Galvanised U bolts not only last longer, they look smart and are aesthetically pleasing.
5/8" U Bolts are often used on single axle loads approx 1500kg and above. Almost mandatory on Off-Road springs.
5/8" x 6" Galvanised Plated U Bolts have been Static Load tested to break at 25t per, Safe Working load of 5t (10t per axle)