What is the minimum distance that paint must be removed from the root of the weld when welding on a structure?

The minimum distance for paint removal from the root of the weld is specified to ensure that the weld area is free from contaminants that could adversely affect the quality and integrity of the weld. In the context of the AWS D1.1 Structural Welding Code, removing at least 2 inches of paint from the root of the weld provides a sufficient margin to ensure that the underlying metal is clean. This practice helps prevent issues such as porosity and inadequate fusion, which can arise when welding over painted or coated surfaces.

The removal of paint is crucial as coatings can impede heat transfer, lead to poor weld penetration, and introduce impurities that compromise weld strength. It's important for welders to adhere to this guideline to maintain the integrity of the welded joint and ensure compliance with the code's specifications.