Many of grates are porcelain enamelled. The porcelain enamel makes them easy to clean and maintain, but there are some things you may want to consider doing in order to make sure they last as long as possible.

Avoid scraping the grates
If you scrape your grates with metal tools like your spatula you could damage the porcelain enamel. 

Brush the grates
The easiest and best way to make sure your grates last as long as possible is to brush them every time you use the grill. Just preheat the grill on high for 15 minutes with the lid closed and then brush the grates clean with a Weber Stainless Steel Grill Brush.

No soaps with citrus
Washing grates in a sink usually isn't necessary, but if you find yourself with a reason to do so try to avoid using any soaps with citrus cleaning agents in them. They can promote corrosion. You can soak the grates in hot water to remove stubborn particles and then use a mild dishwashing liquid and nylon/soft abrasive pads or brushes. Make sure you use a soft cloth or paper towel to thoroughly dry the grates when you’re done. Letting them air-dry can also promote corrosion.