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Can I Use JB Weld to Repair Aluminium?

Date: 15-02-2024
TIG Welding MIG Welding DIY

Can I Use JB Weld to Repair Aluminium - Alphaweld

In short – yes, you can use J-B Weld to repair aluminium. 

But the question is, what is the extent of the needed repair, and are you repairing something critical that can endanger you or someone else if the bond were to fail? 

Unlike real fusion welding, J-B Weld does not melt and fuse two metal pieces. That's a critical distinction from actual welding. While J-B Weld can create a really strong bond, you should consider many variables when deciding to use an adhesive to repair metals.

How J-B Weld Works

J-B Weld is a two-part epoxy system that creates a strong bond between adhered surfaces when used according to the product instructions. The two parts need to be mixed at a 1:1 ratio, applied to both parts and left to cure for about 15-24 hours. The created bond is solid and can be sanded, drilled, moulded, and tapped. 

In our opinion, you can definitely use J-B Weld to make less extensive repairs on aluminium in non-structural applications. Small cracks, fissures, and holes can be repaired with J-B Weld. You can even repair engine parts like flanges, manifolds, water pump blades, and other cracked or broken engine components. 

However, you are more likely to make a permanent repair with fusion welding. The J-B Weld is a quick solution to avoid the welding process, but it does not fuse the two materials. So, even if the produced bond is powerful, you will get better results when fusing materials with an arc welding process. 

JB Weld - Alphaweld

What is Fusion Welding?

In fusion welding, two metal pieces are brought to the molten state and fused together with or without a filler material. MIG and TIG welding are the two most commonly used fusion welding processes for aluminium. We recommend both for making lasting aluminium repairs on cracked engine parts, aluminium boat repairs, structural components, pipes, flanges, manifolds, valves, and other critical repairs. 

Fusion arc welding produces far greater strength than adhesion by J-B Weld and similar epoxy methods. For example, the AWS D.12 Structural Welding Code for aluminium specifies a 40,000 PSI (40 KSI) tensile strength for welded 5083 sheet and plate aluminium alloy. That's a frequently used aluminium, but there are of course many other alloys you can encounter. However, J-B Weld advertises a 5020 PSI tensile strength after curing, which is eight times weaker than the example of the 5083 alloy. Some aluminium alloys will provide lower tensile strength upon welding, but all aluminium alloys have a higher tensile strength than 5020 PSI if welded properly. 

MIG Welding Aluminium

The MIG welding process is faster and easier to perform compared to TIG welding, making it a better choice for the majority of applications. The MIG welding process uses a semi-automated wire feeding system that guides a filler metal wire through the MIG welding gun and into the welded joint. The wire is energised and acts as a filler metal and an electrode at the same time. So, when the wire comes in contact with the welded metal it creates an electric arc, which melts and fuses the material into a solid joint. This is a gas-shielded process. So, you need a shielding gas to prevent the atmospheric contamination of the weld pool. The gas is also supplied automatically via a MIG gun after you press the trigger. For aluminium, you need a 100% argon gas bottle.

The Unimig VIPER 185 is a multi-process welder that supports MIG, TIG, and STICK welding processes. It's straightforward to set up, outputs up to 180A for MIG, and weighs just 12 kg. There are many aluminium wires you can use, depending on the welded alloy. But a good general-purpose MIG wire is the Betaweld ER5356. You can read more about MIG welding aluminium in our separate guide.

Unimig Viper 185 - Alphaweld


TIG Welding Aluminium

Like MIG, TIG is also a gas-shielded arc welding process, and it also requires a 100% argon gas bottle for TIG welding aluminium. But, unlike MIG, TIG is slower and more difficult to learn and apply. However, the TIG welding process is irreplaceable for high-accuracy welds, especially those where aesthetics are critical.  

The TIG welding process uses a non-consumable tungsten electrode. The electrode never touches the material (when using HF start), so the material never receives any inclusions. MIG wire acts as an electrode and can introduce a small number of impurities in the weld. But TIG doesn't do this. TIG is an exceptionally clean process where the electric arc jumps from the tungsten electrode to the joint, allowing you to manually add the filler metal or weld without it. We wrote a separate blog on the differences between MIG and TIG welding.

However, we recommend MIG for beginners and TIG for high-accuracy applications. The VIPER 185 we mentioned earlier supports DC TIG, which cannot be used for welding aluminium. You need AC TIG output to TIG weld aluminium. For example, the Unimig RAZOR TIG 200 AC/DC welder supports the AC TIG output, allowing you to weld aluminium. 

Unimig RAZOR TIG 200 - Alphaweld


The reason why AC is necessary for aluminium is the presence of surface oxides on aluminium that can only be broken by the positive side of the AC cycle, while the negative side handles the weld penetration. So, DC TIG welding aluminium would not give quality results.

Should You Weld the Aluminium or Repair it With J-B Weld Epoxy?

If you need to repair anything structural or critical for safety, we highly recommend using a fusion welding process. Likewise, if your engine parts or some machinery element is broken and you need to make a lasting repair, we recommend welding it. 

On the other hand, if you are making a small repair on your car, kitchenware, home items, furniture, farm equipment, and other less critical equipment, we believe you can save time and effort by using J-B Weld. It's important to note here that J-B Weld says that their products are not rated food-safe, so it's not recommended to use on areas in direct contact with food. You can find J-B Weld at Bunnings and general hardware outlets.

Need More Help Choosing a Welding Method for Aluminium?

If you need additional help choosing a welding process, shielding gas, or filler material for aluminium, contact the experts at Alphaweld - call (08) 9456 8000 or send us an online enquiry and we'll be happy to assist.