EP1489199A1 - Corrosion resistant coating composition and process and coated magnesium - Google Patents
Corrosion resistant coating composition and process and coated magnesium Download PDFInfo
- Publication number
- EP1489199A1 EP1489199A1 EP04253681A EP04253681A EP1489199A1 EP 1489199 A1 EP1489199 A1 EP 1489199A1 EP 04253681 A EP04253681 A EP 04253681A EP 04253681 A EP04253681 A EP 04253681A EP 1489199 A1 EP1489199 A1 EP 1489199A1
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- EP
- European Patent Office
- Prior art keywords
- magnesium
- solution
- phosphonic acids
- corrosion
- phosphate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 238000005260 corrosion Methods 0.000 title claims abstract description 30
- 230000007797 corrosion Effects 0.000 title claims abstract description 30
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 239000011777 magnesium Substances 0.000 title claims abstract description 14
- 229910052749 magnesium Inorganic materials 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 title claims description 4
- 230000008569 process Effects 0.000 title claims description 4
- 239000008199 coating composition Substances 0.000 title 1
- 229910000861 Mg alloy Inorganic materials 0.000 claims abstract description 16
- 239000003112 inhibitor Substances 0.000 claims abstract description 13
- 239000000758 substrate Substances 0.000 claims abstract description 10
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims abstract description 6
- ABLZXFCXXLZCGV-UHFFFAOYSA-N phosphonic acid group Chemical group P(O)(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 claims abstract description 4
- 150000003839 salts Chemical class 0.000 claims abstract description 4
- -1 fluoride ions Chemical class 0.000 claims description 27
- 238000000576 coating method Methods 0.000 claims description 14
- 239000011248 coating agent Substances 0.000 claims description 13
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 9
- YDONNITUKPKTIG-UHFFFAOYSA-N [Nitrilotris(methylene)]trisphosphonic acid Chemical compound OP(O)(=O)CN(CP(O)(O)=O)CP(O)(O)=O YDONNITUKPKTIG-UHFFFAOYSA-N 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 8
- 229910019142 PO4 Inorganic materials 0.000 claims description 6
- 150000007513 acids Chemical class 0.000 claims description 6
- 239000010452 phosphate Substances 0.000 claims description 6
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000007739 conversion coating Methods 0.000 abstract description 13
- FQKMRXHEIPOETF-UHFFFAOYSA-N F.OP(O)(O)=O Chemical compound F.OP(O)(O)=O FQKMRXHEIPOETF-UHFFFAOYSA-N 0.000 abstract description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 3
- 150000002222 fluorine compounds Chemical class 0.000 description 3
- GNSKLFRGEWLPPA-UHFFFAOYSA-M potassium dihydrogen phosphate Chemical compound [K+].OP(O)([O-])=O GNSKLFRGEWLPPA-UHFFFAOYSA-M 0.000 description 3
- BFXAWOHHDUIALU-UHFFFAOYSA-M sodium;hydron;difluoride Chemical compound F.[F-].[Na+] BFXAWOHHDUIALU-UHFFFAOYSA-M 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 125000003277 amino group Chemical group 0.000 description 2
- 229940111685 dibasic potassium phosphate Drugs 0.000 description 2
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 2
- ZPWVASYFFYYZEW-UHFFFAOYSA-L dipotassium hydrogen phosphate Chemical compound [K+].[K+].OP([O-])([O-])=O ZPWVASYFFYYZEW-UHFFFAOYSA-L 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 description 2
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 2
- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 description 2
- 239000004137 magnesium phosphate Substances 0.000 description 2
- 229960002261 magnesium phosphate Drugs 0.000 description 2
- 229910000157 magnesium phosphate Inorganic materials 0.000 description 2
- 235000010994 magnesium phosphates Nutrition 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229940111688 monobasic potassium phosphate Drugs 0.000 description 2
- 235000019796 monopotassium phosphate Nutrition 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 2
- 239000007836 KH2PO4 Substances 0.000 description 1
- 206010073310 Occupational exposures Diseases 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910000396 dipotassium phosphate Inorganic materials 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- HZZOEADXZLYIHG-UHFFFAOYSA-N magnesiomagnesium Chemical compound [Mg][Mg] HZZOEADXZLYIHG-UHFFFAOYSA-N 0.000 description 1
- 159000000003 magnesium salts Chemical class 0.000 description 1
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 1
- 231100000675 occupational exposure Toxicity 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 235000003270 potassium fluoride Nutrition 0.000 description 1
- 239000011698 potassium fluoride Substances 0.000 description 1
- CMZUMMUJMWNLFH-UHFFFAOYSA-N sodium metavanadate Chemical compound [Na+].[O-][V](=O)=O CMZUMMUJMWNLFH-UHFFFAOYSA-N 0.000 description 1
- 229940062627 tribasic potassium phosphate Drugs 0.000 description 1
- LWIHDJKSTIGBAC-UHFFFAOYSA-K tripotassium phosphate Chemical compound [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 1
- 229910000404 tripotassium phosphate Inorganic materials 0.000 description 1
- 229910000166 zirconium phosphate Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
- C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/40—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates
- C23C22/44—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates containing also fluorides or complex fluorides
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
- C23C22/77—Controlling or regulating of the coating process
Definitions
- the present invention relates to a corrosion resistant, chromate-free, phosphate-fluoride conversion coating, with or without vanadate, for a product formed from magnesium or a magnesium alloy and to a coating solution for use in a coating process.
- Magnesium alloys are light and strong, but very vulnerable to corrosion due to the reactive nature of magnesium. Magnesium alloys are protected from corrosion in all practical applications.
- a commonly used, low cost, corrosion resistant treatment for magnesium alloys is a dichromate based conversion coating. While dichromate based conversion coatings provide good corrosion protection, they are based on a chemical compound (hexavalent chromium) that has many occupational exposure risks.
- a non-chromate, corrosion resistant magnesium conversion coating is required to meet industry demands.
- U.S. Patent No. 5,683,522 to Joesten Another treatment for protecting magnesium or magnesium alloy products is shown in U.S. Patent No. 5,683,522 to Joesten.
- a paint adherent and corrosion resistant coating of magnesium phosphate and magnesium fluoride is applied to a product formed from a magnesium alloy.
- the process for applying the coating involves immersing the magnesium alloy product in a solution having phosphate and fluoride ions.
- This treatment while providing a barrier film and very good paint adhesion, does not include electrochemically active ingredients to suppress corrosion.
- U.S. Patent Application Publication No. 2003/0150525 discloses an improved phosphate-fluoride corrosion coating for magnesium and process for applying same.
- a chromate-free, phosphate-fluoride conversion coating, with or without vanadate, formed on a magnesium or a magnesium alloy substrate includes an active corrosion inhibitor selected from the group consisting of organo-phosphonic acids.
- the phosphonic acid group reacts with the magnesium metal of the substrate to form an insoluble salt.
- the preferred organo-phosphonic acids used as corrosion inhibitors in accordance with the present invention are selected from the group consisting of straight chain or branched amino alkyl phosphonic acids, straight chain or branched alkyl phoshonic acids, and triphosphonic acids, particularly, nitrilotris (methylene) triphosphonic acid (NTMP).
- the corrosion inhibitor includes amino alkyl phosphonic acids, the amine group can interact with vanadate ions in the coating solution to increase the vanadate incorporation into the conversion coating.
- a solution for forming a chromate-free, corrosion resistant coating on a magnesium or magnesium alloy substrate comprises a solution having phosphate and fluoride ions and, an active corrosion inhibitor selected from the group consisting of organo-phosphonic acids.
- the solution of the present invention may optionally include vanadate anions.
- the active corrosion inhibitor is selected from the group consisting of straight chained or branched amino-alkyl phosphonic acids, straight chained or branched alkyl phosphonic acids, triphosphonic acids, and mixtures thereof.
- a particular useful triphosphonic acid comprises nitrilotris (methylene) triphosphonic acid (NTMP).
- the chromate-free solution include phosphate and fluoride ions.
- Phosphate and fluoride ions are present in an amount of between about 1 g/L to 50 g/L and 1 g/L to 10 g/L, respectively, preferably between 10 g/L to 25 g/L and 3 g/L to 5 g/L, respectively. It is important in the present invention to control the pH of the solution and this is achieved by the amount of phosphate ions and fluoride ions in the solution.
- the pH of the solution is preferably in the range of 5 to 7.
- the particular phosphate and fluoride compounds employed in forming the solution having the appropriate pH is disclosed in detail in U.S. Patent Application Publication No.
- suitable phosphate compounds include monobasic potassium phosphate (KH 2 PO 4 ), dibasic potassium phosphate (K 2 HPO 4 ), tribasic potassium phosphate (K 3 PO 4 ), or phosphoric acid (H 3 PO 4 ), or combinations of these alternatives.
- a preferred embodiment is a combination of monobasic potassium phosphate and dibasic potassium phosphate.
- Suitable fluoride compounds include sodium bifluoride (NaHF 2 ). In a preferred embodiment, the concentration is provided at about 0.3-0.5% by weight sodium bifluoride. Other fluoride compounds, such as potassium fluoride or hydrofluoric acid, may also be used.
- the corrosion inhibitor is present in the solution in an amount of between about 1 ppm to 1 wt%, preferably 10 ppm to 0.5 wt%.
- the corrosion inhibitor is in the form of an organo-phosphonic acid.
- organo-phosphonic acids include straight chained and branched amino-alkyl phosphonic acids, straight chained or branched alkyl phosphonic acids and triphosphonic acids.
- a particularly useful triphosphonic acid is nitrilotris (methylene) triphosphonic acid (NTMP).
- the solution may optionally include vanadate anions.
- Sodium vanadate is a suitable source of vanadate ions for the solution of the present invention.
- the vanadate ions are present in an amount of between about 1.0 g/l to 5.0 g/l. It has been found that the vanadate anions interact with the amine group of the amino alkyl phosphonic acids increase incorporation of the vanadate into the conversion coating thereby improving the coating performance.
- the phosphonic acid groups of the corrosion inhibitor react with the magnesium metal substrate to form insoluble salts which improve corrosion performance.
- the preferred chromate-free solution comprises phosphate ions in an amount of between 10 to 25 g/L, fluoride ions in an amount of between 3 g/L to 5 g/L, vanadate anions in an amount of between 1 g/L to 5 g/L, and the corrosion inhibitor in an amount of between 10 ppm to 0.5 wt%.
- a magnesium or magnesium alloy substrate having a conversion coating in accordance with the present invention comprises mostly magnesium phosphate and magnesium fluoride. It is believed that the amino alkyl phosphonic acid will form insoluble magnesium salt as part of the conversion coating. This component will increase the interaction of vanadium with conversion coating, therefore increase vanadium content in the coating, should vanadium is used as corrosion inhibitor as well.
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- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Treatment Of Metals (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
A chromate-free, phosphate-fluoride conversion coating,
with or without vanadate, formed on a magnesium or a magnesium
alloy substrate, includes an active corrosion inhibitor selected
from the group consisting of organo-phosphonic acids. The
phosphonic acid group reacts with the magnesium metal of the
substrate to form an insoluble salt.
Description
- The present invention relates to a corrosion resistant, chromate-free, phosphate-fluoride conversion coating, with or without vanadate, for a product formed from magnesium or a magnesium alloy and to a coating solution for use in a coating process.
- Magnesium alloys are light and strong, but very vulnerable to corrosion due to the reactive nature of magnesium. Magnesium alloys are protected from corrosion in all practical applications. A commonly used, low cost, corrosion resistant treatment for magnesium alloys is a dichromate based conversion coating. While dichromate based conversion coatings provide good corrosion protection, they are based on a chemical compound (hexavalent chromium) that has many occupational exposure risks. A non-chromate, corrosion resistant magnesium conversion coating is required to meet industry demands.
- Another treatment for protecting magnesium or magnesium alloy products is shown in U.S. Patent No. 5,683,522 to Joesten. In this treatment, a paint adherent and corrosion resistant coating of magnesium phosphate and magnesium fluoride is applied to a product formed from a magnesium alloy. The process for applying the coating involves immersing the magnesium alloy product in a solution having phosphate and fluoride ions. This treatment while providing a barrier film and very good paint adhesion, does not include electrochemically active ingredients to suppress corrosion. U.S. Patent Application Publication No. 2003/0150525 discloses an improved phosphate-fluoride corrosion coating for magnesium and process for applying same.
- It is an object of the present invention to provide an improved chromate-free corrosion resistant conversion coating for magnesium and magnesium alloy products.
- It is a further object of the present invention to provide a coating solution for forming the chromate-free corrosion resistant coating.
- The foregoing objects are attained by the present invention.
- In accordance with the present invention, a chromate-free, phosphate-fluoride conversion coating, with or without vanadate, formed on a magnesium or a magnesium alloy substrate, includes an active corrosion inhibitor selected from the group consisting of organo-phosphonic acids. The phosphonic acid group reacts with the magnesium metal of the substrate to form an insoluble salt. The preferred organo-phosphonic acids used as corrosion inhibitors in accordance with the present invention are selected from the group consisting of straight chain or branched amino alkyl phosphonic acids, straight chain or branched alkyl phoshonic acids, and triphosphonic acids, particularly, nitrilotris (methylene) triphosphonic acid (NTMP). When the corrosion inhibitor includes amino alkyl phosphonic acids, the amine group can interact with vanadate ions in the coating solution to increase the vanadate incorporation into the conversion coating.
- Other details of the magnesium-magnesium alloy conversion coating of the present invention, as well as objects and advantages attended thereto, are set forth in the following detailed description.
- In accordance with the present invention, a solution for forming a chromate-free, corrosion resistant coating on a magnesium or magnesium alloy substrate comprises a solution having phosphate and fluoride ions and, an active corrosion inhibitor selected from the group consisting of organo-phosphonic acids.
- The solution of the present invention may optionally include vanadate anions. The active corrosion inhibitor is selected from the group consisting of straight chained or branched amino-alkyl phosphonic acids, straight chained or branched alkyl phosphonic acids, triphosphonic acids, and mixtures thereof. A particular useful triphosphonic acid comprises nitrilotris (methylene) triphosphonic acid (NTMP).
- As noted above, the chromate-free solution include phosphate and fluoride ions. Phosphate and fluoride ions are present in an amount of between about 1 g/L to 50 g/L and 1 g/L to 10 g/L, respectively, preferably between 10 g/L to 25 g/L and 3 g/L to 5 g/L, respectively. It is important in the present invention to control the pH of the solution and this is achieved by the amount of phosphate ions and fluoride ions in the solution. The pH of the solution is preferably in the range of 5 to 7. The particular phosphate and fluoride compounds employed in forming the solution having the appropriate pH is disclosed in detail in U.S. Patent Application Publication No. 2003/0150525 to which suitable reference can be made. As mentioned therein, suitable phosphate compounds include monobasic potassium phosphate (KH2PO4), dibasic potassium phosphate (K2HPO4), tribasic potassium phosphate (K3PO4), or phosphoric acid (H3PO4), or combinations of these alternatives. A preferred embodiment is a combination of monobasic potassium phosphate and dibasic potassium phosphate. Suitable fluoride compounds include sodium bifluoride (NaHF2). In a preferred embodiment, the concentration is provided at about 0.3-0.5% by weight sodium bifluoride. Other fluoride compounds, such as potassium fluoride or hydrofluoric acid, may also be used.
- In accordance with the present invention, the corrosion inhibitor is present in the solution in an amount of between about 1 ppm to 1 wt%, preferably 10 ppm to 0.5 wt%. The corrosion inhibitor is in the form of an organo-phosphonic acid. Preferred organo-phosphonic acids include straight chained and branched amino-alkyl phosphonic acids, straight chained or branched alkyl phosphonic acids and triphosphonic acids. A particularly useful triphosphonic acid is nitrilotris (methylene) triphosphonic acid (NTMP).
- In accordance with the present invention, the solution may optionally include vanadate anions. Sodium vanadate is a suitable source of vanadate ions for the solution of the present invention. In accordance with the present invention, the vanadate ions are present in an amount of between about 1.0 g/l to 5.0 g/l. It has been found that the vanadate anions interact with the amine group of the amino alkyl phosphonic acids increase incorporation of the vanadate into the conversion coating thereby improving the coating performance. In addition, the phosphonic acid groups of the corrosion inhibitor react with the magnesium metal substrate to form insoluble salts which improve corrosion performance.
- The preferred chromate-free solution comprises phosphate ions in an amount of between 10 to 25 g/L, fluoride ions in an amount of between 3 g/L to 5 g/L, vanadate anions in an amount of between 1 g/L to 5 g/L, and the corrosion inhibitor in an amount of between 10 ppm to 0.5 wt%.
- A magnesium or magnesium alloy substrate having a conversion coating in accordance with the present invention comprises mostly magnesium phosphate and magnesium fluoride. It is believed that the amino alkyl phosphonic acid will form insoluble magnesium salt as part of the conversion coating. This component will increase the interaction of vanadium with conversion coating, therefore increase vanadium content in the coating, should vanadium is used as corrosion inhibitor as well.
- It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its scope as defined by the claims.
Claims (8)
- A solution for forming a chromate-free, corrosion resistant coating on a product formed from magnesium or a magnesium alloy, comprising:the solution having phosphate and fluoride ions; andan active corrosion inhibitor selected from the group consisting of organo-phosphonic acids.
- A solution according to claim 1, wherein the organo-phosphonic acid is selected from the group consisting of straight chained amino-alkyl phosphonic acids, branched amino-alkyl phosphonic acids, straight chained alkyl phosphonic acids, branched alkyl phosphonic acids, triphosphonic acids, and mixtures thereof.
- A solution according to claim 2, wherein the triphosphonic acids comprise nitrilotris (methylene) triphosphonic acid (NTMP).
- A solution according to any one of the preceding claims, wherein the solution includes vanadate.
- A solution according to any one of the preceding claims, wherein the solution comprises 1 ppm to 1 wt% of the corrosion inhibitor, preferably 10 ppm to 0.5 wt%.
- A solution according to claim 5, wherein phosphate ions are present in an amount of between 1 g/L to 50 g/L, preferably between 10 g/L to 25 g/L, and the fluoride ions are present in an amount of 1 g/L to 10 g/L, preferably 3 g/L to 5 g/L.
- A process for preparing a corrosion-resistant, chromate free, coating on a magnesium or magnesium alloy substrate comprising treating the substrate with a solution as defined in any one of the preceding claims, wherein the phosphonic acid group reacts with magnesium metal forming an insoluble salt.
- An article comprising a magnesium or magnesium alloy substrate and a corrosion resistant coating obtainable by the process as defined in claim 7.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US601247 | 2003-06-20 | ||
| US10/601,247 US20040256030A1 (en) | 2003-06-20 | 2003-06-20 | Corrosion resistant, chromate-free conversion coating for magnesium alloys |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP1489199A1 true EP1489199A1 (en) | 2004-12-22 |
Family
ID=33418585
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP04253681A Withdrawn EP1489199A1 (en) | 2003-06-20 | 2004-06-18 | Corrosion resistant coating composition and process and coated magnesium |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US20040256030A1 (en) |
| EP (1) | EP1489199A1 (en) |
| JP (1) | JP2005008985A (en) |
| KR (1) | KR100611288B1 (en) |
| CN (1) | CN100339507C (en) |
| PL (1) | PL368625A1 (en) |
| SG (1) | SG117497A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1950325A3 (en) * | 2007-01-19 | 2010-02-03 | Nihon Hyomen Kagaku Kabushiki Kaisha | Chromium-free solution for treating metal surfaces |
| TWI394863B (en) * | 2007-12-27 | 2013-05-01 | Kansai Paint Co Ltd | Metal surface treatment composition, and surface-treated metal material with metal surface treatment layer obtained from the metal surface treatment composition |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0507887D0 (en) * | 2005-04-20 | 2005-05-25 | Rohm & Haas Elect Mat | Immersion method |
| US20090004486A1 (en) | 2007-06-27 | 2009-01-01 | Sarah Arsenault | Corrosion inhibiting additive |
| WO2009072905A2 (en) * | 2007-12-04 | 2009-06-11 | Katja Products Limited | Surface coating |
| JP4908456B2 (en) | 2008-06-02 | 2012-04-04 | パンパシフィック・カッパー株式会社 | Copper smelting method |
| US20130014670A1 (en) * | 2010-04-01 | 2013-01-17 | Commissariat a I'Energie Atomique et Aux Energies Altematives | Use of anticorrosion agents for conditioning magnesium metal, conditioning material thus obtained and preparation process |
| JP5595874B2 (en) * | 2010-11-04 | 2014-09-24 | 三井金属鉱業株式会社 | Magnesium alloy surface treatment method |
| JP6089053B2 (en) * | 2015-03-16 | 2017-03-01 | 有限会社エスク | Biodegradable metal surface modified stent with anticorrosive ability |
| KR102142783B1 (en) * | 2018-11-30 | 2020-08-07 | 주식회사 포스코 | Surface-treating composition for magnesium or magnesium alloy and surface-treated magnesium or magnesium alloy using the same |
| AU2022444558B2 (en) * | 2022-03-03 | 2025-11-13 | Nippon Steel Corporation | Surface-treated steel sheet |
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| WO1995010641A1 (en) * | 1993-10-15 | 1995-04-20 | Circle-Prosco, Inc. | Conversion coatings for metal surfaces |
| US5449415A (en) * | 1993-07-30 | 1995-09-12 | Henkel Corporation | Composition and process for treating metals |
| US5683522A (en) * | 1995-03-30 | 1997-11-04 | Sundstrand Corporation | Process for applying a coating to a magnesium alloy product |
| DE19754108A1 (en) * | 1997-12-05 | 1999-06-10 | Henkel Kgaa | Chromium-free anti-corrosion agent and anti-corrosion process |
| DE19923084A1 (en) * | 1999-05-20 | 2000-11-23 | Henkel Kgaa | Chromium-free corrosion protection agent for coating metallic substrates contains hexafluoro anions, phosphoric acid, metal compound, film-forming organic polymer or copolymer and organophosphonic acid |
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| US4017334A (en) * | 1973-10-04 | 1977-04-12 | Oxy Metal Industries Corporation | Process for treating aluminum cans |
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| US4308079A (en) * | 1980-06-16 | 1981-12-29 | Martin Marietta Corporation | Durability of adhesively bonded aluminum structures and method for inhibiting the conversion of aluminum oxide to aluminum hydroxide |
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| US6692583B2 (en) * | 2002-02-14 | 2004-02-17 | Jon Bengston | Magnesium conversion coating composition and method of using same |
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- 2003-06-20 US US10/601,247 patent/US20040256030A1/en not_active Abandoned
-
2004
- 2004-06-15 KR KR1020040043886A patent/KR100611288B1/en not_active Expired - Fee Related
- 2004-06-15 SG SG200403770A patent/SG117497A1/en unknown
- 2004-06-18 PL PL04368625A patent/PL368625A1/en not_active Application Discontinuation
- 2004-06-18 EP EP04253681A patent/EP1489199A1/en not_active Withdrawn
- 2004-06-18 JP JP2004180425A patent/JP2005008985A/en active Pending
- 2004-06-18 CN CNB2004100714667A patent/CN100339507C/en not_active Expired - Fee Related
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| US2312855A (en) * | 1940-09-07 | 1943-03-02 | Parker Rust Proof Co | Method of coating aluminum |
| US3459600A (en) * | 1966-11-07 | 1969-08-05 | Todco Chem Co Inc | Novel zinc coating composition and method |
| EP0084593A1 (en) * | 1982-01-25 | 1983-08-03 | Pennwalt Corporation | Phosphate conversion coatings for metals with reduced weights and crystal sizes |
| US5143562A (en) * | 1991-11-01 | 1992-09-01 | Henkel Corporation | Broadly applicable phosphate conversion coating composition and process |
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| WO1995010641A1 (en) * | 1993-10-15 | 1995-04-20 | Circle-Prosco, Inc. | Conversion coatings for metal surfaces |
| US5683522A (en) * | 1995-03-30 | 1997-11-04 | Sundstrand Corporation | Process for applying a coating to a magnesium alloy product |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1950325A3 (en) * | 2007-01-19 | 2010-02-03 | Nihon Hyomen Kagaku Kabushiki Kaisha | Chromium-free solution for treating metal surfaces |
| US8980016B2 (en) | 2007-01-19 | 2015-03-17 | Nihon Hyomen Kagaku Kabushiki Kaisha | Chromium-free solution for treating metal surfaces |
| TWI394863B (en) * | 2007-12-27 | 2013-05-01 | Kansai Paint Co Ltd | Metal surface treatment composition, and surface-treated metal material with metal surface treatment layer obtained from the metal surface treatment composition |
Also Published As
| Publication number | Publication date |
|---|---|
| KR100611288B1 (en) | 2006-08-10 |
| CN100339507C (en) | 2007-09-26 |
| KR20040110097A (en) | 2004-12-29 |
| JP2005008985A (en) | 2005-01-13 |
| SG117497A1 (en) | 2005-12-29 |
| US20040256030A1 (en) | 2004-12-23 |
| CN1572904A (en) | 2005-02-02 |
| PL368625A1 (en) | 2004-12-27 |
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