What best suited electrode is used to weld on rust or paint?

The best-suited electrode for welding on rust or paint is typically a low-hydrogen electrode, such as E7018 or E6013. These electrodes are designed to provide a stable arc and good penetration, which helps to burn off contaminants like rust and paint. Additionally, they can produce a strong weld despite the presence of surface impurities. However, for optimal results, it's always recommended to clean the surface as much as possible before welding.