PC-7 Epoxy Vs. JB Weld: any difference?
Compared to JB Weld, PC-7 is noticeably thicker and can’t be shaped as easily. However, it provides superior bonding strength, especially on metal surfaces after oil/residue is properly cleaned. For metal-to-metal bonding, PC-7 outperforms JB Weld hands down.

PC-7 Epoxy Vs. JB Weld: Specs & Uses
⏰Cure Time
PC-7 Epoxy: 20-25 minutes (initial set), 24 hrs (full cure)
JB Weld: 4-6 hrs (initial set), 15-24 hrs (full cure)
🆚Limitations
PC-7 Epoxy: For small repairs only, not intended for structural or heavy-duty applications.
JB Weld: Not ideal for flexible materials or plastics.
🛠️Common Uses
PC-7 Epoxy seals small cracks in hydraulic oil tanks or other metal surfaces; can be used to restore steering wheels made of plastic; repair and reinforce golf club heads; Rubber-to-Metal Bonding.
JB Weld can be used to block cracks between engine cylinders; repair small punctures and leaks in older aluminum boats; patch exhaust leaks, especially at the point where a donut goes flanges off the manifold; reunite broken plastic parts, such as a clutch handle or a turn signal lever on a motorcycle or car.
Technical Info
My Hands-on Test of PC-7 Epoxy

✅Pros: PC-7 Epoxy
First off, let’s talk shelf life. Straight out of the tube, this epoxy paste can last 2+ years without issue. In fact, I’ve mixed and successfully used PC-7 that was over 5 years old, though the paste was a bit drier than newly purchased product.

I’m demonstrating how to properly repair minor surface rust on a car fender using PC7 filler. First, I hammered down the rust and grind it smooth. Then I applied the PC7 filler to fill the damaged area, which will permanently repair the rust. This only works for minor surface rust, not major rust repairs, which require welding in new metal.
Paintable
PC-7 can be painted once it’s fully cured. Just be sure to sand it smooth first and avoid heat-sensitive paints if using it on surfaces that expel a lot of heat.

The cured hardness is very impressive – about the same as a golf ball. Extremely tough, but not quite metallic hard. It does take around a week to reach full hardness though. After 24 hours it’s 95% cured but can still be slightly dented. That final 5% takes another week to fully harden.
Seal Small Cracked Welds in Hydraulic Oil Tanks
I’ve used PC-7 to successfully seal small cracked welds in hydraulic oil tanks where welding wasn’t an option. Just make sure the area is thoroughly cleaned first. It truly bonds to almost any material – metal, cement, rubber, plastic, you name it.
Bonding Surfaces
Speaking of plastic, it works great for bonding plastic parts. The fully cured epoxy is essentially like hardened plastic itself. Safe for use on plastic items.
Now when bonding very smooth surfaces like painted metal, roughing up the surfaces first is recommended for maximum adhesion. But PC-7 will still bond admirably to many smooth surfaces.
For applications needing some flexibility, like bonding rubber to a bicycle frame, this may not be the best option as it does cure into an incredibly rigid bond. But the forming ability before cure allows shaping as needed.
Compared to the PC-11 marine epoxy, PC-7 has a longer working time before hardening which is very useful for larger jobs. It’s truly the “tough job” formula made for maximum bonding strength.
PC-7 would work well for securing metal anchors in concrete, installing undermount sinks (though not ideal for future replacements), sealing pinholes in oil pans, bonding butcher block to counters, and more. Its bonding power is truly impressive.
Heat resistance is excellent. You can use it on hot vehicle components, lawn equipment repairs, and it won’t break down. Just let it fully cure first.
For bigger jobs like bonding 20 road reflectors, two tubes should be enough product. Just be sure to prepare and roughen the surfaces properly first.
❌Don’t expect it to be a flowing liquid
Right after mixing, it has a very stiff, paste-like consistency that holds its shape well. Don’t expect it to be a flowing liquid. And it does not expand or shrink much at all as it cures.

FAQ of PC-7 Epoxy
Q: How does PC-7 Epoxy compare to JB Weld?
A: In terms of thickness, this product is thicker than JB Weld, making it a bit challenging to shape easily. Additionally, it is not suitable for flexible surfaces as expected for epoxy. However, apart from these differences, it performs almost on par with JB Weld.
Q: I have some very small cracked welds in a hydraulic oil tank. Can PC-7 Epoxy seal them, considering welding is not an option?
A: To seal the cracks, you need to ensure that the tank is empty below the holes and clean any oil residue from the area around the holes. Using a good degreaser like Dawn is recommended. Then, mix the best epoxy for metal gas tank repair – PC-7, which has a tar-like consistency, and apply it to seal the holes. This method has proven successful in sealing holes in various objects, including an oil pan on my truck. It works great.

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What Is JB Weld

✅Works Amazingly for Lower-Stress Applications
I’ve used JB Weld to attach a high-pressure 2000 PSI power washer nozzle that had the wrong threading. After letting it fully cure, that repaired threaded connection handled the intense water pressure like a champ. While I wouldn’t rely on it for something as extreme as a gun barrel’s chamber pressures, JB Weld works amazingly for lower-stress applications.
One of my favorite uses is bonding dissimilar metals like aluminum to brass. JB Weld doesn’t actually fuse the metals together, but it essentially becomes an ultra-strong epoxy adhesive that permanently bonds the two surfaces. I’ve repaired aluminum oil pans this way by JB Welding new threaded brass drain plugs into place.
The epoxy adheres tenaciously to aluminum in general, which has come in handy for patching holes in gas tanks and other aluminum components. I just rough up the area with 80 grit sandpaper, clean it thoroughly with isopropyl alcohol, apply the JB Weld quickly before oxidation occurs, and I have a permanent aluminum repair.
Good for Insulation
The dark gray colored epoxy won’t conduct electricity, which is good for insulating purposes. It also won’t impart any sort of taste if using it for non-food contact repairs. I’ve successfully reattached emblems, badges, and trim pieces back onto cars and equipment using JB Weld.

❌Don’t expect it on surfaces with extreme heat
While JB Weld works on most materials, there are some exceptions like lead metals and surfaces that will see extreme heat. You can’t use it on cast iron cookware that will go over 300°F or in direct oven heating over 500°F as it will degrade. But for cooler applications, whether it’s bonding vertical tile to a metal backsplash or repairing ceramic, concrete, carbon fiber, or plastic components, this cold weld putty is magic.
💬 FAQ of JB Weld
Q: Would JB Weld be considered electrically conductive?
A: No, it is not electrically conductive. We have mentioned it in is jb weld conductive already.
Q: Can I use JB Weld to repair small punctures and leaks in an older aluminum boat?
A: This is a general-purpose epoxy that worked great for me on cast iron. It says that you can use it for marine purposes, but you might also consider using a boat life caulk or specific product made by JB-Weld that is designed for water.
Q: Is there a way to remove the hardened JB Weld or soften it once it has hardened?
A: You could try using 747 adhesive remover. It dissolves many types of hardened epoxies, and one of the reviewers in those listings specifically said it worked on JB Weld. However, please note that (1) you need to soak your item, you can’t just brush Attack on it, so this will only work for small items; (2) make sure Attack won’t dissolve your parts; and (3) be sure to read the comments and safety instructions and pay attention — this is seriously toxic stuff.
What is the expected lifespan of PC-7 Epoxy (without mixing different substances)?
According to the datasheet, the shelf life is stated as 2 years or more. Personally, I have successfully used the PC-7 that I had for over 5 years, and it still worked fine. However, I noticed that the paste seemed slightly drier during mixing compared to the newly purchased PC-7.