Fridge Water Evaporator.
The water from the fridge interior fins drip into a tray. This water is fed back to the evaporator container. This container is secured over the Coolant circulator pipe. This in turn operates quite hot, causing the container to get warm and boiling off the water in the container. This could be the reason for the gas assembly rusting!
Note the gas assembly burner, before it was changed.
The Gas Burner Flue jacket is low down, and on my fridge caused the viewing glass inside the fridge to obscure the flame. I have since cut a piece out of the jacket, opposite the fridge viewing glass. About the size of a 2pence piece. The difference is amazing with it now showing the flame for easy viewing.