Avoiding porosity when welding aluminum
Porosity is a common problem when welding aluminum that has not been properly prepared. It is often caused by the presence of trapped contaminants in the porous layer of aluminum oxide on the metal’s surface. For the best results, this layer and any associated contamination must be removed prior to welding. This can be done in three simple steps:
- Degrease: Use acetone or denatured alcohol and a lint free rag to remove any hydrocarbons and moisture that may be present on the surface.
- Mechanically remove the oxide: This can be accomplished by scraping, cutting or milling without cutting fluids or by using a clean stainless steel brush. (Never use an abrasive. Most are made from aluminum oxide itself and all can leave foreign material imbedded in your base metal)
- Degrease again: Repeating the process of step 1 will take care of any remaining oils that may be present.
*ALWAYS store flammable substances safely away from the weld zone and be certain any degreasing agents have fully evaporated from the workpiece before you begin welding.
*NEVER use any cleaners or degreasers that contain chlorine or chlorinated hydrocarbons in or near your weld zone. Harmful chemical compounds can be released when such cleaners are used in conjunction with welding processes.