The importance of airtightness

Achieving IP67/IP68 Waterproofing in Marine Aluminum Enclosures

Since we have addressed the challenges of heavy rain and high salt spray for marine equipment (like fishfinders and radar screens), the core technology lies in how to make aluminum alloy housings achieve submersible-grade waterproofing (IP67/IP68). At sea, this isn't just about rain; it’s about defending against high-pressure water jets and internal vacuum suction caused by temperature fluctuations.

1. Key Design Factors for Water-Tightness in Die-Cast Aluminum

The greatest advantage of aluminum die-casting over plastic is dimensional stability. Plastic housings often warp due to thermal expansion and contraction, leading to uneven pressure on the O-ring. Aluminum provides an extremely precise and rigid sealing surface.

A. Face Seal Design

This is the most common method for fishfinder front and back covers. A precise O-ring groove is cast or machined directly into the aluminum housing.

• Surface Roughness: The groove's roughness must be controlled between. If it’s too rough, water can seep through the metal grain; if it’s too smooth, the gasket may slip out of place.
• Compression Rate: Because aluminum is rigid, it can support a seal compression rate of 20% to 30%. This is difficult to achieve with plastic, which tends to "creep" or deform under such pressure.

2. Solving the "Breathing Effect": Protective Vents

This is the most overlooked cause of failure for marine radars and screens:

• The Scenario: During the day, direct sunlight heats the aluminum shell, causing internal air to expand. A sudden heavy rain or a cold wave then cools the shell rapidly, creating a strong internal vacuum.
• The Consequence: This vacuum sucks water droplets sitting near the seals directly into the device.
• The Solution: Install a waterproof breather vent (ePTFE Membrane) in a pre-threaded hole. It allows air to pass through to equalize pressure while completely blocking liquid water. The high thermal conductivity of aluminum works with the vent to quickly dissipate internal moisture.

3. Isolating "Dissimilar Metals" to Prevent Galvanic Corrosion

In a marine environment, if you secure an aluminum housing with stainless steel screws, you inadvertently create a "micro-battery" (Aluminum is the anode, Stainless Steel is the cathode).

• The Disaster: Within months, the aluminum around the screw holes will turn into white powder and crumble, causing the waterproof seal to fail.
• Engineering Countermeasures:
  1. Teflon-Coated Screws: Use screws with an insulating surface layer.
  2. Insulating Washers: Add nylon or rubber gaskets between the screw head and the aluminum body.
  3. Conversion Coating: Apply a high-quality "Trivalent Chromate" film after die-casting to break the electrical path.

4. Structural Layout for Fishfinders & Radars

When designing these products, I recommend splitting the aluminum housing into two parts:

• Front Frame: This holds the tempered glass. Use the high strength of aluminum to clamp the display panel tightly, ensuring the glass won't dislodge even when hit by massive waves.
• Rear Housing: Integrate large cooling fins. Radar processing chips generate significant heat; use thermal pads to transfer this heat directly to the aluminum shell, using the sea breeze for cooling.

Summary: The "Hard Power" of Aluminum at Sea

Learn more about Aluminum Die Casting Features

Browse Aluminum Die Casting Exhibits

Product development OEM consulting