Barbecue grills are subject to extremely high temperatures for long periods of time, which can eventually cause the interior and exterior paint to peel. If you're thinking about re-painting the inside of your grill, the best advice is: don't. Using a traditional, liquid-based paint on the inside of a barbecue grill is pointless, as the paint will eventually chip and imbue your food with toxic chemicals as it degrades. However, the automotive aftermarket offers a perfect coating solution that will help to ensure that your fire-pit remains safe and beautiful for more than a century to come.
Disassemble the entire grill if portable, or remove the fire-pit from the base if you're servicing a built-in grill. Remove the legs, grill racks and all hardware from the grill, and disassemble sub-assemblies like handles and knobs to separate the metal components.
Hose the grill out to remove any built-up charcoal. Don your safety gear. If you don't have a leather apron, wear a heavy leather coat and zip it up. These steps are crucial, because your grinder's wire wheel will periodically shed wire bristles as you use it. These wires are needle-sharp and will shoot out at very high speeds, lodging in any exposed flesh unfortunate enough to be in the way.
Remove any existing paint from the inside and outside of the portable grill, or wire-brush the inside of your removable fire pit. Continue wire-brushing until you get down to the bare metal. You can also use a more aggressive medium-grade, steel-bristle wire brush but be very careful not to damage delicate components.
Wipe the entire assembly down with paint thinner on a rag to remove as much of the metal dust as possible. Allow the paint thinner to evaporate away and immediately slide the component into a garbage bag or wrap it with plastic wrap. Duct tape the bag closed.
Repeat the wire-brushing procedure on every component you'd like to resurface. Place them all into sealed bags. Wire brush all of the bolt threads and bolt heads, and spray the bolt heads with two light coats of grill paint.
Take your bagged parts or fire pit to your local powder-coating shop, and have them spray everything with the type of ceramic-metallic powder-coating designed for exhaust headers. This powder-coating will resist temperatures of well over 1,500 degrees, and comes in a variety of finishes. The standard ceramic coat is designed for piston tops and combustion chambers, and is tan in color. You'll probably want to use the chrome-finish powder-coat, as it will be just as durable in this application, is easier to clean than satin finishes and will remain shiny and beautiful for many years to come.
Reassemble the grill or reinstall the fire pit. These ceramic coatings are actually thermal insulators, and the chrome-finish coating is a thermal reflector. This means that your grill will not only look better, but will contain the heat inside to cook faster and remain cooler to the touch on the outside.