A heat exchanger tube comprising a primary tubular element for carrying a heating or cooling medium and a secondary heat transfer surface spirally wound about the tubular element. The heat transfer surface is formed in a U-shaped configuration with its base being wound in metal-to-metal contact against the tube surface and the two legs thereof extending radially from the base. Each leg, in turn, is provided with a plurality of slits extending inwardly from the extreme edge thereof to create a dense population of relatively thin spine-like fins radiating from the tube. A meniscus of adhesive is formed between the legs and the surface of the tube which secures the base of the fin strip in metal-to-metal contact against the tube surface and also supports the individual spine-like fins in a radially extended position. In a further embodiment of the invention, the exposed surfaces of the primary and secondary elements are coated with a thin layer of adhesive to protect the tube from corrosion.