The cooking grids is one of the most important parts of a gas grill, it's where you place the food! Quality cooking grids should be durable and help keep food from sticking. It doesn't need to be a nonstick material, but it should prevent food from sticking excessively. Grids are made from a variety of materials, but the most popular types are stainless steel rod, cast iron, and porcelain coated steel.
Stainless Steel Rod
Excellent quality, unlikely to rust. These come in varying thicknesses, and the thicker it is the better. Stainless lasts for a long time and it requires the least amount of maintenance.
Cast iron is heavy and but offers good heat retention and great grill marks. Some brands use a porcelain coating over the cast iron for more protection against rust, but others leave them unprotected. If they don't have a protective coating, cast iron grates need to be well taken care of so they last. It's important to keep the grate clean and oiled to prevent rusting.
Porcelain Coated Steel
Low quality, non-stick cooking grid. The disadvantage with porcelain is when the paint chips off, the bare metal underneath is exposed where it can quickly rust. If you have porcelain coated grates, you need to keep hard metal scrapers and tools away from it. You can use brushes with metal bristles, but scrapers can possibly chip the coating.
Specialty Cooking Grids
Most brands have cooking grids that we mentioned above, but a few have “specialty” cooking grids. Here's a little more about them:
Cast Stainless Steel
Arguably one of the best cooking grids available. Instead of welding, this type of cooking grid is cast from a mold, so it's completely solid. It's 304 grade stainless, which gives it the best protection against rust. The style of grate pictured here is also reversible, and each side can accommodate different foods. One side is ideal for searing steaks and burgers, while the other is perfect for veggies and fish.
Aluminum - Unique and reversible design, will not rust.
Expanded Stainless - Thin material but better at keeping food from falling through.
Chrome Rod - Lowest quality, most likely to rust. Once the chrome coating wears off, the bare steel underneath can rust quickly.