ER4043 and ER5356 welding rods are both commonly used for aluminum welding, but they have some differences. ER4043 is known for its versatility and is suitable for various aluminum alloys. It has excellent corrosion resistance and produces strong, crack-free welds. On the other hand, ER5356 is best suited for alloys with a higher magnesium content, such as marine-grade aluminum. It offers enhanced mechanical properties and higher strength.