Finish and Material Options

Materials: All IRONSMITH cast products are available in:

1.Cast gray iron ASTM A48 class 30 minimum from 100% locally recycled post consumer materials, Mostly automobile parts

2. Recycled aluminum. Mixed alloys both post consumer and post industrial mostly from automobile rims.

3. Bronze/brass alloys*. Standard material used is alloy C854 yellow brass for castings and C385 Architectural bronze for frame angles. Yellow brass contains approx. 67% Copper, 29% Zinc, 3% Lead, and 1% Tin. Architectural Bronze contains approx. 55 -60% copper,40% zinc, 2 - 3.8% lead . Due to their lead content C854 and C385 alloys may not be suitable for systems to provide water for human consumption. IRONSMITH copper alloy products are not ANSI/NSF 61 tested. Please check your local codes.

Click here for a brief discussion on Bronze / brass

4. Special alloys of aluminum, bronze and brass available by special request.

Finishes: Natural unfinished gray iron will develop an attractive rust patina that does not penetrate or weaken the casting and is maintenance free. Natural aluminum will age to a pewter gray. Our standard brushed surface stays bright for years.

Standard surface finishes:
gray iron as cast (fine pebbly texture)
Aluminum and copper alloys 50 grit brushed random orbit pattern
Aluminum and copper alloys can be special ordered with finer brushed finishes up to 120 grit or sandblasted.

Please call for samples

Alternately, the following finishes can be provided to fit your needs and budget.

1. Primed for your choice of top coat;
2. Primed and painted in exterior enamel or primed and painted exterior polyurethane;
3. Powder coated;
4. Zinc undercoating.

5. Tree grate frames can be provided Hot dip galvanized.

We can match paint finishes to your color choice and a range of colors are available in powder coat. Please call with your requirement.

We use Sherwin Williams Industrial paints for enamel or polyurethane finishes.

We can powder coat to the standard range of RAL colors. We also suggest Cardinal Industrial Finishes powder coats. Be sure when selecting a powder coat color that it is available in a polyester base for good weatherability. Epoxies should not be used for exterior applications. Cardinal has color charts viewable on line. We recommend requesting a color chart for reference.(click on highlighted names to link to their sites)

Cast iron is extremely susceptible to rust. Some rust should be expected however good the paint system. For this reason the following guidelines should be used when specifying finishes for cast products.

1. Use only dark colors; black, dark brown, dark green, dark gray, etc.
2. If light colors are required, specify a zinc undercoat to help reduce rust bleed through.
3. When no rust can be tolerated, specify cast aluminum.


Unfinished casting surfaces exceed A.D.A coefficient of friction requirements.

High gloss powder coats should be avoided for walking surfaces as they may be slippery when wet. We use a low gloss textured black powder as our standard black finish.

SHARKGRIP ® may be added to enamel or polyurethane paint to improve slip resistance.

Unfinished grates that have rusted to bright reddish orange on site can be instantly darkened to a rich chocolate brown by applying a product called Black Max™. This is for product already installed on site and is listed here merely for reference,

Read our statement on Baked Oil Finish for Cast Iron

Unfinished cast metals weather well in most instances. Cast iron, aluminum, and bronze will last many decades with little change if left unfinished. The natural changes in metals due to atmospheric exposure is called patination. A metals patina is actually a thin layer of oxides of the metal, the products of corrosion, that acts to slow down further corrosion.

On cast iron the patina is iron oxide ( to the chemist it's iron oxide to the rest of us it's just rust). Cast iron rusts extremely quickly. In fact cast iron will begin to rust when the relative humidity exceeds about 64%! Unlike steel, however, the rust on cast iron is not invasive but will act like a coating to prevent deep rusting. Therefore rusting on cast iron gratings in no way harms their structural integrity. The patination of cast iron grates goes through a predictable set of stages. The duration of each stage depends on local moisture conditions and the amount of foot traffic. So grates will progress slower in the desert than at the beach but the process is inevitable regardless of location.


newly cast iron grate
grates usually arrive on site like this.

Iron grate about three weeks after installation near the ocean. Iron grate after about three years in Phoenix Arizona. Unfinished iron grate after about one year at a California theme park. Grates are hosed down daily.
Natural Aluminum grates get a coating of aluminum oxide. which is very hard. This thin transparent patina keeps aluminum grates looking bright for years. The photo at right shows an unfinished aluminum grate after three years near the ocean in Florida.
Bronze / brass: copper alloys are well known for their patinas. The natural patination of bronze is unpredictable and is part of its charm. Colors arising from the oxidation of our standard copper alloys range from pale greens and yellows to white to turquoise. Most very dark bronze patinas are produced artificially by a chemical process.  

Samples of unfinished grates