Cast iron cooking grates are very hard and tough to clean. Somewhat than trying to prevent scratches, the big challenge a bbq grill made from cast iron lies with preventing rust.
When you purchase a new bbq grill, be sure to follow the manufacturer's instructions for how to season your grates. As with cast iron, the first step in keeping your cast iron grates from developing rust is to season it properly before using it.
First time use: Before using a cast iron grate, wash it thoroughly with a mild washing-up liquid to remove the protective wax coating applied for shipping. Rinse with hot water and dry completely with a soft cloth or paper towel. NEVER ALLOW TO RINSE DRY, OR WASH IN A DISHWASHER. Now season the grates to prevent rust and sticking.
Seasoning: A solid vegetable oil is recommended for the initial seasoning. Spread a thin coating of solid vegetable shortening over the entire surface, including all corners, with a paper towel. Do not use salted fats such as butter or margarine. Proceed as follows:
Gas barbecues: Preheat barbecue for 15 minutes; Turn burners to high with lid closed. Allow barbecue to heat grates for 1 to 1 1/2 hours. Turn all burners to OFF, and leave cooking grates in barbecue until they are cool.
Your cast iron cooking grates are now ready to use. To prevent rusting, they should be re-seasoned frequently, particularly when new. If rust occurs, clean with a steel brush. Reapply vegetable shortening and heat as indicated above.