IP67 vs IP68 For Vehicle And Marine Lighting

What The Digits Mean

In an IP rating the first digit covers solid ingress and the second covers water. A 6 in the first position means dust tight. In the second position, 7 means temporary immersion under defined test conditions, and 8 means continuous immersion at conditions agreed with the manufacturer. That last phrase matters: IP68 is not a single fixed depth, it is a rating against stated conditions.

Why IP67 Is Enough On A Road Vehicle

A lamp on a bumper sees rain, spray, a pressure washer and the occasional water crossing. Those are temporary immersion events, which is exactly what IP67 describes. Specifying IP68 for a bumper lamp adds cost without adding service life, because the failure mode on a road vehicle is vibration and thermal cycling, not standing water.

Why IP68 Is Mandatory Below The Waterline

A hull fitting is immersed permanently, and there is no drying cycle. Under those conditions an IP67 seal will eventually pass moisture, and once water is inside a sealed housing it has no way out. Any position that stays wet needs IP68 and needs the cable termination sealed inside the hull as well, because moisture will wick along the cable core into the lamp.

What The Rating Does Not Tell You

An IP rating is a water and dust test. It says nothing about salt water corrosion, galvanic action between a fastener and a hull, ultraviolet degradation of a lens, or whether a seal will take a compression set after three seasons. For marine use those factors decide service life more often than the IP number does, which is why fastener and housing material are worth asking about.

Practical Specification Rules

Above the waterline and on road vehicles, IP67 is the sensible default. Immersed, below the waterline, or permanently wet, specify IP68. In lockers, bilges and awning rails, use silicone coated strip rather than uncoated. Whatever the rating, seal the cable termination, because that is where water usually gets in.