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In an acidic aqueous coating solution which contains zirconium, hafnium or titanium, and fluoride and which is effective in forming on an aluminum surface a non-chromate coating to which overlying coatings adhere tightly and which is corrosion resistant and resists being discolored when subjected to

In an acidic aqueous coating solution which contains zirconium, hafnium or titanium, and fluoride and which is effective in forming on an aluminum surface a non-chromate coating to which overlying coatings adhere tightly and which is corrosion resistant and resists being discolored when subjected to hot water, the improvement comprising including in said coating solution a combination of surfactants in an amount such that a coating formed from the surfactant-containing coating solution has an improved tendency to resist being discolored by hot water.

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An acidic aqueous coating solution which is effective in forming a non-resinous, non-chromate, corrosion-resistant coating on an aluminum surface, said solution consisting essentially of (a) a metal containing substance wherein the metal is selected from the group consisting of zirconium, titanium,

An acidic aqueous coating solution which is effective in forming a non-resinous, non-chromate, corrosion-resistant coating on an aluminum surface, said solution consisting essentially of (a) a metal containing substance wherein the metal is selected from the group consisting of zirconium, titanium, and hafnium ions, and mixtures of two or more of said substances, said metal being present in the solution in an amount of at least about 0.5×10-3 m/l, (b) fluoride in an amount at least sufficient to combine with all of said metal, and (c) at least two surfactants present in amounts such that the coating formed from said solution has an improved tendency to resist being discolored by hot water, and wherein when two surfactants are present they are present in a weight ratio of from about 0.3:1 to about 3:1.