arigram said:
The sink will be built by a friend who has a manufacturing company of metallic professional equipment (for hotels, restaurants, etc) and so it will be metallic.
He doesn't know the exact material to use for photographic chemicals and that's why I ask.
I don't know myself what FRP is or how that would translate to greek terminology.
FRP is fiber glass, used in a lot of things like light-weight car bodies. It comes in liquid or sheets depending on your purpose. It's actually a bit of a pain to deal with it and its toxic fume, but any DIY(do-it-yourself) store has it and sells it relatively inexpensive. Some people prefer epoxy for the same effect, which is odor free.
Commonly some people paint the FRP on the surface of their home-made sinks built with plywood and 2x4". I've made one before. But since you have a professional working for yours with metals, I guess this is not going to suit your purpose. But it's still good to know.
I don't know much about the stainless, but as someone else said, there's a specific number you have to look for.
Meanwhile my current sink is actually a large hard-plastic container/tub (about 4ft wide, 2/3ft deep). I don't know what it's called, but it's a big (green color) instant tub that's used by construction workers for mixing cement and washing tools, etc. It cost me 75 USD, and it's hard as a rock. I drilled a couple of small drain holes on the bottom, attached hoses, and set it in an angle so the water goes to the drain holes. It sits well on my home-made 2x4" frames/legs.
The size of this tub is good for washing prints: two 11x14" trays or one 16x20" tray can fit easily. I use a 6ft work table (also home-made with 2x4"s and a plywood) for the developer, stop and fix trays when I work.
It's not a perfect sink as I want it to be, but it does the job for the most part, and it's as durable and light-weight as a Delta sink in the same size that I had used before. Needless to say, it's chemical-resist and rust-free because it's all plastic. The most advantage is that if I have to replace it the future, I can go knock on the door of any DIY store (or any local contruction supply office) and buy one for sure.
Firecracker
P.S. There's a good book for building a sink called, "BUILD YOUR OWN HOME DARKROOM" by Lista Duren & Will MacDonald. It also shows you how to make other items such as an exhaust fan and a light table.