What an IP68 rating means for an electronics enclosure

An IP68 enclosure is rated by its manufacturer for continuous submersion in water, under conditions of depth and duration the manufacturer declares, per IEC 60529. The rating does not come from a fixed test depth: the standard defines how the test is run, and you and the maker agree on how deep and how long. That is why two IP68 boxes can behave very differently underwater.

If you are enclosing electronics and the first instinct is to fill the box with potting compound, slow down. Potting is one legitimate path, but it is usually the harder and costlier one. A genuinely sealed enclosure, correctly glanded and thermally designed, solves the same problem and stays serviceable. This article walks through what IP68 really tests, when potting makes sense, and what changes in the design when a box will live underwater.

What the two digits actually say

The IP code comes from IEC 60529. The first digit covers solids and dust; the second covers water. IP6X means no dust ingress at all. The second digit is the one that matters here: an 8 means the equipment is suitable for continuous submersion under conditions the manufacturer specifies.

Compare that with a 7. IP67 is tested by immersing 1 meter deep for 30 minutes, a fixed figure written into the standard. IP68 has no fixed figure. The standard says the depth and duration are a matter of agreement, and the manufacturer states them. In practice, many makers default to something like 1.5 to 2 meters, but you cannot assume it. A rating of IP68 with no stated depth is an incomplete spec.

If your real environment is rain, hose spray or washdown rather than submersion, you likely do not need the 8. The water jet tests behind IP66 are a different and, for most industrial sites, more relevant question, and we compare them in the IP65 vs IP66 water jet test differences article. Our IP rating chart guide covers every digit in the code.

What is tested, and what is not

The submersion test places the enclosure under water at the agreed depth for the agreed time and then checks for ingress. Three things about the test matter for your design:

• It is a fresh-water test. Chemicals, solvents and chlorinated or saline water are not covered by the code. Salt water is its own materials problem.
• It is a static test. Pressure waves, currents, tidal cycling and temperature swings during submersion are not part of the procedure. A box that passes the tank can still weep in a real sump.
• It says nothing about what happens inside. Water vapor passes through gaskets by diffusion over time. An IP68 enclosure can still collect condensation internally, which is the same physics we cover in the condensation in a sealed enclosure article.

Ratings are manufacturer ratings; the standard's second digit is earned by the maker's own declared conditions, not by an independent certification body unless the spec calls for one. Treat the number as the start of a conversation about conditions, not the end of it.

Potting versus a sealed enclosure

Potting means embedding the board in a compound, usually an epoxy, urethane or silicone resin, so there is nothing left to seal. It is a valid approach, and for some products it is the right one.

Where potting wins: tiny assemblies, disposable devices, extreme vibration, and boards with no user-serviceable parts. If the assembly costs little and gets replaced whole, potting removes the enclosure problem entirely.

Where a sealed enclosure wins: anything you may rework, upgrade or repair; anything with significant heat; anything with external connectors, displays or controls. Potting has three practical costs:

1. Rework is effectively impossible. A failed component means scrapping the assembly. Over the life of a control system that usually costs more than the enclosure ever did.
2. Heat has nowhere to go. Most potting compounds conduct heat roughly 100 times worse than aluminum, and hundreds of times worse than stainless steel. A potted board runs hotter than the same board in air, and thermal cycling between hot and cold states tears fine wire bonds and solder joints apart over time. Failures in heavily potted power supplies are a classic example.
3. Every penetration is a leak path. Wires leaving the potting must be strain-relieved and bonded well, or wicking along the conductor pulls water straight into the assembly. Some jacket materials also bond poorly to common resins.

There is a middle path: pot or conformal-coat the board for moisture protection, and still put it in a sealed enclosure. The coating protects against the condensation that will eventually form inside any sealed box; the enclosure handles the water outside.

Heat: the problem a submerged box cannot vent away

Every watt that goes into the enclosure comes out as heat. In a normal panel you can move air with a fan or filter; in an IP68 box, no ventilation is possible, because any opening that vents air lets water in under submersion pressure. Internal circulating fans only move heat around; they do not remove it.

The only path out is conduction through the enclosure walls. For a small sealed stainless box, the wall area and the temperature difference set the limit. As a rule of thumb, a 10 x 8 x 6 in (250 x 200 x 150 mm) sealed stainless box dissipates roughly 20 to 30 W before internal temperatures run more than about 20 C above ambient in still water or still air; submerged in moving water the margin is better, because water strips heat from the walls far faster than air does. Run the actual numbers with the method in our enclosure heat calculation guide before you commit to a board design.

If the load exceeds what a sealed box can shed, the options change character entirely: active cooling equipment rated for submersion is rare and expensive, so the practical answers are a lower-power board design, or moving the electronics somewhere drier and running only sensors and actuators underwater.

Condensation and the inside of a submerged box

Here is the detail that surprises most designers: a perfectly sealed IP68 enclosure still gets wet inside. Water vapor diffuses through gaskets over months, and every thermal cycle pumps humid air in and out slightly as the internal pressure changes. When the box then cools at depth, that vapor condenses on the walls and the board.

The standard remedies still apply underwater, with adjustments:

• Desiccant packs inside the box absorb the vapor; size them for the box volume and plan to replace them at service intervals.
• A conformal coating or a light potting of just the sensitive board areas protects the electronics from the droplets that form anyway. This is where a limited, targeted potting makes sense, rather than filling the box.
• Avoid organic gasket materials that stay saturated. Closed-cell silicone and EPDM hold up better than open-cell foams in continuous wet duty.

Our enclosure condensation guide covers dew point, heaters and drains for the general case, and the humidity sensing in a sealed enclosure article shows how to measure what is actually happening inside. Note that a heater and a drain, the standard fixes in an atmospheric box, are usually not options underwater, which pushes the design toward desiccant plus coatings.

Cable entry: where most submersible designs fail

The enclosure body rarely leaks; the penetrations do. Under 2 meters of head you have roughly 20 kPa (about 3 psi) pushing water through any imperfect seal, continuously, for the life of the installation.

For a genuine IP68 build:

• Use glands rated for the same depth as the box, with the correct hole tolerance and a sealing washer on a flat, unpainted surface. A gland rated IP68 at a stated depth keeps its rating only if installed exactly as documented.
• Prefer glands with an inner seal that clamps the cable jacket, not just an O-ring on the threads.
• Keep the number of penetrations as low as the design allows, and group them so a single leak check covers them.
• Where a connector is needed instead of a bare cable, specify a connector system rated for the same submersion depth, not a generic round connector with a rubber boot.

Gland selection and hole specification are the same discipline as any sealed enclosure; the cutouts, glands and HMI windows guide covers hole sizes and gland fit, and the outdoor junction box sealing article shows the drip-loop and drain habits that matter as soon as the cable leaves the gland. Underwater, the drip loop still matters: it keeps water that runs along the cable from sitting at the gland.

Materials for continuous wet duty

Submersion raises the stakes on the enclosure material. Fresh, clean water is easy on 304 stainless. Salt water, brackish water, or water with chlorides and sanitizers pushes you to 316L, and even then crevice corrosion under gaskets and fasteners is the failure mode to watch. Our aluminum vs stainless steel selection article covers the material trade-offs, and for corrosive service generally, the junction box inspection checklist for corrosive areas is a sensible maintenance starting point.

We build 304 and 316L stainless wall-mount and HMI enclosures, made to your dimensions and cutouts and delivered in 10 business days. They are rated NEMA 4X / IP66 by the manufacturer; not UL listed. That rating covers washdown, hose-directed water and driving rain; it does not cover continuous submersion, and we say so plainly. If your application is a sump pit, a well or a tank interior, get the declared depth and duration from the supplier in writing, and confirm the gland and connector ratings match it.

What to specify

A short-form spec for an electronics enclosure that will be submerged:

1. Depth and duration, stated in meters and hours, agreed with the supplier. Never just "IP68".
2. Wall material matched to the water chemistry: 304 for clean fresh water, 316L for chlorides and salt.
3. Heat load in watts from the board designer, and a conduction calculation that shows internal temperature stays within component limits.
4. Gland and connector ratings equal to the enclosure rating, with hole sizes specified on the drawing.
5. Internal moisture plan: desiccant volume, conformal coating, and any targeted potting of sensitive circuits.
6. Service plan: how the box is opened, inspected and resealed, and how often.

If you decide potting alone is the answer after reading this, fine, but make that decision on cost-per-assembly and heat, not because the sealing problem looked hard. A purpose-built sealed box is usually the cheaper route, and it leaves you a board you can still fix.

One related read if your electronics include a panel PC or display at the heart of the build: the guide to panel PC heat inside an enclosure covers the thermal and moisture trade-offs of potting industrial electronics in more depth.

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