Corrosion inhibiting composition and process of using same

Claim 2

A composition for inhibiting mineral scale and corrosion of metal in the presence of water which comprises, parts based on a million parts by weight of water, from about: (a) 0 to 50 parts by weight of an azole, (b) up to 100 parts by weight of citric acid or its alkali metal salts, (c) 0 to 100 parts by weight of a metal molybdate; wherein either the citric acid, alkali metal salt of citric acid or combinations thereof alone or with the molybdate is present in an amount of at least about 3.0 parts per million, and (d) a corrosion inhibiting amount of at least one amino methylene phosphonic acid and the derivatives thereof having the formula: ##STR6## wherein R 1 is a monovalent radical selected from the class consisting of the formulae: ##STR7## wherein R is ##STR8## and y has a value of 1 to 8, x has a value of 1 to 4, and M is a radical selected from the class consisting of hydrogen, an alkali or alkaline earth metal, ammonium, an amino radical and an alkyl or substituted alkyl radical having 1 to 4 carbon atoms.

Claim 3

The composition of claim 1 further characterized in that the amino methylene phosphonic acid and the derivatives thereof are present in an amount ranging from about 2.0 to 50 parts by weight per million parts by weight of water.

Claim 4

The composition of claim 2 further characterized in that citric acid or its alkali metal salt is present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water.

Claim 5

The composition of claim 3 further characterized in that the metal molybdate is present in an amount ranging from 3.0 to 30 parts by weight per million parts by weight of water.

Claim 6

The composition of claim 3 further characterized in that the azole is a triazole present in an amount ranging from about 0.1 to 30 parts by weight per million parts by weight of water.

Claim 7

The composition of claim 3 further characterized in that the phosphonic acid is hexamethylene diamine tetra(methylene phosphonic acid).

Claim 8

The composition of claim 3 further characterized in that the metal molybdate is an alkali metal molybdate and the phosphonic acid is hexamethylene diamine tetra(methylene phosphonic acid).

Claim 9

The composition of claim 3 further characterized in that the phosphonic acid is an amino tri(methylene phosphonic acid).

Claim 10

The composition of claim 3 further characterized in that the phosphonic acid is ethylenediamine tetra(methylene phosphonic acid).

Claim 11

The composition of claim 3 further characterized in that the phosphonic acid is diethylenetriamine penta(methylene phosphonic acid).

Claim 12

The composition of claim 2 further characterized in that the citric acid or its alkali metal salt is present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water, the molybdate is an alkali metal molybdate present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water and the phosphonic acid is hexamethylene diamine tetra(methylene phosphonic acid).

Claim 13

The composition of claim 5 further characterized in that the azole is a triazole present in an amount ranging from about 0.1 to 30 parts by weight per million parts by weight of water and is selected from the class consisting of benzotriazole and tolyltriazole.

Claim 14

The composition of claim 1 further characterized in that the citric acid is present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water and the phosphonic acid is hexamethylene diamine tetra(methylenephosphonic acid).

Claim 15

The composition of claim 3 further characterized in that the composition comprises a dispersing amount of a water-soluble polymeric dispersing agent.

Claim 16

The composition of claim 14 further characterized in that the polymeric dispersing agent is a sulphonated polystyrene.

Claim 17

The composition of claim 11 further characterized in that the composition comprises a dispersing amount of a water-soluble polymeric dispersing agent.

Claim 18

The composition of claim 3 further characterized in that the composition comprises an inhibiting amount of at least one other inorganic corrosion inhibitor selected from the group consisting of nitrates, nitrites, silicates, carbonates and oxides.

Claim 19

A process for inhibiting mineral scale and corrosion of metal in an aqueous system which comprises adding to the water, parts based on a million parts by weight of water, from about: (a) 0 to 50 parts by weight of an azole, (b) up to 100 parts by weight of citric acid or its alkali metal salt, (c) 0 to 100 parts by weight of a metal molybdate; wherein either the citric acid, alkali metal salt of citric acid or combinations thereof alone or with the molybdate is present in an amount of at least about 3.0 parts per million, and (d) a corrosion inhibiting amount of at least one amino methylene phosphonic acid and the derivatives thereof having the formula: ##STR9## wherein R 1 is a monovalent radical selected from the class consisting of the formulae: ##STR10## wherein R is ##STR11## and y has a value of 1 to 8, x has a value of 1 to 4, and M is a radical selected from the class consisting of hydrogen, an alkali or alkaline earth metal, ammonium, an amino radical and an alkyl or substituted alkyl radical of 1 to 4 carbon atoms.

Claim 20

A process for inhibiting mineral scale and corrosion of metal in an aqueous system which comprises adding to the water, parts based on a million parts by weight of water, from about: (a) 0 to 50 parts by weight of an azole, (b) up to 100 parts by weight of citric acid or its alkali metal salt, (c) 0 to 100 parts by weight of a metal molybdate; wherein either the citric acid, alkali metal salt of citric acid or combinations thereof alone or with the molybdate is present in an amount of at least about 3.0 parts per million, and (d) a corrosion inhibiting amount of at least one amino methylene phosphonic acid and the derivatives thereof having the formula: ##STR9## wherein R 1 is a monovalent radical selected from the class consisting of the formulae: ##STR10## wherein R is ##STR11## and y has a value of 1 to 8, x has a value of 1 to 4, and M is a radical selected from the class consisting of hydrogen, an alkali or alkaline earth metal, ammonium, an amino radical and an alkyl or substituted alkyl radical of 1 to 4 carbon atoms.

Claim 21

The process of claim 18 further characterized in that citric acid or its alkali metal salt is present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water, the molybdate is an alkali metal molybdate present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water and the phosphonic acid is hexamethylene diamine tetra (methylene phosphonic acid) present in an amount ranging from about 2.0 to 50 parts per million by weight.

Claim 22

The process of claim 18 further characterized in that the metal molybdate is an alkali metal molybdate present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water and the phosphonic acid is hexamethylene diamine tetra (methylene phosphonic acid).

Claim 23

The process of claim 18 further characterized in that citric acid or its alkali metal salt is present in an amount ranging from about 3.0 to 30 parts by weight per million parts by weight of water and the phosphonic acid is hexamethylene diamine tetra (methylene phosphonic acid).

Claim 24

The process of claim 18 further characterized in that the azole is present in an amount ranging from about 0.1 to 30 parts by weight per million parts by weight of water and is selected from the class consisting of benzotriazole and tolyltriazole.

Claim 25

The process of claim 18 further characterized in that the composition comprises a dispersing amount of a water-soluble polymeric dispersing agent.

Claim 26

The process of claim 23 further characterized in that the polymeric dispersing agent is a sulphonated polystyrene.

Claim 27

The process of claim 18 further characterized in that an effective amount of at least one other inorganic corrosion inhibitor selected from the group consisting of nitrates, nitrites, silicates, carbonates and oxides is added to the water.