Modern RC hobbies (cars, boats, drones, planes) often tempt us to race through puddles or splash around. It’s tempting to call electronics “waterproof,” but caution is needed. The ESC (electronic speed controller) that drives your motor and the radio receiver that gets your signals have very different needs. ESCs handle high currents and get hot; receivers only use a tiny amount of power. Receivers can sit safely in a sealed box, but ESCs usually require airflow. Always remember: water and electronics don’t mix well hosim.com. Even so-called waterproof setups are usually only splash-resistant. Here we explain the differences, risks, and how to protect these parts with coatings, enclosures, or potting.
How ESCs Differ from Radio Receivers
- Power & Heat: An ESC drives the motor by switching high currents. This creates heat. ESCs often have big aluminum heatsinks or even cooling fans to shed heat eurorc.com. For example, the RC4WD Outcry III ESC warning says “Product emits heat, heatsink may become extremely hot” store.rc4wd.com. By contrast, a radio receiver just uses a little power to process signals (it usually runs off the ESC’s small 5V BEC). A receiver barely warms up at all.
- Ventilation Needs: Because ESCs run hot, they need airflow or heatsinks. Putting an ESC in a sealed box will trap heat and can make it overheat. Even with coatings, be sure to leave enough heat-sinking. Receivers generate no real heat, so they’re often placed inside a waterproof plastic box or “receiver box.” Manufacturers put rubber grommets or O-rings on receiver boxes to seal them. For example, many waterproof RC kits include a plastics box: these can keep rain out, but the seal isn’t perfect. As Axial notes, water “can seep inside” a receiver box if submerged, and you can’t even see it inside axialadventure.com. So receivers are fine sealed up, but ESCs need breathing room.
- Signal vs. Motor Load: Water between antenna and transmitter can block radio signals. Even if your receiver survives, water is a dielectric that weakens 2.4GHz signals. Axial warns that submerging a receiver may cause signal loss or interference. An ESC doesn’t care about radio waves, but if the receiver loses signal underwater, the car may become unresponsive.
In short: ESCs run hot and need heat sinking (so full sealing is tricky), while receivers draw little power and heat and can live in a waterproof box (as long as no water actually gets inside).
Why Full Submersion is Risky
Even water-resistant electronics are not meant for full submersion. Here are the big dangers in high-power RC setups:
- Overheating: Water blocks airflow. An ESC generates a lot of heat when driving a motor, especially at high current. If you put an ESC underwater, its heat can’t escape into air. Hobbywing explicitly warns that even their waterproof ESC should not be submerged for long, because it will still heat up hobbywing.com. In practice, a submerged ESC can quickly overheat and shut down or fry.
- High Current & Short Circuits: The ESC and motor draw tens of amps. If water gets into connectors or onto a circuit board, those high currents can find unintended paths. Salt or mineral ions in water make it a conductor. This causes short circuits or melted traces. High currents plus water is a recipe for a blown ESC or BEC, and even melted wires.
- Corrosion: Water, especially salt water, is highly corrosive to electronics. Metal traces, solder joints, and connectors corrode quickly once wet. Companies that make true underwater ESCs use special cabling: for example, HobbyWater’s ROV ESCs use cables with “seawater corrosion resistant polyurethane” and tinned copper cores hobbywater.com. Ordinary RC parts are not built for that. Even a little moisture over time will leave rust inside your ESC or BEC, causing failures.
- Radio Signal Loss: As noted above, any water layer between the receiver antenna and your radio will weaken the signal. So even if the electronics still work, your car might suddenly lose contact underwater.
- Boating vs. Mud Racing: Riding through mud or rain is usually fine (just keep speed down to avoid splashes reaching electronics). But plunging an RC into water is much worse. IP-ratings like IP67 or IP68 often mean splash/dust resistance, not true submersion. For instance, Hobbywing’s QuicRun WP-16BL30 G2 is IP67 rated (meaning splashproof), but their specs warn: “Do not submerge the product in water for extended periods”. Over time, seals wear and any gap can let in water.
Bottom line: Submerge at your own risk. While you can drive an RC through puddles (keeping electronics sealed), completely underwater operation usually requires special ESCs and strong sealing. Even a “waterproof” ESC is typically only splashproof.
Conformal Coating vs Enclosures vs Epoxy
When waterproofing electronics, there are three main approaches. Each has pros and cons:
| Method | Pros | Cons | Heat Handling |
|---|---|---|---|
| Conformal Coating (silicone or acrylic paint) | Thin, lightweight. Protects traces and components from moisture, dust and corrosion testequity.com. Allows heat to escape. Easy to apply by brush or spray. (Some coats even fluoresce under UV to check coverage oscarliang.com Amazon.) Can be peeled off or soldered through if rework is needed. | Not 100% waterproof (just water-resistant). Requires careful application (avoid connectors and controls). Flammable/toxic (work in ventilated area). | Minimal heat trap due to thin layer. Heat sinks can still work normally. |
| Enclosure/Box (gasket-sealed case) | Blocks splashes from reaching electronics. Can open/close easily for maintenance. Keeps sensors (e.g. accelerometers) in normal air. | Needs good seals and grommets on all wires. Still only splash-proof; pressure or leaks may let water in. Traps any moisture that does get inside. | Good ventilation depends on design (often used only on low-heat parts like receivers). ESC in a box without vent will overheat. |
| Full Epoxy Potting (filling or dipping) | Creates a heavy-duty, permanent seal around the entire board. Excellent water immunity if done right. | Completely seals and hardens; board can’t be opened or repaired. Very difficult to rework. Can add weight. Insulates electronics, so heat has trouble escaping (each part gets its own blob). | High heat trap. Epoxy or silicone potting will conduct some heat, but generally prevents normal cooling. Potting requires special thermally-conductive compounds for ESCs endless-sphere.com, or a huge risk of overheating. |
In practice, most hobbyists use conformal coating for ESCs and receivers. Popular products include silicone-based sprays and gels. For example, MG Chemicals 422C is a silicone conformal that cures flexible and strong: it “provides strong protection against moisture, corrosion, fungus, dirt, dust, thermal shock, short circuits”. It dries in minutes and even glows under UV so you can confirm full coverage. CowRC (Holmes Hobbies) sells Cow-Formal silicone coating, advertised as a thick single-coat solution “used in-house by Holmes Hobbies” cowrc.com.
Enclosures are most often used for receivers: there are plastic receiver boxes or fiberglass housings that seal with O-rings and silicone. These keep rain out and let the receiver sit safely under the chassis. Keep in mind that no simple box can survive deep submersion forever. Gaskets and silicone must be checked often. On the positive side, sealed boxes ensure that any water inside is limited; you can often open and dry them quickly after a run.
Full potting (with 2-part epoxy or resin) is rare for hobby ESCs, because of the heat problem. It’s very common in marine electronics (such as ROV controllers or e-foil ESCs). Those use special thermally conductive epoxies and often add cooling fins on the outside. For an RC model, potting an ESC means it’s glued shut permanently. Pro’s: ultimate water resistance. Con’s: trapped heat and no fixes. One online expert notes that potting compounds often use metal-filled epoxy (“thermally conductive potting epoxy”) to get heat out, and compares it to easier-to-use coatings: “Conformal coating is easier to work with and gives most of the benefits of potting”. In contrast, simple rubberized sprays (like Plasti Dip) are poor for high-power electronics because they insulate heat too much.
Step-by-Step: Conformal Coating an ESC
If you choose to conformal-coat your ESC, follow these steps carefully (and always prioritize safety):
- Safety first: Remove power. Disconnect the battery. Work in a well-ventilated area or outdoors. Conformal coatings can contain solvents and are flammable. Wear gloves and eye protection if possible.
- Prep the ESC: Take the ESC out of the car or boat. If it has a case or cover, open it to expose the circuit board. Make sure any switches or buttons have a rubber cap or mask them, so coating doesn’t glue them shut.
- Clean the board: Wipe the PCB with 90%+ isopropyl alcohol to remove grease or residues. Let it dry fully.
- Protect sensitive parts: Plug in all the connector cables (motor, battery, receiver) so that the contacts are mated inside their plugs. This ensures the coating won’t flow into the connector holes. You may also mask any screw threads or components you want to avoid covering.
- Apply coating: Using a brush-on silicone conformal (like MG 422C) or a spray designed for electronics, coat the board evenly. Hold the ESC so the board is vertical and apply a thin coat of coating, like painting a model. Make sure all exposed traces and solder joints are covered. Focus especially on metal parts (solder, MOSFET tabs, small wires). Avoid saturating connectors, potentiometers, or ventilation holes. A brush is good for control. If using spray, do several light passes rather than one heavy one. Each layer will look somewhat cloudy at first, then clear as it dries.
- Check coverage: If using a UV-indicator type, use a UV light to spot any gaps. Otherwise, inspect carefully. If you see bare metal spots, re-coat. It’s often best to do two coats. Let the first coat dry a few minutes (or as per product instructions) before the second. Most silicone coats become tack-free quickly (e.g. 10–20 minutes) and fully cure in hours. Waiting overnight ensures full curing.
- Cure time: After coating, let the ESC sit undisturbed for the recommended cure time (often 12–24 hours for silicone). This ensures all solvents have evaporated.
- Reassemble: Remove any masking tape. Reinstall the ESC cover or case. Ensure no wires are pinched. Reattach to your model. Turn on and test! Your ESC should now withstand rain and splashes much better.
Remember: coating an ESC doesn’t make it permanently waterproof – it mainly prevents corrosion and shorts. Inspect periodically (especially after heavy use) to ensure the coating didn’t crack.
Alternatives: Buy Waterproof ESCs vs. DIY
Finally, consider the alternatives to modding your ESC:
- Buy a waterproof-rated ESC: Some hobby ESCs are built for wet use. For example, Traxxas offers marine brushless ESCs (Velineon VXL series) in waterproof cases, and some Castle Creations or Hobbywing models are splashproof. Hobbywing’s new QuicRun WP 16BL30 G2 is IP67-rated, meaning it resists dust and splashes. (However, even they warn not to fully submerge it long-term.) RC4WD’s Outcry III is sold as “waterproof” and can handle shallow water for limited time. These are great if you want plug-and-play convenience, but they tend to be more expensive. Also, true submersible ESCs (for ROVs) are much pricier. If your application is casual mud/rain driving, a marine ESC is safe choice.
- Receiver/ESC enclosure mod: Some users build a custom sealed box. You can epoxy a plastic box around the ESC (or ESC/receiver combo), with silicone-sealed wire glands. This way the electronics are not directly coated. It’s messy but keeps the board dry. The downside is trapped air that can condense moisture. Sealed boxes for ESCs often need a tiny breather or must be dried after a run.
- Liquid Electrical Tape: Products like Gardner Bender Liquid Electrical Tape can be brushed on boards and connectors. They form a rubbery waterproof seal. It’s easy and removable, but it adds some insulation (which traps heat more than silicone) and isn’t as tough as silicone coatings.
- Corrosion sprays: Some hobbyists simply treat their electronics annually with a moisture repellent like CorrosionX spray (often used in boating) as a preventative. Castle Creations’ engineer even recommended periodically dipping an ESC in CorrosionX, noting it displaces water and needs annual reapplication. This isn’t full waterproofing, but it repels moisture in connectors and on traces.
In the end, no method is perfect. Buying a product rated for water is simplest. If you go DIY, conformal silicone coating is a popular middle ground: it’s fairly easy (no need to drill holes or seal a box), allows heat to escape, and gives strong corrosion protection. Combining methods is common: e.g. coat the ESC, then also place it in a splashproof enclosure or use connector boots.
By understanding the differences and pitfalls, you can choose the right approach to protect your ESC and receiver. Whether you mod your own board with coatings, or buy an IP-rated ESC, always keep an eye on temperatures and seals during use. With the right prep, your RC fun needn’t stop when it starts raining – just know the limits!
Sources: Insights drawn from hobbyist guides and manufacturer notes, including Axial’s waterproofing tips, Castle Creations advice, Hobbywing specs, MG Chemicals datasheets, and practical tutorial steps.