How Epoxy Works and What Do You Use it For?

Epoxy can be considered a bit of a blanket term for a bunch of different names you may have come across – epoxy resin, paint, coating, to name a few. Because of its versatility and innumerable applications, what this substance is and how it is used varies in the many industries it has become a mainstay in, for anything from laminating plywood to shipbuilding and naval engineering.

So what really is epoxy, and what makes it such a multipurpose substance? To begin understanding it, let’s break down the science behind the substance.

A couple of terms

Before launching into the chemistry of it, we’re going to explain a few terms and concepts that’ll pop up in our explanation, to simplify understanding and avoid making this into too much of an arduous classroom session.

For starters, let’s begin with the definition of epoxy. Bright Hub Engineering describes it as a “thermosetting polymer” – ‘thermosetting’ describes a substance that permanently sets or hardens once heated, while ‘polymer’ refers to a large molecule, made of a chain of monomers, a sequence of repeated and similar subunits. Polymerization, then, refers to a chemical reaction where several monomers come together to form complex, 3-dimensional polymer structures. Epoxies are also described as a ‘resin’ – viscous liquids which can be thermoset into permanent solids.

So what exactly is epoxy?

Epoxy is essentially a substance formed through the polymerization of monomers called epoxides. Typically, epoxies have two components – a resin and a hardener, which when combined undergo a chemical reaction which transforms from a thick liquid to a rigid solid, creating closely-linked cross-polymer structures. The two components need to be mixed in specific ratios, and as they begin to react they start to cure. The reaction generates heat, which thermosets the liquid to a tough, solid plastic, though additional heat can be applied to make the substance cure faster.

However, single component epoxies also exist – in such cases the substance is cured at high temperatures, instead of requiring a hardener, between 250-300°F, to create an extremely strong, durable and resilient solid, so much so that it is often used as an alternative to welding.

Because of these properties, epoxy is widely used in adhesives, protective coatings, priming and more. They’re strongly resistant to chemicals and temperature changes, are great insulators, have versatile mechanical strength and durability, and powerful adhesive strength, to name just a few properties. Epoxies can also be adapted to enhance certain properties, like increased temperature resistance, to be used in specialized environments, including underwater. Speaking of which –

Application and uses of epoxy

With its wealth of properties and impressive usage ranges, it’s not surprising that as well as being essential to several industrial applications, it’s also a handyman’s favorite at home. Here’s a breakdown of just a few ways epoxy can be used.

Furniture repair & carpentry

Because of its powerful adhesive quality and durability, epoxy can be used to fill up gaps, the liquid pumped in through a handyman syringe into the joint of a loose-fitting table leg or stand, curing naturally until its hardened enough to turn rickety pieces of furniture around your home into sturdier, stronger and more durable items. This is a great solution for tackling wood rot, or to fill in gaps in metal or plastic structures – once cured, the structure will once more be robust and sturdy thanks to the rigid and extremely durable plastic holding everything together. Subsequently, you’ll find great use of epoxy adhesives in woodworking too, as an alternative or complement to wood glue.

Epoxy putty is also a great solution to fill out chipped areas on furniture – moldable and with the thermosetting properties making this a great adhesive, you can fit a section of the putty over the damaged or missing area of your chipped furniture, allow it to cure, chip off the excess and sand it over for good-as-new surfaces.

In fact, because of the tightly linked bonds and low porosity of epoxy once hardened, it’s great for coating surfaces which tend to be exposed to liquid often, like kitchen islands and bar countertops.

Floor paint & coating

If done right, epoxy floor paint is a fantastic, wear- and tear-resistant, easy to clean and maintain option for garage floors. It’ll resist grease, stains, cracking, chemicals, and temperature and weather changes, as well as coping with your cars moving over it.

Floors can also be laid with epoxy as an adhesive tightly holding together quartz and aluminum oxide grains. The result is highly durable and wear-resistant.

Mechanical applications

Epoxy can be used for anything from reinforcing metal bolts to hold heavy machinery stationary, prevent corrosion and keep stress-induced cracks from emerging, to an alternative for welding. At home, epoxy glue may even be handy to attach pieces of metal together if you don’t have the experience and/or the equipment for soldering. Industrially, the thermosetting properties of epoxy and the ability to control how fast it can cure often make it a more favorable alternative to mechanical assembly – not only do you get powerful cohesion, the resultant solid is weather, temperature and chemical resistant, protects metal components from corrosion, and can resist stress and vibration to last longer.

Note though that epoxy should not be used on galvanized metal, as it may peel off. It is a good alternative for use on aluminum, though, which is not suitable for galvanization due to its tendency to bend.

Things to note

If you’re attempting to use epoxy at home, especially for the first time, it is important to follow the manufacturer’s instructions to a T. Remember that you shouldn’t use epoxy adhesives and substances in a closed space – the vapors can be dangerous, and your work-area needs to be properly ventilated so you don’t end up steeping in the noxious fumes. Check and double-check the recommended ratios for resin and hardener if you’re using a two-component epoxy, and familiarize yourself with the curing process – some epoxies cure faster than others so you’ll have to be quick and sure-handed during application.

It’s also important to acquire all the materials you’ll be needing, to hold and mix two-component epoxy, or to apply it. If you spill epoxy on yourself, clean it off with vinegar. Acetone can be used to clear up surfaces, but can be poisonous for use on skin since it can absorb into your system and lead to acetone poisoning. It’s always useful to wear protective gloves when working with epoxy, just in case.

Lightweight and highly malleable and ductile, aluminum is a pretty big part of our everyday lives, whether or not we always notice it. From cook-ware to appliance components to wiring to a popular material for structuring boats, it’s an essential everyday metal, diverse in use and resistant to corrosion. But imagine finding a hole in your favorite aluminum cooking pot, or a leak around the metal fastening attaching your garden hose to the spigot. A tiny crack, the smallest bit of damage, and the whole thing becomes unusable. But rather than having to resign yourself to throwing out an otherwise well-built piece of homeware, hardware or any of the multitude of aluminum-constructed objects our lives are strewn with, consider the possibility of repair – patching together the hole, filling in a crack, solidifying a loose screw or bolt so you don’t run the risk of it coming off again.

Run-of-the-mill adhesives like superglue aren’t going to cut it – no, when it comes to heavy-duty adhesion, we’re talking about epoxy, probably the godfather of adhesives when it comes to bonding strength, durability and resilience. The right two-component epoxy, or even some epoxy putty, may just be what you need to plug a hole in your aluminum canoe, stick loose pot handles back on such that they’ll hold for life, or reattach decorative metal pieces together without the risk of them coming apart. A great versatile, if not necessary, addition to our toolboxes, here are our picks for the best epoxy for aluminum.

KEN’S PICK
J-B Weld 8272 MarineWeld Marine Epoxy

As the name suggests, this adhesive is specially formulated for contact with water, making it a great choice for the boating and water-sport enthusiasts amongst us. Rather than having to break out the heavy (and expensive) artillery to fix a couple of leaks and holes, this inexpensive two-component epoxy easily fills in gaps, setting in 4-6 hours at ambient temperatures and curing to a becoming dark gray in 15-24 hours.

The adhesive is waterproof, and resistant to chemicals and petroleum, and within a minimum of 15 hours can hit the water again, versatile and convenient enough to use for anything from repairs to your hull or deck, to fixing up components of engines, not just of a boat but for other vehicles as well. In fact, this 1:1 ratio epoxy works just as well for quick-fixes to leaky rain gutters, clothes tubs, or other metal bits and bobs coming into contact with water often. Also brilliant for non-water-contact usage, the adhesive has a tensile strength of 3,960 PSI. Once the adhesive has cured, it can be filed, sanded, painted, drilled or otherwise shaped as you need it.

KEN’S BUDGET PICK
J-B Weld 8265S Cold Weld Steel Reinforced Epoxy with Hardener

For the ridiculously pocket-friendly price, this two-component epoxy packs a big punch – you’ll get exponentially more payoff thanks to the number of applications for this versatile adhesive. For anything from engine repair to secure a head gasket into place to mending weld breaks on metal frame furniture, this powerful adhesive with a tensile strength of 3,960 PSI is going to hold out for you through thick and thin. Resistant to chemicals, temperatures up to 550°F, water, petroleum and acid when fully cured, the 1:1 ratio adhesive sets in 4-6 hours and cures within 15-24 hours, darkening to a dark gray color.

Because of its extreme durability, resilience, low-porosity, wear-resistance and high adhesive ability, this two-component epoxy is a great alternative for mending broken welding, gluing metal elements together, fixing holes and leaks and reattaching broken or loose metal parts of appliances and hardware, prolonging the use of anything from an aluminum pot with some holes that need filling or cracks in a window pane letting out the cool of your air conditioning. As with our previous instalment of the same brand, the adhesive can be sanded, filed, shaped and painted as you need it once it has cured.

RUNNER-UP
Marine-Tex Epoxy Putty White 2 Ounce Kit

Sometimes, you’ll be fixing more than a few small leaks in an aluminum boat – wide cracks, large holes or bolts holding brackets, mounts and platforms into place coming loose, could all do with some help from this brilliantly adaptable, easy to use epoxy putty. Of a thick, creamy consistency that is easy to mix (using 5 parts resin with 1 part hardener) and apply, curing in 24 hours at a constant temperature of 72°F to a rigid steel-hard solid ideal for permanent adhesion, installation and repairs, this epoxy putty is heavy-duty enough to be a go-to alternative for mechanical applications like welding. With a powerful tensile strength of 4,000 PSI, the putty is available in white and gray, with different compressive and adhesion shear strengths for each color, the white option suitable for being tinted depending on your color needs.

As the ‘Marine’ in the name implies, the putty is waterproof and the perfect choice for filling in and repairing damage to aluminum components in frequent contact with water, as well as reattaching loose or stripped fasteners, reinforcing bolts, permanently attaching dissimilar metal elements without galvanic corrosion occurring, and filling in chips or gouges in not just metal but also wood and fiberglass. Highly resistant to temperature, chemicals, wear and tear, the putty is perfectly suitable for being sanded, tapped, drilled, shaped and so on post-curing.

Note, though, that while the putty is great for bonding together metal components, it does not work as well with polypropylene and polyethylene plastics.

RUNNER-UP
Permatex 84109 PermaPoxy 4 Minute Multi-Metal Epoxy

Another two-component adhesive, this versatile epoxy has an impressive tensile strength of 4,500 PSI, intuitive to use and heavy-duty enough for multi-piece assembly and metal-to-metal adhesion. Perfect for reinforcing and repairing welding, filling up cracks in metal, and attaching metal fastenings, the adhesive sets in 4 minutes and cures to a dark gray color in roughly 24 hours. Once cured, the adhesive can be drilled, sanded, filed, shaped and painted as you need it. This 1:1 mixing ratio epoxy can be used for anything from mounting metal components to putting an aluminum utensil like a colander or baking tray falling apart back together again, for many more years of use. This epoxy is not only great for aluminum, but works just as well with brass, copper, iron, stainless steel and other metals too.

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