How should flux be removed from aluminum that has been gas-welded?

• A. It should be removed by scrubbing it with hot water and a bristle brush.
• B. Use cold water and soap
• C. Soak in solvent
• D. Use a scrub brush with cold water

Answer: (C)

Flux residues left on aluminum after gas welding can be corrosive and foul the surface for inspection, so they must be cleaned thoroughly. Some fluxes used with aluminum welds form residues that are not easily removed with water or scrubbing alone, especially if they’ve baked on or mixed with oils. Using a compatible solvent dissolves and lifts the flux from the surface more completely than water-based washes. Soaking in the solvent allows the residue to loosen and dissolve, making it easier to remove, rinse away, and dry the metal without leaving harmful film behind. After the soak, rinse to remove any solvent and dissolved flux, then dry the area and inspect. This approach is more effective for removing stubborn flux residues than hot or cold water washes or simple scrubbing.