The invention pertains to a flat product in the form of a wall for a heat exchanger that is operated with cooling mediums in the form of corrosive liquids that contain biological organisms. In order to protect the wall of the heat exchanger against corrosion on the side that comes in contact with the cooling medium and to prevent biological organisms from settling down on the heat exchanger wall, the wall consists of a titanium or titanium alloy layer and a copper/titanium alloy layer that is integrally connected to the titanium or titanium alloy layer by means of an intermediate alloy layer.