Welding Prep for Aluminum
Welding prep for aluminum is essential to ensure a proper weld while maintaining the integrity of the metal. Proper prep protects the metal from burns and from inadvertent melting given the high heat conductivity of aluminum. Preheating the aluminum can be the most difficult aspect of welding prep given the heat conductivity of the metal and its tendency to warp and shrink under intense heat, but the rest of the prep process is fairly easy for do-it-yourselfers.
Things You'll Need
- Hydrocarbon-free degreaser
- Stainless steel wire brush
- Vise grips or clamps
- Aluminum or copper blocks or bars
- Propane torch
- Infrared thermometer
Instructions
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Use a hydrocarbon-free degreaser to remove cutting solvents, oils, aluminum oxide and other contaminants from the surface of the aluminum. Some aluminum comes from the factory with a coat of oil for ease in stacking and separating several sheets of aluminum. Contaminants will prevent the filler metal from adhering to the aluminum during the weld.
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Use a stainless steel wire brush to further bristle and remove cutting solvents, oils, aluminum oxide and other contaminants from the surface of the aluminum. Move the wire brush in only one direction when cleaning the aluminum to avoid creating irregularities in the metal and to maintain a flat surface on the piece of aluminum. Use light strokes when bristling the aluminum with the wire brush to avoid embedding oxide and rust further into the aluminum. Do not use a brush that you use on other metals because this can further contaminate the surface of the aluminum. Use water to rinse any residue from the aluminum.
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Use vise grips or clamps to hold the piece of aluminum in place over a heat sink of copper or aluminum bars or blocks. The heat sink will help distribute heat throughout the piece of aluminum during the preheating process to prevent shrinking and warping.
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Preheat the aluminum before welding to prevent it from cracking under the heat of the weld. Use a propane torch and point the flame at the heat sink near the aluminum. Do not aim the propane flame directly onto the aluminum because this can damage the metal. Use an infrared thermometer to check that the preheating temperature remains between 230 degrees Fahrenheit and 500 degrees Fahrenheit.
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Begin welding the aluminum within eight hours of prep to prevent the further accumulation of contaminants.
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Tips & Warnings
Do not preheat aluminum that has been heat treated because this will soften and damage the metal.
References
- Photo Credit welding image by glgec from Fotolia.com
