How to Repair Metal: Welding vs Other Methods

Most fabricators go to welding whenever they see cracks or broken metal. It's no surprise, since welding produces an enduring structural bond that resists a range of conditions, loads, and damage.

However, welding is not always applicable. For example, if you need to join dissimilar metals, very thin sheets, or parts susceptible to heat defects, welding won't do a great job.

Luckily, there are several alternatives to welding. In this article, we will discuss the most popular methods for metal repair, including welding and its alternatives. So read on to find out which is best for you.

Most Common Metal Joining and Repairing Techniques

When a metal piece snaps or breaks, that doesn't mean it is over. You can repair most metallic pieces using one of the most common metal joining and repairing techniques, including:

• Welding

• Mechanical fasteners (rivets, bolts, or screws)

• Structural adhesives

• Low-heat thermal joining (brazing and soldering)

Each method has its ups and downs, especially across different metal types, thicknesses, conditions, and costs. Although many prefer welding for its strength, resistance, and load-bearing ability, it is not always applicable.

So, let's discuss further to determine which method is best for your repairs.

Welding: Strongest and Most Reliable Method for Metal Repair

For a long time, welding has been the strongest and most reliable method for repairing and joining two metal pieces. Welding is a relatively inexpensive and fast way to produce a structural bond that resists load, atmospheric conditions, and wear and tear.

The secret behind those strong bonds lies in the working principle of welding. Most popular arc welding methods, such as MIG, TIG, Stick, or Flux-cored welding, create a fusion.

Metal Repair with Arc Welding
Source: https://www.youtube.com/watch?v=844CTBCj7Kw

The heat of an arc melts the pieces and filler metal (if applicable). The filler metal has the same composition as the base metal and fills the gap created by damage, cracks, or weld preparation.

Once the molten puddle solidifies, it creates a uniform bond. Since the filler metal has the same strength and composition as the base metal, the two form a strong connection. Therefore, it is no surprise that many turn to welding when trying to restore the structural strength of broken parts.

When to Use Welding for Metal Repair?

Fabricators use welding to repair metal whenever they need to restore the structural strength of broken pieces. Common applications include fixing cracks and breaks in load-bearing parts, filling holes, or rebuilding worn surfaces.

Matching the strength and load-bearing capacity of the original metal is ideal when:

• Repairing broken or cracked parts: Snapped brackets, torn steel frames, or cracked engine blocks fail when extreme physical, chemical, or thermal forces surpass the metal's strength limits. Repairing them means restoring their original strength, which requires welding.

• High-stress zone repairs: Items that carry heavy weight, pressure, or constant physical force often fail after periodic use. Repairs require welding to regain stress resistance.

• Repairing worn components: Worn-down gears, shafts, or machinery tips are subjected to everyday wear and tear. Repairs often include welding new metal layers.

• Welding missing sections: Patching rusted-out or broken floor pans and panels by fusing new metal pieces.

• General fabrication: You can use welding to repair most metal parts around the home, farm, or ranch. Common examples include leaking pipes, broken door or gate hinges, rusted gutters, or broken patio furniture.

Where Does Welding Fall Short in Metal Repair?

Although it is strong, welding is not always the suitable method for metal repair. Welding has its drawbacks, often inherent to the process. You should look for alternatives in the following cases:

• Metal limitations: Welding is not ideal for all metals, especially dissimilar metal repair. For example, cast iron can be notoriously difficult to weld without cracking. There are often unknown alloys, or pot metal (monkey metal), that mix various metals and can be impossible to repair.

• Low-stress cosmetic fixes: You don't need welding for tiny, surface dings or minor non-structural fills. In these applications, welding can do more harm than good.

• Heat-sensitive, thin metals: Although methods such as TIG work well with delicate and exotic metals, thin sheets are highly susceptible to warping and burn-through.

• Health hazards: Burning certain coating materials, such as zinc, produces toxic fumes. The high heat of the welding arc causes them to boil, creating fumes that can compromise health.

Besides the structural reasons, there are always human factors involved. The welder's skill often determines the strength and quality of the welds. And unfortunately, welding is experiencing a high demand for skilled personnel.

However, manufacturers use alternatives whenever applicable.

Mechanical Fasteners in Metal Repair

In the manufacturing industry, mechanical fasteners were the go-to choice before welding gained popularity. Before self-shielded electrodes, bolts and rivets produced much more reliable bonds in ships and airplanes.

Although much has changed since then, mechanical fasteners remain a practical method for metal repair. They include joining and repairing metals without using heat, which makes them ideal for thin sheet metal prone to distortion or burn-through.

Mechanical Fastening for Thin Sheet Metal Repair
Source: https://www.youtube.com/watch?v=QEu8-lUzMOY

Compared to other metal repair techniques, fasteners are the only solution you can remove if necessary. However, permanent joints can also be achieved through methods such as riveting.

There are several common fastener types:

• Screws and bolts: Typically externally threaded, they clamp metal pieces together. The clamping force compresses the parts together, creating a strong bond. You can remove them later for easy part replacement or regular maintenance.

• Rivets: Permanent fasteners that squash down to form a permanent bond. Unlike screws and bolts, they cannot be removed without deforming or damaging the pieces, but they can create very strong bonds.

• Threaded Inserts and Rivnuts: They add strong, reusable metal threads into thin, soft, or single-sided materials where other screws and bolts fall short.

• Lock Washers and Nuts: Used together or separately to prevent bolted joints from vibrating. They add spring tension or bite into surfaces to hold tight under dynamic loads.

When to Use Mechanical Fasteners in Metal Repairs

Since mechanical fasteners are a fast, easy, and relatively inexpensive method for metal repair, they are used in a variety of applications. You can use them as an alternative to welding in the following cases:

• Repairing parts that need maintenance: Since bolts and screws create non-permanent bonds, they are ideal for parts that require periodic opening, cleaning, and replacement.

• Very thin, delicate pieces: As there is no heat, you can repair heat-sensitive, thin sheets without the risk of burn-through or distortion. Threaded inserts are perfect for thin, soft, or single-sided metal repairs.

• Dissimilar metal welding: You can use fasteners to join dissimilar metals like steel and aluminum. However, isolating hardware is mandatory, as it prevents galvanic corrosion.

• Hazardous conditions and environments: Fasteners are helpful when on-site gas, open flames, or heavy electrical welding equipment create fire hazards or cannot be powered.

• Need quick repairs without putting too much effort: You can use fasteners when you don't have, or don't wanna use, complex welding equipment.

Drawbacks of Mechanical Fasteners

Although advantageous in many applications, mechanical fasteners also have drawbacks. You shouldn't use them in the following metal repairs:

• Fatigue-prone parts and areas: Drilling holes for screws and bolts creates stress concentration points. This is especially concerning under tensile stress, as it drastically lowers the fatigue life.

• Parts requiring high strength: Fastening affects the parts' structural integrity. As a result, fastened joints have much lower strength than welded joints and may fail over time.

• Parts subjected to high temperatures: Extreme heat causes standard fasteners to lose clamp load due to creep relaxation, increasing the risk of joint failure.

• Leak-proof parts and environments: Bolted or riveted patches cannot guarantee a hermetic or pressure-tight seal. Therefore, you cannot use them to repair pressure vessels, boilers, and pipes.

• Increased weight: Bolts, screws, and rivets increase the repaired part's overall weight. While that's not the biggest concern for your everyday repairs, it certainly is an issue in sectors like automotive and aviation.

Structural Adhesives: Quick and Easy Metal Repair Solution

The easiest way to fix some stuff around the house is to super-glue it, but what about metals? Well, advancements in the adhesive industry have brought us solutions that can create bonds as strong as welds.

The best part about adhesives is that they are super easy and quick to use. Unlike rivets, adhesives spread stress evenly and prevent rust. Compared with welding, adhesives don't use heat and can safely join different metals. Most importantly, they can bond more advanced materials such as carbon fiber, glass-reinforced plastic (GRP), or other composites.

Bonding GRP to Steel
Source: https://www.youtube.com/watch?v=22G7U-fA6xI

There are several types of industrial adhesives, but the ones often used in metal repairs are:

• Epoxy (two-component): The most widely used structural adhesive, such as JB Weld. This solution typically uses two components: resin and hardener. As a result, they provide the maximum load-bearing strength among adhesives. In addition, epoxy offers excellent gap-filling and high resistance to heat and chemicals, making it valuable for metal repair.

• Methacrylate (MMA): A subset of acrylics that have an exceptional ability to bond composites and metals. They offer rapid cure times and high tolerance for surface oil or minimal prep.

• Polyurethanes (PU): These combine flexibility with good structural strength. They are ideal for metal parts subjected to vibrations and shock.

When to Use Structural Adhesives for Metal Repair?

The advantages, such as ease of use and strength, make industrial adhesives like JB Weld widely used in metal repair. The common scenarios in which you can use structural adhesives for metal repair include:

• Dissimilar metal repair: Adhesives create a protective barrier that prevents galvanic corrosion when two dissimilar metals come into contact. You can't do that with welding or fasteners without insulating hardware.

• Super thin or lightweight sheets: Adhesives can create a firm bond between heat-sensitive, delicate metal sheets. You limit the risk of welding heat damage and of over-bolting or over-riveting the sheets.

• Parts needing even stress distribution: Structural adhesives evenly distribute physical loads across the entire bonded surface. There is no single-point stress concentration like with fasteners or welds. Even distribution is also helpful for joints subject to heavy vibrations, as they shock-absorb better than welds or rivets.

• Fulfilling aesthetic requirements: Adhesives leave the exterior smooth and clean, without visible weld marks, distortion, or protruding rivet heads.

When to Move From Adhesives in Metal Repairs?

Like other methods, adhesives are not applicable in every metal application. The method falls short in the following situations:

• Parts subjected to high peel or cleavage stress: Adhesives do not provide enough strength for joints designed to pull straight apart rather than handle shear or compression loads.

• High- or low-temperature applications: Most adhesives weaken at extreme temperatures. Most formulas weaken above 250°F, or stop curing below 45°F.

• Not suitable for primary structural members: Most fabricators will advise against using adhesives for structural parts such as critical heavy-duty frame components, core suspension parts, or major structural panels.

• Parts with poor surface conditions: Most adhesives (except MMA) require immaculate surface preparation before joining. Any oil, grease, rust, or dirt can weaken the bond.

• Immediate repairs: Most formulas take hours to set and cure. For example, JB Weld needs 4-6 hours to set but fully cures in 15–24 hours. If you need your broken parts immediately, look for a different method.

Brazing and Soldering: Low-Temperature Alternative to Welding

Brazing and soldering are low-temperature techniques that use just enough heat to melt the filler metal, without melting the base metal. Tight part fit-up draws the molten filler into the joint (capillary action), forming a bond.

The main difference between brazing and soldering is in process temperature:

• Soldering uses temperatures up to 840°F, making it ideal for delicate tasks such as electronics, piping, and wiring.

• Brazing runs hotter, over 840°F, but it still doesn't melt the base metal. It creates stronger bonds, ideal for metal repair.

The main advantage of brazing and soldering is that they don't melt the base metal. As a result, they are suitable for delicate and heat-sensitive metal repairs and tasks.

When to Use Brazing and Soldering in Metal Repair?

Due to low temperatures, soldering is best suited for low-stress, heat-sensitive tasks such as:

• Electronics: Broken wires and cables, components, and circuit boards.

• Light plumbing: Repairing leaking low-pressure copper pipes.

• Delicate craft: Jewelry repairs or stained glass.

• Any low-heat application: Repairs for metals that can deform under the high heat of the joining process.

Soldering a 1/2-Inch Copper Pipe
Source: https://www.youtube.com/shorts/Frgq-lGwqqA

Brazing creates stronger bonds, so you can use it to repair:

• HVAC and refrigeration: Fixing higher-pressure AC systems and copper tubing exposed to higher stress.

• Dissimilar metals: Joining brass to stainless steel or copper to steel.

• Higher-strength joints: Repairing parts that require a durable, load-bearing bond, but can fail due to the high heat of welding.

• Delicate structural components: Lawnmower parts or metal fittings that face moderate mechanical strain.

When to Avoid Brazing and Soldering in Metal Repair?

Although advantageous in many ways, brazing and soldering are not suitable for specific repairs, such as:

• Load-bearing frames and parts: The strength of brazing cannot withstand stress in vehicle frames, trailers, or heavy machinery.

• Thick metal sections: Molten filler cannot penetrate as deep as a welding arc or hold the mass.

• High-temperature applications: High heat can melt the brazed or soldered joints, making them unsuitable for parts near engine exhausts or industrial furnaces.

• Harsh environments: Harsh chemicals can eat away the softer filler metal while leaving the base metal intact.

• Cosmetic applications: Bonds don't always match the exact base metal color and grain for cosmetic or restoration reasons.

Final Thoughts

Welding is, without a doubt, the strongest and most reliable metal joining and repair technique, needed whenever you need to restore the structural strength of pieces. However, it has its drawbacks, so understanding its fundamentals and alternatives is crucial.

Go for welding if you need strong, load-bearing bonds that withstand harsh conditions. Repairs are long-lasting, but it falls short on heat-sensitive, delicate, and dissimilar metals.

Choose mechanical fasteners when repairing delicate, thin sheets and parts that require maintenance. Bolts, nuts, and rivets create strong bonds with little effort, but they also create stress points.

Go for adhesives if you need a quick, easy solution for various, dissimilar metals. Industrial adhesives create strong bonds, but they fall short under pressure and extreme temperatures.

Brazing and soldering are low-heat alternatives that don't melt the base metal. They are excellent for delicate, heat-sensitive metals, but weak in load-bearing and high-temperature applications.

🧐 How to Repair Metal: Welding vs Other Methods FAQ

1. How Do I Know Whether to Repair or Replace a Damaged Metal Part?

Replace the part if it has extensive corrosion, severe deformation, repeated cracking, or significant material loss. Repair is more practical when the damage is localized and enough sound metal remains to support a reliable joint.

2. Can Rusted Metal Be Repaired Without Welding?

Yes. Minor, non-structural rust damage can sometimes be repaired with structural adhesive and a metal patch or mechanical fasteners. Perforated load-bearing metal usually requires the weakened section to be removed and a new piece welded in place.

3. Can Structural Adhesives and Rivets Be Used Together?

Yes. Adhesive bonding and riveting can form a hybrid joint that combines even stress distribution with immediate mechanical support. The rivets can also hold the parts in position while the adhesive cures.

4. Does Brazing Weaken the Base Metal?

Brazing usually causes less distortion than welding because it does not melt the base metal. However, its heat can still soften heat-treated alloys, damage protective coatings, or change the properties of thin components.

5. How Can You Check Whether a Metal Repair Is Strong Enough?

Inspect the repair for cracks, gaps, loose fasteners, incomplete bonding, or visible distortion. Non-critical parts can be loaded gradually, but safety-critical repairs may require professional inspection or nondestructive testing.

6. How Long Should You Wait Before Using a Repaired Metal Part?

It depends on the repair method. Welded and brazed parts should cool and be inspected before loading, while structural adhesives must reach their specified full-cure time—not merely their initial setting time.