Passivating metal surfaces

Claim 1

A method for the simultaneous neutralization and passivation of an acid-treated ferrous metal surface comprising: contacting an acid-treated ferrous metal surface with an aqueous solution consisting essentially of a. a base selected from alkali metal hydroxides, ethanolamines, alkali metal carbonates, alkali metal gluconates, alkali metal borates and mixtures thereof, said base being present in said aqueous solution in the range of from about 0.01 to about 3.0 percent base by weight of said solution; b. an oxygen containing gas present in said solution in an amount sufficient to saturate said solution with oxygen at the temperature and pressure of said contacting; c. hydrazine present in said solution in the range of from about 0.001 to about 0.1 percent hydrazine by weight of said solution; and d. an iron complexing agent selected from the group consisting of alkali metal gluconates; alkali metal salts of ethylenediaminetetraacetic acid; ethanolamines; polyphosphonic acids having the formula ##STR3## wherein R 1 is selected from the class consisting of C 1 to C 12 alkyl groups and the group ##STR4## where R 2 is selected from the class consisting of --H,--PO 3 H 2 , C 1 to C 12 alkyl groups, and the group ##STR5## the alkali metal and amine salts of said polyphosphonic acids; and mixtures thereof; said complexing agent being present in said aqueous solution in the range of from about 0.01 to about 1.0 percent complexing agent by weight of said solution; maintaining said contact for a time sufficient to neutralize and passivate said ferrous metal surface, wherein the pH of said solution is greater than about 8.0 and said contacting is conducted at a temperature greater than about 220° F and less than the degradation temperature of chemicals in said solution.

Claim 2

A method for the simultaneous neutralization and passivation of an acid-treated ferrous metal surface comprising: contacting an acid-treated ferrous metal surface with an aqueous solution consisting essentially of a. a base selected from alkali metal hydroxides, ethanolamines, alkali metal carbonates, alkali metal gluconates, alkali metal borates and mixtures thereof, said base being present in said aqueous solution in the range of from about 0.01 to about 3.0 percent base by weight of said solution; b. an oxygen containing gas present in said solution in an amount sufficient to saturate said solution with oxygen at the temperature and pressure of said contacting; c. hydrazine present in said solution in the range of from about 0.001 to about 0.1 percent hydrazine by weight of said solution; and d. an iron complexing agent selected from the group consisting of alkali metal gluconates; alkali metal salts of ethylenediaminetetraacetic acid; ethanolamines; polyphosphonic acids having the formula ##STR3## wherein R 1 is selected from the class consisting of C 1 to C 12 alkyl groups and the group ##STR4## where R 2 is selected from the class consisting of --H,--PO 3 H 2 , C 1 to C 12 alkyl groups, and the group ##STR5## the alkali metal and amine salts of said polyphosphonic acids; and mixtures thereof; said complexing agent being present in said aqueous solution in the range of from about 0.01 to about 1.0 percent complexing agent by weight of said solution; maintaining said contact for a time sufficient to neutralize and passivate said ferrous metal surface, wherein the pH of said solution is greater than about 8.0 and said contacting is conducted at a temperature greater than about 220° F and less than the degradation temperature of chemicals in said solution.

Claim 9

A method for the simultaneous neutralization and passivation of acid-treated ferrous metal surfaces, comprising: contacting an acid-treated ferrous metal surface with an aqueous solution containing a base, an oxygen containing gas and an iron complexing agent; maintaining said contact for a time sufficient to neutralize and passivate said ferrous metal surface, wherein the pH of said solution is greater than about 8.0 and said contacting is conducted at a temperature greater than about 220° F and less than the degradation temperature of chemicals in said solution; wherein said base is a mixture of sodium hydroxide and sodium carbonate, said iron complexing agent is 1-hydroxyethylidine-1,1-diphosphonic acid, and said base is present in said solution in the range of from about 0.01 to about 1.0 percent complexing agent by weight of said solution; and wherein said oxygen containing gas is present in said solution in an amount sufficient to saturate said solution with oxygen at the temperature and pressure of said contacting.

Claim 10

A method for the simultaneous neutralization and passivation of acid-treated ferrous metal surfaces, comprising: contacting an acid-treated ferrous metal surface with an aqueous solution containing a base, an oxygen containing gas and an iron complexing agent; maintaining said contact for a time sufficient to neutralize and passivate said ferrous metal surface, wherein the pH of said solution is greater than about 8.0 and said contacting is conducted at a temperature greater than about 220° F and less than the degradation temperature of chemicals in said solution; wherein said base is a mixture of sodium hydroxide and sodium carbonate, said iron complexing agent is 1-hydroxyethylidine-1,1-diphosphonic acid, and said base is present in said solution in the range of from about 0.01 to about 1.0 percent complexing agent by weight of said solution; and wherein said oxygen containing gas is present in said solution in an amount sufficient to saturate said solution with oxygen at the temperature and pressure of said contacting.