-term submersion design (not splash-proof)

Professional-grade underwater thrusters, like the APISQUEEN U92 Pro, significantly reduce corrosion-related failures compared to hobby-grade products.

Conclusion

Preventing corrosion in underwater thrusters is essential for maintaining performance, reliability, and service life. By selecting corrosion-resistant materials, applying proper coatings, ensuring reliable sealing, and following good maintenance practices, corrosion risks can be dramatically reduced.

If your underwater application requires long-term stability and durability, investing in a well-designed underwater thruster—such as the APISQUEEN U92 Pro—is always more cost-effective than frequent replacements.