Control of iron induced fouling in water systems

Claim 1

A method of inhibiting corrosion and controlling deposition in an aqueous medium contained in a cooling water system of the type comprising iron species present in said medium in a deposit forming amount and under deposit forming conditions, said iron species being admitted into said medium from a well-water makeup source, said method being capable of providing for the formation of a protective passive oxide film on metallic surfaces in contact with said aqueous medium, said medium being further characterized by the absence of an organo-phosphonic acid compound therein, wherein said method consists essentially of: (i) assuring that the pH of said aqueous medium is 5.5 or above; (ii) assuring that the aqueous medium contains a calcium or other appropriate ion concentration selected from the group consisting of zinc, nickel and chromium and mixtures thereof; and (iii) adding to said aqueous medium (a) a water-soluble polymer comprising moieties derived from an acrylic acid or water-soluble salt thereof and moieties of an hydroxylated lower alkyl acrylate, wherein the moieties of the polymer have the following formulas: ##STR1## wherein R is hydrogen or a lower alkyl of from 1 to 3 carbon atoms; R 1 is OH, OM or NH 2 where M is a water-soluble cation; R 2 is a lower alkyl of from about 2 to 6 carbon atoms and the mole ratio of x:y is 34:1 to 1:4; and (b) a water-soluble orthophosphate compound; said polymer, together with the orthophosphate compound, being effective to promote the formation of said metal oxide film with no attendant deposition of said iron, and the amount of (a) and (b) being added being sufficient to provide a substantially scale-free protective passive oxide film on the metallic surface.

Claim 2

A method of inhibiting corrosion and controlling deposition in an aqueous medium contained in a cooling water system of the type comprising iron species present in said medium in a deposit forming amount and under deposit forming conditions, said iron species being admitted into said medium from a well-water makeup source, said method being capable of providing for the formation of a protective passive oxide film on metallic surfaces in contact with said aqueous medium, said medium being further characterized by the absence of an organo-phosphonic acid compound therein, wherein said method consists essentially of: (i) assuring that the pH of said aqueous medium is 5.5 or above; (ii) assuring that the aqueous medium contains a calcium or other appropriate ion concentration selected from the group consisting of zinc, nickel and chromium and mixtures thereof; and (iii) adding to said aqueous medium (a) a water-soluble polymer comprising moieties derived from an acrylic acid or water-soluble salt thereof and moieties of an hydroxylated lower alkyl acrylate, wherein the moieties of the polymer have the following formulas: ##STR1## wherein R is hydrogen or a lower alkyl of from 1 to 3 carbon atoms; R 1 is OH, OM or NH 2 where M is a water-soluble cation; R 2 is a lower alkyl of from about 2 to 6 carbon atoms and the mole ratio of x:y is 34:1 to 1:4; and (b) a water-soluble orthophosphate compound; said polymer, together with the orthophosphate compound, being effective to promote the formation of said metal oxide film with no attendant deposition of said iron, and the amount of (a) and (b) being added being sufficient to provide a substantially scale-free protective passive oxide film on the metallic surface.

Claim 7

A method of inhibiting corrosion and controlling deposition in an aqueous medium contained in a cooling water system of the type comprising iron species present in said medium in a deposit forming amount and under deposit forming conditions, said iron species being admitted into said medium from a wall-water makeup source, said method being capable of providing for the formation of a protective passive oxide film on metallic surfaces in contact with said aqueous medium, said medium being further characterized by the absence of an organo-phosphonic acid compound therein, wherein said method consists essentially of: (i) assuring that the pH of said aqueous medium is 5.5 or above; (ii) assuring that the aqueous medium contains a calcium or other appropriate ion concentration selected from the group consisting of zinc, nickel and chromium and mixtures thereof; and (iii) adding to said aqueous medium (a) a water-soluble polymer comprising moieties derived from an acrylic acid or water-soluble salt thereof and moieties of an hydroxylated lower alkyl acrylate, wherein the moieties of the polymer have the following formulas: ##STR2## wherein R is hydrogen or a lower alkyl of from 1 to 3 carbon atoms; R 1 is OH, OM or NH 2 where M is a water-soluble cation; R 2 is a lower alkyl of from about 2 to 6 carbon atoms and the mole ratio of x:y is 34:1 to 1:4; and (b) a water-soluble orthophosphate compound; and (c) a water-soluble polyphosphate compound; said polymer, together with the orthophosphate compound being effective to promote the formation of said metal oxide film with no attendant deposition of said iron, and the amount of (a), (b) and (c) being added being sufficient to provide a substantially scale-free protective passive oxide film on the metallic surface.

Claim 8

A method of inhibiting corrosion and controlling deposition in an aqueous medium contained in a cooling water system of the type comprising iron species present in said medium in a deposit forming amount and under deposit forming conditions, said iron species being admitted into said medium from a wall-water makeup source, said method being capable of providing for the formation of a protective passive oxide film on metallic surfaces in contact with said aqueous medium, said medium being further characterized by the absence of an organo-phosphonic acid compound therein, wherein said method consists essentially of: (i) assuring that the pH of said aqueous medium is 5.5 or above; (ii) assuring that the aqueous medium contains a calcium or other appropriate ion concentration selected from the group consisting of zinc, nickel and chromium and mixtures thereof; and (iii) adding to said aqueous medium (a) a water-soluble polymer comprising moieties derived from an acrylic acid or water-soluble salt thereof and moieties of an hydroxylated lower alkyl acrylate, wherein the moieties of the polymer have the following formulas: ##STR2## wherein R is hydrogen or a lower alkyl of from 1 to 3 carbon atoms; R 1 is OH, OM or NH 2 where M is a water-soluble cation; R 2 is a lower alkyl of from about 2 to 6 carbon atoms and the mole ratio of x:y is 34:1 to 1:4; and (b) a water-soluble orthophosphate compound; and (c) a water-soluble polyphosphate compound; said polymer, together with the orthophosphate compound being effective to promote the formation of said metal oxide film with no attendant deposition of said iron, and the amount of (a), (b) and (c) being added being sufficient to provide a substantially scale-free protective passive oxide film on the metallic surface.