I think your normal map is inverted, it should be more like this: https://thumbs.dreamstime.com/z/metal-surface-texture-dirty-diamond-used-anti-slip-design-51773078.jpg
I think your normal map is inverted, it should be more like this: https://thumbs.dreamstime.com/z/metal-surface-texture-dirty-diamond-used-anti-slip-design-51773078.jpg