Iron Trench Grates

Cast iron trench drain grates are made by melting metal into a liquid form then pouring this liquid metal into a cavity shaped like the finished part.  The cavity is shaped from a sticky sand.  After the cast iron is poured into the cavity, it is allowed to cool.  Once the iron grate has cooled the sand is broken and cleaned off of the cast iron leaving a trench drain grate.

During the melting and casting process the metallurgy can be altered by changing raw components and additives.  Iron trench drain grates are categorized into two broad categories; Ductile iron and Cast iron.  Cast iron is often called "pig iron".  This is the oldest technology and produces a strong iron part.  Additives have become more popular in past years that create a spherical grain structure in the iron imparting ductility.  These metals are called "Ductile Iron".  The ductility means that they can take more loading without cracking or breaking.  Ductile iron grates are typically used when heavy loading such as Aircraft might be present.

Iron grates can be cast in a variety of grades and each class of iron has several grades.  Generally these are unimportant to the designer as long as the iron grate can reach the required loading.  Cast iron is governed by AASHTO M105 class 35B or ASTM A48 Class 35B.  Ductile irons are governed by ASTM A536.

Cast iron grates and ductile iron grates can be used in their natural state or they can be coated.  Iron trench grates posses a natural corrosion resistance that is inherent to their material.  When exposed to nature iron forms a protective surface coating of iron oxide which slows the corrosion.  The early stages of this iron oxide is a reddish brown but with time ductile and cast iron trench grates will age to a dark brown similar to any other manhole casting.

Ductile iron and cast iron grates can also be coated with a protective finish.  Iron trench grates are often coated with epoxy paint, powder coated, oil baked, or hot dip galvanized.  For exterior applications, coating an iron trench drain grate is usually a waste of money.  With no coating an iron grate will outlast the pavement in most cases.  It should also be noted that in some cases the DOT (department of transportation) specifications may not allow iron trench grates to be painted or coated.


For interior trench drains a cast or ductile iron grate is usually coated.  This is mostly for aesthetics, however, ASME A112-6-3 does require iron trench drain grates to be coated with "a suitable paint, lacquer, or synthetic coating of quality to provided protection against rusting of ferrous surfaces during normal handling and warehousing prior to installation."  Most of the Dura Trench grates come standard with a black e-coating.  We can powder coat grates to any color upon request.

Cast iron grates and Ductile iron grates come in all sorts of patterns and load ratings.  They are a good mix of quality and cost making iron grates the most widely used trench drain grate.  Dura Trench can also cast custom patterns for customers.  We can cast unique ornamental slots, logos, or any other detailed and unique feature.  We cast a lot of radius trench drain grates for special applications.

Cast and ductile iron grates are utilized in almost every application.  Some common applications are airports, sea ports, industry, roadways, parking lots, fountains, gas stations, utility trenches, fire stations, loading docks, parks, etc.  

6" cast iron radius trench drain grates
48" iron covers for utility trench
Cast iron trench drain grates in roadway