A nonabrasive, corrosion-resistant, hydrophilic coating on aluminum sheet such as fin stock, produced by applying to the sheet surface a coating material containing, in an aqueous vehicle, effective amounts of nitrilotrismethylenetriphosphonic acid, phosphoric acid, and borate material of the group consisting of zinc borate and sodium borate, and essentially free of silica, alumina and precursors thereof, and heating the surface to establish the coating thereon. The coating formulation may also contains up to about 1 wt. % of polyacrylic acid and a surfactant to aid in application.