Method of increasing corrosion resistance of metals and alloys by treatment with rare earth elements

A method of treating a surface of stainless steels, nickel alloys, copper and copper alloys to increase corrosion resistance by modification of the surface to inhibit cathodic processes, comprising:

• providing an aqueous solution comprising a salt of at least one rare earth element selected from the group consisting of yttrium, gadolinium, cerium, europium, terbium, samarium, neodymium, praseodymium, lanthanum, holmium, ytterbium, dysprosium, erbium, and combinations thereof, but substantially exclusive of halides, and a pH-modifying agent present in an amount effective to adjust the pH to from about 0.5 to an upper solubility limit of said salt of at least one rare earth element in said aqueous solution as a function of pH;
• and
• exposing said surface to the aqueous solution in a single step exposure for an effective period of time with the solution being at an effective temperature to modify said surface to inhibit cathodic processes.

A method of treating a surface of aluminum and alloys thereof to increase corrosion resistance by modification of the surface to inhibit cathodic processes, comprising;

• providing an aqueous solution comprising a salt of at least one rare earth element selected from the group consisting of yttrium, gadolinium, cerium, europium, terbium, samarium, neodymium, praseodymium, lanthanum, holmium, ytterbium, dysprosium, erbium, and combinations thereof, but substantially exclusive of halides, said at least one rare earth being present in an amount of from about 2% by weight to saturation, the aqueous solution including a surfactant and a pH-modifying agent present in an amount effective to adjust the pH to from about 4.5 to an upper solubility limit of said salt of at least one rare earth element in said aqueous solution as a function of pH;
• and
• exposing a surface of said aluminum or alloy thereof to the aqueous solution, in a single step treatment, for an effective period of time and with the solution being at an effective temperature to modify said surface to inhibit cathodic processes but not to purposefully grow a thick protective oxide coating thereon.