Grilling Surface for a DIY Barbecue

Almost all of the high heat sprays are not expected to last against direct flame exposure.

I have a outdoor fire pit/BBQ with plain rebar as the grill. Even though it does rust a bit, the exposed rebar is thick enough that it would be decades before I would need to replace it, and the baked on char/oils actually protect the metal quite a bit. The other option would be using stainless steel rods as the grill rack material, then there would be negligible amounts of corrosion.

If i had to remake the grate on my fire pit I would probably use 416 stainless steel rods like these http://amzn.to/2gV2DVD

Also, avoid anything that is chrome or zinc plated. When chrome or zinc gets burnt, they produce toxic byproducts. Just to be safe, I would avoid anything that is plated for your grill grates.

Definitely don't use a non-food treatment for a food contact surface. Those paints will flake off into your food.

How big is the grill going to be? DIY grills in most commercial operations I've seen use unpainted steel road grates. It's a super durable, super low maintenance way to go, but they're heavy as hell and tough to trim to suit your needs if you don't have the equipment.

If you're looking for something a little more refined, restaurant suppliers (like webstaurantstore) sell replacement grates for commercial grills– they're usually cast iron, so you'd have to cover them to keep them from getting rained on. As long as there's a decent layer of cooking grease on them and they're not getting directly rained on, they should resist corrosion. If you see some, sand it down to kill the cancer and oil it.

If you're building it from scratch and can choose the dimensions, consider making it the size of an already popular product, like Weber kettle grills. That way, any grill that works for them will work for you.

Consider using stone. I believe hot stones used to be used for cooking in place of metal pans. I have used a pizza stone for making pizza, bread, chicken, and fries. When the stone is preheated properly the food is very evenly cooked and crisp. Fatty foods like beef may produce a burning smell and you may want to consider using a separate stone for dry foods.

Cleanup is largely just water and/or scraping. No soap or chemicals or oils should ever be used on a stone that I know of.

Finding a large cooking/pizza stone and making a stand to hold one or two in place over the fire is an option.

I would avoid brick or man-made bricks, as they may have undesirable materials in them for human consumption.

Stainless steel, non-magnetic ( eg. 304) would be best. Expensive; However, some grills come with SS racks . Because the SS racks last forever they can be found in junked grills . I recently saw a grill at the curb on our neighborhood "junk" day. Some salvage /recycle yards may sell the SS racks. To clean . build a good fire in your BBQ and heat the racks to dim red heat ( ca. 1100F) , I promise nothing will be living on them. I occasionally do this "self-cleaning" cycle on the SS racks in my gas grill.

Expanded metal grates such as:

are popular improvised grill surfaces. Available at many local hardware stores or online and reasonably priced. You want to avoid galvanized or other coated versions but this material is easy to cut to fit and should serve you well.