Materials and coatings for BBQ grills and smokers

I am a young mechanical engineer working in an unrelated industry, wondering if someone with experience in the matter can help.

I have been wanting to construct a 55 gallon steel drum smoker as well as a mangal (grill) for my personal use (and home fabrication practice). In my research for what type of drum I should use and how I should strip it’s coating to make it safe for use, I found many guides and forum posts with rather contradicting information. I’m further away from an answer than when I started my research, but it got me asking myself:

What materials, coatings, and processes are used by industry to make commercially available grills you buy at retail outlets?

Are there specific grades of steel or stainless steel that industry has defaulted to? I have heard that stainless and alloy steels 'can’ leach chromium and heavy metals into your food, but no more detail than that. Or are ‘hot’ parts just plain sheet steel with a high temperature coating?

In my home country I saw mangals made from road signs, and I’d like to avoid that design philosophy :joy: