How far from the root of the weld must the base metal surfaces be cleaned of foreign matter before welding?

Cleaning base metal surfaces before welding is crucial to ensure a strong, defect-free weld. The requirement to clean the surfaces of foreign matter, such as paint, oil, rust, or other contaminants, extends a specific distance from the root of the weld. This distance is typically prescribed to guarantee that the heat input during the welding process effectively penetrates and bonds the base metals, and that any potential contaminants that could lead to weld defects are removed.

The correct answer specifies a distance of 2 inches, which is a standard practice in welding procedures. Cleaning a 2-inch area around the weld root helps ensure that the weld metal has a clean interface for better adhesion and minimizes the risk of defects such as porosity, inclusions, or weak points that could arise from foreign matter left on the surfaces.

The other choices, while they suggest important considerations in cleaning, either under-represent or over-represent the necessary distance deemed effective for achieving optimal weld quality based on welding standards and best practices.