Advice on turning a cart into a garden bed

I have had a cart sitting in my shed collecting dust for a couple years and this year I want to turn it into a garden bed to grow spinach and arugula. I have a rough plan on what I want to do but was hoping for some advice/guidance if my plan stinks

I know I need to drill holes for drainage, how many should be enough for a bed this size? Its 8-10 inches deep probably. I was then going to cover the bottom with some kind of liner. I was thinking the kind that is used for hanging garden baskets?

I also don't know if this is even safe. I don't know what kind of metal the cart is made of and don't want anything leeching into the plants or if it will rust when exposed to rain

Any advice would be much appreciated

Thanks!

https://preview.redd.it/xjjye1glc6tg1.jpg?width=3024&format=pjpg&auto=webp&s=e8300a0efa6f222b15f94d65d23d1326910d7bdf

https://preview.redd.it/mc7na1glc6tg1.jpg?width=3024&format=pjpg&auto=webp&s=657f735b45757aede837be0a118775d14b2a749b