The Best Epoxy for Cast Iron

Cast iron is a bit of an umbrella term, considering there are so many types of the alloy in use both industrially and in domestic applications. From ductile cast iron to gray cast iron, the alloy can be found anywhere from drainage and water pipes, columns and posts, down to cast iron skillets and pans popular for how evenly they can withstand and distribute heat. Nonetheless, despite their heavy-duty properties, even cast iron implements can sustain damage – a cracked or leaking pipe, a broken bench leg or a rusted ornate knocker are all quite worrisome if you consider the possibility that you might have to redo a chunk of your plumbing, buy an entirely new garden bench or bid goodbye to a decorative doorknocker you’ve had around for years.

There is ­a solution though – the right epoxy treatment. Picking a powerful epoxy boasting the desired specs for adhesive ability, strength, longevity, and wear- and tear-resistance can let you patch up cast iron homeware and hardware in a jiffy, without having to opt for more expensive repair work or having to discard the whole thing altogether, investing in something brand new and likely expensive. We’ve considered the options – here are our picks for the best epoxy for cast iron.

J-B Weld 8281 Professional Size Steel Reinforced Epoxy

With exceptional performance when it comes to metal-to-metal adhesion, this two-component epoxy is a heavy-duty option for anything from marine and automotive applications to household repairs, handyman projects and some quick-fix plumbing repairs. The epoxy takes just 4-6 hours to set, curing within 15-24 hours and darkening to a dark gray, after which it can be sanded, drilled, filed, tapped, painted and more to suit your needs. With a tensile strength of 3,960 PSI and temperature resistance up to 550°F, this 1:1 mixing ratio epoxy has incredible bonding power, capable of holding together metal components or sealing in gouges and seams, fixing up radiator cracks, leaky oil pans and broken welding and increasing the lifespans and functionality of not just cast iron implements but other metal structures, all in just a few hours where the epoxy does most of the work. Waterproof, chemically and thermally resistant, and with incredible adhesive properties, this epoxy can also be used for fiberglass, concrete, brick and more.

J-B Weld 8276 KwikWeld Quick Setting Steel Reinforced Epoxy

Delightfully inexpensive, the value-for-money payoff of this epoxy is insane – for a great pocket-friendly price you get a two-component epoxy adhesive you can use not just for quick-fixes like reattaching a loose handle on a cast iron pan or filling in a hole inside, but also for heavy-duty applications like repairing or reinforcing plumbing, automotive and household repairs, and more. The 1:1 mixing ratio epoxy sets in about 4-6 hours, curing completely in 15-24 hours to a dark gray. Post-curing, the adhesive can be sanded, filed, tapped, drilled or otherwise shaped as you need it, and even painted over if you’d like the finished product to look more aesthetically appealing. With a tensile strength of 2,424 PSI and a temperature resistance of up to 300°F, it may be sporting lower specs than our top pick but nonetheless goes above and beyond what you’ll need for anything from patching up leaks and holes in old cast iron pipes to plugging up voids in hydraulic pistons. Usable on many different surfaces, from metals to fiberglass and concrete, the epoxy cures to a rigid, non-shrinking solid that is thermally and chemically resistant, waterproof and highly durable.

Permatex 84109 PermaPoxy 4 Minute Multi-Metal Epoxy

As the name itself stipulates, this epoxy adhesive is specifically engineered for use on metal surfaces, for metal-to-metal adhesion, heavy-duty mechanical applications and multi-component assembly. A powerful two-component epoxy with a tensile strength and strain resistance of an incredible 4,500 PSI, the adhesive sets in just 4 minutes, so you won’t have to worry about clamping up the components you’re gluing together or arranging for additional support while the epoxy cures. The adhesive cures completely in 24 hours, settling into a dark gray color, and can then be shaped, filed, sanded, and painted over depending on your needs. Suitable not just for cast iron but a whole range of metals including aluminum, copper, brass, stainless steel and more, this powerful adhesive can be used for anything from plugging leaks and gaps in metal and woodwork to mounting up metal components, reinstalling fastenings and reinforcing bolts and welded seams.

Blue Magic 16002TRI QuikSteel Steel Reinforced Epoxy Putty

A steel reinforced epoxy putty, this is likely the fastest addition to this list – setting in 4-5 minutes and curing in just an hour, this powerful adhesive gives a whole new meaning to the term ‘quick-fix’. Bonding strongly with anything from metals like cast iron to fiberglass, plastics and ceramic, this versatile putty can even cure underwater, capable of withstanding temperatures up to 500°F, ably waterproof and chemical- and corrosion-resistant. Hardening to a steely rigidity, the putty can be shaped, sanded, filed, painted, drilled and more once it has cured, and is great for filling in gaps for anything from gouges or cracks in metal to chips in rickety furniture.

Because the putty is quick to set and cure, it’s recommended to be mindful of how much you’re mixing and how much time you have to shape and apply the putty. Not suitable for use with rubber, this formula is also available reinforced with copper or aluminum instead of steel, and is totally drinking water safe, meaning it’s a great option to consider for plugging in any leaks in water pipes connecting to faucets and spigots in your home.


Reliance Foundry


Blue Magic


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