Aluminium and aluminium alloy having corrosion-resistant protective layer, and methods of making such a layer

Claim 1

A body made of metal selected from aluminum and aluminum alloy having a corrosion-resistant bright dense protective layer at a surface thereof, which layer has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, and having a reflectance of at least 80%.

Claim 19

A method of providing corrosion-resistance to a body which is to be exposed to a water-containing environment, said body being made of a metal selected from aluminum and aluminum alloy, comprising the step of providing on a surface of said body a corrosion-resistant bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene, by subjecting a surface of said body to an oxidative electrolytic treatment in an aqueous solution for forming said protective layer and having a pH in the range 2 to 7.

Claim 20

A method of providing corrosion-resistance to a body which is to be exposed to a water-containing environment, said body being made of a metal selected from aluminum and aluminum alloy, comprising the step of providing on a surface of said body a corrosion-resistant bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene, by subjecting a surface of said body to an oxidative electrolytic treatment in an aqueous solution for forming said protective layer and having a pH in the range 2 to 7.

Claim 21

A method of providing a corrosion-resistant layer on a body made of a metal selected from aluminum and aluminum alloy, comprising the step of subjecting a surface of said body to an oxidative electrolytic treatment in an aqueous solution having a pH in the range 2 to 7, containing at least one anion selected from the group comprising sulphate, phosphate and condensed phosphates but from which borate ions are essentially absent, and further containing at least one organic chelating agent capable of complexing aluminum, so as to form on said surface said corrosion-resistant layer in the form of a bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene.

Claim 22

A method of providing a corrosion-resistant layer on a body made of a metal selected from aluminum and aluminum alloy, comprising the step of subjecting a surface of said body to an oxidative electrolytic treatment in an aqueous solution having a pH in the range 2 to 7, containing at least one anion selected from the group comprising sulphate, phosphate and condensed phosphates but from which borate ions are essentially absent, and further containing at least one organic chelating agent capable of complexing aluminum, so as to form on said surface said corrosion-resistant layer in the form of a bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene.

Claim 28

A method of providing a corrosion-resistant layer on a body made of a metal selected from aluminum and aluminum alloy, comprising the steps of (a) contacting a surface of said body with an aqueous solution having a pH in the range 2 to 7 of an organic chelating agent capable of complexing aluminum, and (b) after step (a), subjecting said surface to an oxidative electrolytic treatment in an aqueous solution having a pH in the range of 2 to 7, containing at least one anion selected from the group comprising sulphate, phosphate and condensed phosphates but from which borate ions are essentially absent, said steps (a) and (b) in combination being carried out so as to form on said surface said corrosion-resistant layer in the form of a bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound, selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene.

Claim 29

A method of providing a corrosion-resistant layer on a body made of a metal selected from aluminum and aluminum alloy, comprising the steps of (a) contacting a surface of said body with an aqueous solution having a pH in the range 2 to 7 of an organic chelating agent capable of complexing aluminum, and (b) after step (a), subjecting said surface to an oxidative electrolytic treatment in an aqueous solution having a pH in the range of 2 to 7, containing at least one anion selected from the group comprising sulphate, phosphate and condensed phosphates but from which borate ions are essentially absent, said steps (a) and (b) in combination being carried out so as to form on said surface said corrosion-resistant layer in the form of a bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound, selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene.

Claim 33

A method of providing a corrosion-resistant layer on a body made of a metal selected from aluminum and aluminum alloy, comprising the step of non-electrolytically contacting a surface of said body with an aqueous solution having a pH in the range 2 to 7 of an organic chelating agent capable of chelating aluminum to form an insoluble chelated aluminum compound, which compound has a stability constant of at least 5, so as to form on said surface said corrosion-resistant layer in the form of a bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene.

Claim 34

A method of providing a corrosion-resistant layer on a body made of a metal selected from aluminum and aluminum alloy, comprising the step of non-electrolytically contacting a surface of said body with an aqueous solution having a pH in the range 2 to 7 of an organic chelating agent capable of chelating aluminum to form an insoluble chelated aluminum compound, which compound has a stability constant of at least 5, so as to form on said surface said corrosion-resistant layer in the form of a bright dense protective layer which has a thickness in the range 50 to 500 nm and comprises aluminum oxide and a chelate complex of aluminum and at least one organic chelating compound selected from the group consisting of 8-hydroxyquinoline, derivatives of 8-hydroxyquinoline and N-nitrosophenyl-hydroxylamineammonium, aminophenols, carboxylic acids and their salts, alizarin, derivatives of alizarin, ethylenediamine tetraacetic acid, sulpho-salicyclic acid, α-amino acids, β-diketones, and chelating agents based on naphthalene.