Ductile iron and grey cast iron trench grates are inexpensive, hardy, long wearing choices that offer many decorative possibilities due to the material's castability.
Grey Cast Iron Grates
The properties of grey cast iron make it the most common material used by municipalities for grates and manhole covers. Most cast iron in these situations are known as gray irons. Like steel, gray iron is incredibly strong. Compared with steel, it offers greater vibration damping, which can be useful in hardscape where traffic vibration may affect concrete. Cast iron also does not deform under compression. It's solid even under a heavy load.
Ductile Iron Grates
Ductile iron grates are very similar to cast iron grate options with only a few differences. Selecting between the two depends upon the application and drainage system needed. The main difference is that ductile iron grates contain graphite that increases their flexibility. They can withstand extreme colds and not break compared to cast iron grates. Both materials will rust over time but the process is slower with ductile iron.