Kevin: It looks to be galvanized steel to me. Probably even thicker than 18 gauge. It will last a long time. Not sure how long though. Not as long as stainless. It will probably take years to get a full assessment of how it works out for you. LOL.
Just a word of caution. If those plates are galvanized, it could pose a health risk. Heating them to temps you typically find inside of a BBQ grill will cause it to release toxic fumes.
Cooking With Galvanized Steel. Heating a galvanized metal surface releases zinc fumes. These fumes accumulate in the food but are also toxic to breathe. For this reason, utensils with galvanized surfaces should not be used in food cooking.
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