DIY Bronze Welding

Sculptures or other bronze materials may need welding repair.

Bronze is a metal alloy that is composed of copper mixed mainly with tin, but a variety of other metal types may be used. It was used since the earliest times for weapons, tools, building materials and decorative objects. Bronze is still used today for railings, sculptures and musical instruments. Do-it-yourself welding repairs on these products can be challenging because of the wide variety of alloy metals that may be in the material.

Things You'll Need

• Dishwashing detergent or metal cleaner
• Cloths
• C-clamps
• TIG, tungsten inert gas, welder and torch
• Shielding gas, argon or argon-helium mixture
• Filler wire, silicon bronze
• Welding helmet
• Gloves
• Small wire brush

Instructions

1. Clean the bronze item thoroughly with a solution of 1 teaspoon of dishwashing liquid in water to remove grease and oils. A clean surface will provide effective adherence of the materials. Metal cleaners can also be used for this purpose. These products are available at automotive or hardware stores.

2. Secure the two parts together carefully with C-clamps, matching edges in the case of broken parts.

3. Preheat the material with the torch just to the temperature where the metal begins to sweat. This process allows the metal itself to melt the filler material to form the joint. Apply the filler rod to the bronze, allowing the molten material to flow into the joint, and direct it with the tip of the rod. Use small increments of heat to raise the temperature of the material.

4. Direct the angle of the torch to push the filler into the joint recesses. Strive for a continuous weld across the surface to be joined.

5. Allow the weld filler to cool. Check for any gaps or voids.

6. Reheat the material carefully and give the joint a second weld pass, allowing the filler to melt into remaining voids. Avoid applying too much filler to the joint; this can cause cracking. Penetration should be superficial, simply allowing filler to melt into open spaces.

7. Allow the material to cool completely and clean the joint with a wire brush.

Tips & Warnings

• Silicon bronze is generally used for welding bronze materials. However, depending on the composition of the metal, other filler wires may be used, including nickel, phosphorus or tin alloys, according to the Aufhauser website.

• A thinner filler rod is easier to direct than thicker rod.

• Welds done on bronze materials can often crack when dissimilar metals are used. To correct this problem, clean the weld and try a different type of filler rod and reduce penetration of the material into the joint. Different types of filler rod may produce slight variations in color from the original material.

• Bronzes that contain lead are generally considered to be unweldable because they are highly prone to cracking,

• Welding bronze, which contains a high percentage of copper, emits fumes that are hazardous to welders. Copper fumes can cause respiratory irritation and “metal fume fever,” a condition that causes flu-like symptoms. Welders should use a respiratory mask and ensure that the work area is well-ventilated, according to the Government of South Australia website.

References

• Aufhauser: Copper Brazing/Welding Alloys
• Government of South Australia: Metal Fumes
• Esabna: Braze Welding