I'm using Blue Demon welding rods to repair a broken outdoor lamp post. I tried to use my TIG but the cast aluminum was of such poor quality it would not weld. I ended up using the brute force approach for this repair. While not the prettiest welds they are acceptable for this type of repair when all else fails.

Blue Demon Arc welding Rods: https://amzn.to/2lOQGDO