Weatherproof Electrical Enclosures: Where the Water Actually Gets In
A weatherproof electrical enclosure fails at three places, and none of them is the weld. Water gets in at the door seal, at the cable entries, and through a flat roof that ponds. That is why we ask for the environment and the cable-entry layout before we quote an outdoor cabinet — the difference between an IP54 box and an IP66 box is a few drawn details, not a thicker gauge.
Fulei Metal builds outdoor-rated enclosures from customer drawings in mild steel, stainless 304/316 and aluminium, in Ningbo, China, since 2016. We do not sell a catalogue weatherproof box. We build the one that has to survive your site.
What “weatherproof” actually has to survive
| Site condition | What it does to the enclosure | What has to be in the design |
|---|---|---|
| Driving rain, any angle | Water is pushed past a flat-laid gasket | Compressed seal, drip edge, door overlap |
| Wind-driven dust | Fine dust passes gaskets and coats boards | IP65 minimum, positive pressure or filtered vent |
| UV and solar gain | Gasket hardens and shrinks; internal temperature rises | UV-stable gasket, shade roof, thermal path |
| Coastal or de-icing salt | Chloride pitting at welds and cut edges | Stainless 316, or 304 with sealed edges |
| Washdown (food, pharmaceutical) | Water forced past the seal by pressure | IP66 with a tested gasket design, no trap corners |
| Condensation cycle (day/night) | Internal water with no external leak | Breather drain, or a small controlled-pressure vent |
The three places water gets in
1. The door seal. A gasket laid flat in a channel and closed by a single latch compresses unevenly. The middle bows out and the corners stay open. The fix is drawn, not bought: enough latches to distribute compression, a seal that sits in a captured channel rather than glued to a flat face, and a door overlap that sheds water away from the seam.
2. The cable entries. Every hole through the wall is a leak path until it is sealed. Gland plates are the usual answer, but the plate itself becomes the problem if it is added as a flat patch — water tracks along the plate face and under the gasket. We build cable-entry plates as part of the wall, with a flange and a sealed joint, so the penetration is designed rather than patched.
3. The roof. A flat top is a puddle. Water sits, finds the lowest point of the seam, and gets in — or the roof heats in the sun and drives condensation inside. A sloped or domed roof with an overhang solves both, and it costs nothing extra at the folding stage.
IP rating: what the number does and does not promise
| Rating | Dust | Water | What it means in practice |
|---|---|---|---|
| IP54 | Protected | Splashing | Indoor, or outdoor under cover. Not for direct rain |
| IP65 | Dust-tight | Low-pressure jets | Outdoor general purpose, rain from any angle |
| IP66 | Dust-tight | Powerful jets | Washdown, coastal, heavy weather, hose cleaning |
An IP number is a test result on a sample, not a promise about your cabinet. Whether your design holds it depends on the seal compression, the number and position of latches, the gasket material, and whether the cable entries were designed in. We tell you what the drawing you sent us can hold, and what would have to change for the next rating up.
Material choice for outdoor service
| Environment | Recommended | Why |
|---|---|---|
| Inland, non-corrosive, cost-driven | SPCC mild steel, powder coated | Cheapest route to IP65; coating must mask threads and earth points |
| Coastal, marine air, de-icing salt | Stainless 316 | Molybdenum content resists chloride pitting that eats 304 |
| Coastal with a sealed finish and budget limit | Stainless 304, edges sealed | Workable if cut edges and welds are protected; not equal to 316 |
| Weight-sensitive, or heat-sensitive equipment | Aluminium 5052 / 6061 | Light, and conducts heat away from internals |
Thickness we run: 0.5–18 mm mild steel, 0.5–15 mm stainless, 0.5–10 mm aluminium. For a weatherproof cabinet, gauge matters less than stiffness — a 1.5 mm door with a stiffener beats a 2 mm door that bows and opens the seal.
What we run in-house, and what goes out
| Operation | Where |
|---|---|
| Laser cutting, CNC bending, welding, assembly | In-house (3 lasers, 4 × 250 t press brakes, 10 welding stations) |
| Brushing and mirror polishing | In-house |
| Powder coating, passivation, anodising, plating | Audited partner lines — we specify and inspect |
We do not own the coating or plating lines. We say so here rather than let you find out at the factory audit.
What to put on the drawing
- IP rating and the test condition — “IP66” alone is not enough; say whether it is tested as-built or with the door closed by hand
- Gasket material and whether it is user-replaceable — this decides whether the cabinet is repairable in the field
- Roof form — sloped, domed or flat, with the overhang dimension
- Cable entry positions and sizes, and whether the gland plate is welded in or bolted on
- Latch count and position — one latch in the middle of a tall door will not hold IP66
- Earth point location — and whether it is masked before coating
- Coating masking — threads, mating faces, earth points, gasket channel
- Thermal path — vent position, or whether the cabinet is sealed and heat is conducted out through the wall
Related reading
- Electrical enclosures and cabinets: the full selection guide
- IP66 enclosures: what the rating really means
- Stainless steel enclosures: 304, 316 and 430
- Enclosure thermal management
Frequently asked questions
Can you guarantee an IP rating?
We can build to the design that achieves it, and we will tell you what your design holds. We do not issue IP certificates ourselves — ingress testing on the finished equipment is arranged by you or the certification body. What we provide is the dimensional and process record showing the cabinet was built to the specified seal design.
Stainless 304 or 316 for a coastal site?
316, if the budget allows. 304 will pit at the welds and cut edges in chloride-laden air, usually within a few years. If the project is locked to 304, we can seal the edges and specify a coating that slows it, but that is damage limitation, not equivalence.
Do you supply the gasket, or do we?
Either. If you specify the gasket, tell us the profile and the material — it changes the channel geometry. If you leave it to us, we will propose a captured-channel design with a replaceable seal and quote it as part of the cabinet.
What about internal condensation?
A sealed cabinet that breathes with the day/night cycle will condense internally even with no external leak. The usual fix is a drain-and-breather element, or a small controlled-pressure vent. Both are drawn into the wall rather than drilled afterwards.
Can you build a single prototype outdoor enclosure?
Yes. Simple laser-cut and bent samples are 3–7 days; complex first articles with welding, hardware sourcing or a coating trial are 15–20 days. Production batches run 25–35 days, quoted after drawing review. Freight is quoted separately to your port.
Do you hold ISO 9001 certification?
Our quality system is documented to ISO 9001. We do not hold a third-party ISO 9001 certificate and do not claim one. Third-party audit evidence is available under NDA: TÜV Rheinland MIC-ASI243729 and Bureau Veritas MIC-ASR263630.
Send the drawing and the site
Send the drawing with the destination, the environment (rain, salt, washdown, UV) and the cable-entry layout. Those three decide whether the cabinet needs IP54 or IP66, and whether it should be mild steel or 316. We will tell you honestly what your design holds, and what would have to change to reach the next rating up.