Food burns in a pressure cooker when the base loses its layer of moving liquid. Steam keeps the inside of a sealed cooker at around 121 degrees Celsius, but a dry patch on the base has nothing left...
Stainless steel of AISI 304 grade or higher is the safest pressure cooker material for everyday Indian cooking. It doesn't react with acidic food like tamarind, tomato and kokum. Hard anodised alum...