By 'seasoning' it. You slather it with some type of cooking oil and that protects it from turning bright orange with rust.
Cast iron is the material of choice as it is cheaper than surgery grade stainless steel, it retains the heat and it is a traditional material that people expect.
As for where you can buy yourself a grill made from cast iron, the options are many. In towns there are shops that sell such things. You can walk into such a shop, exchange money and get your own BBQ grill in genuine cast iron.
Pretty much all Weber (a very, very mainstream grill brand available the world over) grills/“grates” are cast iron. It works fine! You do typically have to replace them every three to five years, but this isn’t that big a deal, the replacement grates are stocked at most home improvement stores.
> Pretty much all Weber (a very, very mainstream grill brand available the world over) grills/“grates” are cast iron.
No, they are “plated steel” for the cooking grate, and “heavy gauge steel” for the charcoal grate; at least per the specs on their website. (Which matches every Weber I've used over several decades.)
While I believe they receive some kind of coating, Weber themselves refer frequently to them being cast iron.
From their site, “how to care for your cast iron cooking grates”. Quoting Weber’s website, “All our 2017 gas grills except for the Summit and Genesis II LX come with porcelain enameled cast iron cooking grates.”. The spec sheet on the site for virtually every gas grill lists a cast iron grate.
Oh, Weber gas grills. When you said all Weber grills, I thought of and only checked their charcoal grills, the round charcoal grill being their iconic product.
