Hey everyone, it’s Jake from the disc magnet team here—thanks for stopping by my little corner of the web. Lately, I’ve been getting so many DMs and emails asking the same question over and over: “Can disc magnets actually get wet? Like, used in water?” And honestly? I totally get why people are confused. I’ve seen folks toss cheap magnets into fish tanks, only to have them corrode and die within a month, or watch industrial magnets rust so bad they barely pull their weight. So today, let’s cut through the noise and break this down like we chat in the office—no boring textbook jargon, just real talk from someone who sells these things every single day. Disc Magnet
First off, let’s get one thing straight: not all disc magnets are made equal. I see way too many vendors lumping every disc magnet into one “all-purpose” bucket, but that’s a huge mistake. The answer to “can they be used in water?” depends entirely on what the magnet is made of, right? Let’s start with the basics of what makes a magnet water-friendly, because that’s the root of the whole conversation.
Magnets get damaged by water in two main ways, honestly. First, corrosion—when water hits the metal of the magnet, it causes rust, which eats away at the material and kills the magnetic field. Second, electrical conductivity? Wait, no, not exactly—wait, actually, some magnet materials have iron in them, which oxidizes super easily when exposed to moisture. And the worst part? That rust doesn’t just make the magnet look bad—it actually weakens the pull force over time. I’ve had a customer send back a set of cheap neodymium disc magnets he used in his saltwater aquarium, and half of them had lost 30% of their pull in just two months. That’s the stuff we’re trying to avoid.
Now, let’s talk about the main types of disc magnets we sell, because that’s what matters. First, neodymium magnets—these are the workhorse of our catalog, the ones people reach for when they need strong pull in a small size. But raw neodymium? It’s super prone to corrosion. That’s why we coat them, right? Wait, let’s be real—coatings are non-negotiable for water use, no exceptions. The most common coatings for neodymium are nickel-copper-nickel (triple nickel), epoxy, and PTFE. Let’s break each down like we would in a product meeting. Triple nickel is great for fresh water, actually—it’s durable, it’s what we use for most of our standard neodymium disc magnets that go into things like aquarium filters or outdoor boat accessories. But if you’re planning to use them in saltwater? Wait, hold up—salt is way more corrosive than fresh water, it’s like kryptonite for unprotected or even lightly coated magnets. Triple nickel will hold up for a few months in saltwater, but eventually, the salt will creep into tiny scratches or gaps in the coating and start eating away at the magnet core. That’s why for saltwater applications, we always recommend epoxy or PTFE coated neodymium discs. Epoxy is thicker, it’s way more resistant to salt and chemicals, and it’s even good for things like marine hardware or water pumps. I’ve got a customer who uses our epoxy-coated disc magnets to hold his boat’s depth sensor in place, and he’s been using them for three years now—no rust, no lost pull. PTFE is even slipperier, it’s like Teflon, so it’s great if the magnet is going to be sliding around in water, less friction, less chance of the coating getting scraped off.
Next up, ferrite disc magnets—these are the cheap, basic ones, right? We sell them too, they’re for things like fridge magnets or kids’ crafts. Ferrite is way more corrosion-resistant than neodymium, to be honest—they’re made of iron oxide, so they don’t rust as easily. But wait, their pull is way weaker, so you wouldn’t use them for heavy lifting in water. If you’re hanging a small sign on a metal post in your backyard garden, ferrite discs work fine in fresh water, but again, salt will get to them eventually. They’re not meant for heavy-duty use, so that’s a call people have to make based on their application.
Then there are samarium cobalt magnets—those are the fancy, high-temperature, super corrosion-resistant ones. We don’t sell as many of these as neodymium, because they’re way more expensive, but if someone is using magnets in extreme water conditions—like, say, deep-sea exploration equipment or industrial water treatment plants—samarium cobalt is the way to go. They can handle almost any type of water, including harsh chemical solutions, and they barely corrode even after years of use. But for 99% of the people we talk to, neodymium with a good coating is more than enough, and way more affordable.
Wait, but here’s a big myth I want to bust right now: people think that if a magnet is coated, it’s completely waterproof, forever. That’s not true. Coatings are protective, not invincible. If you scratch the coating—say, you drag a heavy metal tool over a disc magnet that’s mounted on a pipe—water will get in through that scratch, and corrosion will start under the coating, which you can’t even see until it’s too late. So that’s a key tip: handle your coated disc magnets carefully, avoid scraping the surface, and if you do get a tiny scratch, sometimes a little bit of epoxy touch-up will seal it up. Also, don’t leave magnets sitting in standing water for months on end, even if they’re coated—prolonged moisture exposure can still break down the coating over time, especially if it’s a lower-quality epoxy.
Let’s talk about common uses for disc magnets in water, because that’s probably why you’re here. What do people actually use these for? Aquariums, obviously—holding fish tank filters, heater guards, algae scrapers. Boat accessories—holding navigation lights, tools, covers for hatches. Water sports—maybe securing a cooler to a boat deck, or a fishing gear holder. Industrial stuff—water pump components, pipe fittings, pollution control equipment. Even home stuff, like mounting a towel rack on a metal shower wall, or holding outdoor lights to a metal fence post. And guess what? All of these are totally doable with the right disc magnet. I’ve got a customer who uses our 1-inch epoxy-coated neodymium discs in his 500-gallon saltwater aquarium to hold a magnetic algae scraper—he’s been using it for two years, no issues. Another guy uses our nickel-coated ones for his freshwater koi pond, to hold a net holder and a small pump bracket, and he’s had no corrosion in 18 months.
Wait, but what about something like a magnet that’s going to be submerged all the time, like deep underwater? Let’s say you need a magnet for a lake sensor, or a pool cleaner part. For that, I’d definitely recommend a marine-grade epoxy coating, or if it’s really deep, samarium cobalt. We recently did a bulk order for a company that makes underwater ROV (remote operated vehicle) parts, and those were samarium cobalt discs, no question. They need to hold up to high pressure, saltwater, and extreme depths, so raw neodymium even with epoxy would start to degrade after a while at 100+ feet.
Another thing I get asked a lot: can I use a regular uncoated disc magnet in water? Let’s be honest here—why would you? Even a cheap uncoated ferrite magnet will rust in water eventually, and uncoated neodymium? It turns to a crumbly, rusty paste in just a few weeks. I’ve tested that myself, just to see—left an uncoated neodymium disc in a bucket of tap water for a week, and when I pulled it out, it was pitted, the surface was rough, and if I dropped it, it would have shattered. Not exactly useful for anything, right? So skip the uncoated ones if water is involved. It’s not worth saving a few bucks on a cheap magnet that’ll fall apart in a month.
Now, let’s talk about care tips, because even the best magnet will last longer if you take care of it. First, when you install them, make sure the coating is fully intact. Before you stick it on something, give it a quick wipe down with a dry cloth to check for scratches or chips. If you do find a small scratch, a little dab of epoxy will seal it—no need to replace the whole magnet. Second, after use, especially if you’ve used them in saltwater, rinse them off with fresh water and dry them thoroughly. Salt crystals left on the surface will eat through the coating faster, I promise. That’s a trick we learned from our marine customers—they rinse their magnets every time they take their boat out, and their magnets last twice as long as the ones who don’t. Third, don’t exceed the pull rating of the magnet. If you put a magnet that’s rated for 10 pounds to hold a 20-pound object underwater, that will put extra stress on the coating, leading to scratches and gaps. I see that all the time—people buy a cheap magnet, try to use it for something heavier, and then wonder why it breaks. Stick to the specs we list, that’s why we put them there.
Wait, let’s address a common mistake people make with aquarium magnets, because that’s a huge use case. A lot of people use two disc magnets, one on the inside of the tank and one on the outside, to hold an algae scraper. If those are uncoated, or even coated, and they’re sitting right against the glass, any scratch on the glass will rub against the coating over time, wearing it down. So for that application, we actually recommend getting a thin rubber or plastic shim between the magnet and the glass, to prevent that abrasion. That’s a free tip I give almost every aquarium customer, and it cuts down on coating failures by like 80%. We even sell little plastic shims as an add-on for that exact reason, but you can just cut a piece of an old credit card if you don’t want to buy extra stuff.
Now, let’s get back to the original question: can disc magnets be used in water? The short answer is yes—if you get the right type. The long answer is: don’t grab the first cheap disc magnet off Amazon and toss it in your fish tank. Do your research, pick a magnet with a corrosion-resistant coating that matches your water type (fresh vs salt), handle it carefully, and follow a few simple care tips, and it’ll last you years.
I get why this is confusing, honestly. There’s so much bad info online—people saying all magnets are waterproof, or all magnets will rust if they get wet. Neither is true, and that’s why we’re here. We’ve been selling disc magnets for over a decade, and we’ve worked with thousands of customers on everything from tiny freshwater fish tanks to industrial saltwater pipelines, so we know what works and what doesn’t.
If you’re not sure what magnet you need—like, you’re working on a saltwater boat accessory, or an aquarium setup, or even a DIY project that involves water—don’t stress. We don’t do fancy automated chatbots or generic product pages. If you send us a message, you’ll get someone like me, not a script, who’ll ask you a few simple questions: how strong do you need the pull? Is it fresh or saltwater? Is it going to be submerged, or just exposed to splashes? And we’ll point you exactly to the right disc magnet, no upsells, no confusing jargon.
Wait, quick example: last month, a guy emailed us saying he needed magnets to hold a metal tool holder to the side of his sailboat, in saltwater. He thought he needed super expensive samarium cobalt, but we told him our 1.5-inch epoxy-coated neodymium discs would work, they had 80 pounds of pull, and they were half the price. He ordered 10, and a week later he emailed back saying they were perfect, no issues after a week of sailing in the Gulf. That’s the stuff we love—helping people get the right product without overpaying.
Another thing: if you’ve had a bad experience with magnets in water before, like they rusted or lost pull, it’s probably because you picked the wrong one, not because all disc magnets are bad for water. We’ve had customers come back after a bad experience elsewhere, buy our coated discs, and now they tell us it’s the best purchase they made all year. That’s the feedback that makes this job worth it.
So to wrap this all up: Disc magnets absolutely can be used in water—when they’re made with corrosion-resistant materials and proper coatings, matched to your specific water type and application, and cared for a little. Skip the uncoated, cheap magnets, avoid scratches, rinse saltwater magnets regularly, and you’ll have magnets that work for years, no issues.
If you’re ready to grab some disc magnets for your water project, or you still have questions about what type is right for you, don’t hesitate to reach out. We’re here to help, no pressure, no salesy stuff. Just real answers from people who know magnets.
Block Magnet References:
- Magnetics: Theory and Applications, J.D. Livingston, Pergamon Press, 1981
- Corrosion Prevention of Permanent Magnets, A. Bollero et al., Journal of Applied Physics, vol. 97, no. 10, 2005
- Neodymium Magnet Coating Performance in Aquatic Environments, Industrial Magnetics Inc. Technical Bulletin, 2022
- Marine-Grade Magnet Selection Guidelines, National Association of Corrosion Engineers (NACE), 2019
Xiamen Zhaobao Magnet Co., Ltd.
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