Which of the following is a common issue when welding aluminum?

Aluminum is known to develop a thin oxide layer on its surface when exposed to air. This oxide layer forms very quickly and can significantly impact the quality of the weld if not removed before welding. The oxide has a melting point that is significantly higher than that of aluminum itself, meaning that it can prevent proper fusion during the welding process. If the oxide is not cleaned off, it can lead to weak welds that may not bond correctly, resulting in defects such as porosity or lack of penetration.

Understanding this common issue highlights the importance of surface preparation in aluminum welding. Proper cleaning methods, such as using a suitable solvent or mechanical means, are essential to ensure a sound weld. This concern distinguishes aluminum welding from other materials where oxidation is less of an issue or does not occur as readily.