Reading the two digits
The first digit is solids, the second is liquids. For enclosures the interesting values are:
| Code | Solids | Liquids |
|---|---|---|
| IP54 | Dust protected (limited ingress) | Splashing water from any direction |
| IP65 | Dust tight | Water jets (6.3 mm nozzle, 12.5 L/min, 3 m, 3 min) |
| IP66 | Dust tight | Powerful jets (12.5 mm nozzle, 100 L/min, 3 m, 3 min) |
| IP67 | Dust tight | Immersion 1 m for 30 min |
| IP68 | Dust tight | Continuous immersion, depth and duration agreed with supplier |
| IP69K | Dust tight | High-pressure, high-temperature washdown |
A common mistake is treating IP67 as "better than IP66". They test different things: IP66 resists a powerful jet, IP67 resists still water. A washdown line wants IP66 or IP69K; a roadside cabinet wants IP67 and a vent.
Where sealed aluminum boxes actually leak
- Cable entries. A gland installed without its sealing washer, or into a hole with a burr, leaks immediately. Threads should be cut clean, the washer seated on bare metal, and the gland torqued to the manufacturer's figure.
- The end plate. A flat gasket between two machined faces needs even screw spacing. More than 60 mm between screws lets the plate bow and the seal lift.
- Screw holes. A through-hole with a screw and no seal is a capillary. Use blind tapped holes or sealing washers.
- Pressure cycling. A sealed box heated by its own electronics pressurises; when it cools it draws moist air in through the weakest seal. This is why a vent is often the difference between a design that passes a lab test and one that survives two winters.
- Condensation. Sealed does not mean dry. Moisture trapped at assembly condenses on the cold wall.
What we do for IP65 and IP67 housings
- Groove, not flat gasket. A machined groove with a moulded O-ring controls compression to 25–30% instead of relying on screw torque.
- Screw pitch. Maximum 50 mm between fasteners on a gasketed joint; 8 screws on a 150 mm end plate.
- Surface finish under the seal. Ra 1.6 or better on the sealing face; anodizing is masked off there, because an anodized layer is brittle and micro-cracked.
- Gland prep. Holes are deburred, threads cut to M12×1.5, M16×1.5, M20×1.5 or PG sizes, and a sealing washer is supplied.
- Vent option. A pre-tapped M12×1.5 position for an ePTFE vent plug on request.
- Immersion test. Sample units from each batch are immersed for 30 minutes with a tissue inside; any damp tissue fails the batch.
Choosing a rating without overpaying
| Application | Suggestion |
|---|---|
| Indoor instrument, clean factory | IP54 is enough |
| Outdoor pole-mounted sensor, rain and dust | IP65 minimum, IP67 preferred |
| Roadside / marine cabinet, occasional flooding | IP67 + membrane vent |
| Food processing, washdown | IP66 or IP69K, stainless hardware |
| Buried or continuously submerged | IP68, agree depth with supplier |
Each step up adds cost: seals, machining time, testing. Specifying IP68 for a device that lives under a roof is money you will never recover.
A quick specification note
Write the requirement like this in your RFQ:
IP67 per IEC 60529: dust tight, 30 min immersion at 1 m. Gasket in machined groove, anodizing masked at sealing faces. Two M12×1.5 gland entries with sealing washers, one M12×1.5 vent position. Immersion test report per batch.
That sentence removes almost all of the ambiguity that leads to failed first articles.
FAQ
Is IP67 waterproof enough for outdoor use?
IP67 covers 30 minutes at 1 m depth, which handles rain, splashes and temporary flooding. It does not cover steam jets, high-pressure washing or long-term submersion. For washdown areas use IP66/IP69K, for continuous immersion IP68 with the depth agreed with the manufacturer.
Do vents break the IP rating?
No. A breathable ePTFE membrane vent equalises pressure while blocking water to well beyond IP67. It actually improves reliability because it stops the gasket being stressed by pressure cycles.
Why does my IP67 box fog up inside?
Moisture was sealed in during assembly, or the box is breathing through a gland. Assemble in low-humidity conditions, add a desiccant packet, and fit a membrane vent so the housing can equalise without drawing water in.
Send us your housing spec
STEP or dimensioned PDF, target IP rating and annual volume. We answer with a price and a marked-up drawing — usually within one working day.