US20210262097A1 - Preparation for pre-treating surfaces by chemically converting oxide layers of titanium or titanium alloys - Google Patents
Preparation for pre-treating surfaces by chemically converting oxide layers of titanium or titanium alloys Download PDFInfo
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- US20210262097A1 US20210262097A1 US17/254,901 US201917254901A US2021262097A1 US 20210262097 A1 US20210262097 A1 US 20210262097A1 US 201917254901 A US201917254901 A US 201917254901A US 2021262097 A1 US2021262097 A1 US 2021262097A1
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- 239000010936 titanium Substances 0.000 title claims abstract description 37
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 229910052719 titanium Inorganic materials 0.000 title claims abstract description 35
- 238000002360 preparation method Methods 0.000 title claims abstract description 34
- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 24
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 23
- 101100345345 Arabidopsis thaliana MGD1 gene Proteins 0.000 claims abstract description 12
- OHOTVSOGTVKXEL-UHFFFAOYSA-K trisodium;2-[bis(carboxylatomethyl)amino]propanoate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)C(C)N(CC([O-])=O)CC([O-])=O OHOTVSOGTVKXEL-UHFFFAOYSA-K 0.000 claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims description 10
- 239000011148 porous material Substances 0.000 claims description 7
- 239000002562 thickening agent Substances 0.000 claims description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 6
- 238000007654 immersion Methods 0.000 claims description 4
- 229920001817 Agar Polymers 0.000 claims description 2
- 241000206672 Gelidium Species 0.000 claims description 2
- 235000010419 agar Nutrition 0.000 claims description 2
- 235000010493 xanthan gum Nutrition 0.000 claims description 2
- 239000000230 xanthan gum Substances 0.000 claims description 2
- 229920001285 xanthan gum Polymers 0.000 claims description 2
- 229940082509 xanthan gum Drugs 0.000 claims description 2
- 230000007774 longterm Effects 0.000 description 9
- 229910000883 Ti6Al4V Inorganic materials 0.000 description 8
- 239000010410 layer Substances 0.000 description 8
- 238000011282 treatment Methods 0.000 description 7
- 238000002048 anodisation reaction Methods 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- CIEZZGWIJBXOTE-UHFFFAOYSA-N 2-[bis(carboxymethyl)amino]propanoic acid Chemical compound OC(=O)C(C)N(CC(O)=O)CC(O)=O CIEZZGWIJBXOTE-UHFFFAOYSA-N 0.000 description 2
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000007743 anodising Methods 0.000 description 2
- 239000000872 buffer Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 239000003599 detergent Substances 0.000 description 2
- 238000004851 dishwashing Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 238000004381 surface treatment Methods 0.000 description 2
- HRXKRNGNAMMEHJ-UHFFFAOYSA-K trisodium citrate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O HRXKRNGNAMMEHJ-UHFFFAOYSA-K 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- LCOBNBPKWCKAKF-UHFFFAOYSA-N 1-[3,6-dihydroxy-2,4-bis(phenylmethoxy)phenyl]ethanone Chemical compound OC1=C(OCC=2C=CC=CC=2)C(C(=O)C)=C(O)C=C1OCC1=CC=CC=C1 LCOBNBPKWCKAKF-UHFFFAOYSA-N 0.000 description 1
- FZIPCQLKPTZZIM-UHFFFAOYSA-N 2-oxidanylpropane-1,2,3-tricarboxylic acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O.OC(=O)CC(O)(C(O)=O)CC(O)=O FZIPCQLKPTZZIM-UHFFFAOYSA-N 0.000 description 1
- 102000013142 Amylases Human genes 0.000 description 1
- 108010065511 Amylases Proteins 0.000 description 1
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 208000010201 Exanthema Diseases 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 102000035195 Peptidases Human genes 0.000 description 1
- 108091005804 Peptidases Proteins 0.000 description 1
- 239000004365 Protease Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000012790 adhesive layer Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 235000019418 amylase Nutrition 0.000 description 1
- 229940025131 amylases Drugs 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
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- 239000008139 complexing agent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000013527 degreasing agent Substances 0.000 description 1
- 238000005237 degreasing agent Methods 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 229940088598 enzyme Drugs 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 201000005884 exanthem Diseases 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- -1 fluorine ions Chemical class 0.000 description 1
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 1
- 238000013532 laser treatment Methods 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- PNSWKXISZRTMSD-UHFFFAOYSA-K pentasodium;phosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[Na+].[O-]P([O-])([O-])=O PNSWKXISZRTMSD-UHFFFAOYSA-K 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 206010037844 rash Diseases 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005488 sandblasting Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000012360 testing method Methods 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
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
- C23G1/20—Other heavy metals
- C23G1/205—Other heavy metals refractory metals
-
- 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
- C23C22/60—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 alkaline aqueous solutions with pH greater than 8
- C23C22/64—Treatment of refractory metals or alloys based thereon
Definitions
- the invention relates to a preparation for surface pretreatment by chemically converting oxide layers of titanium or titanium alloys, and to a process for the surface pretreatment of articles composed of titanium or titanium alloys comprising contacting the article composed of titanium or titanium alloys with such a preparation.
- titanium in the aerospace industry has increased in the last 30 years, accounting for up to 15% of the structural weight in the most recent aircraft generations (e.g., Airbus 350 XWB, Boeing 787).
- the reasons for the increase could be attributable to the need to replace aluminum structures at connection points between composite materials and metal structures due to problems with galvanic corrosion.
- the corrosion resistance and the strength-to-weight ratio of titanium and its alloys make it interesting for new design concepts. Titanium materials exhibit problems with long-term stable adhesion. Rivet rashes on titanium rivet heads, discoloration at crack arrestors or delamination of fiber metal laminates are some examples of this problem.
- Mechanical surface treatments such as sandblasting are mainly used to produce a macroscopically rough surface and to remove residues.
- chromic acid anodization (CAA) using small amounts of fluorides in the electrolyte.
- the nanostructures are produced by localized chemical dissolution (fluorine ions) with controlled field-assisted oxidation and dissolution reactions.
- CAA results in a high bond stability.
- alkaline electrolytes are also discussed as a pretreatment for the structural bonding of titanium.
- Sodium hydroxide-based electrolytes porous oxide layers could be created on titanium.
- Sodium hydroxide anodization can achieve good durability of adhesive bonds in the case of moisture and stress.
- DE 3427543 discloses the use of electrolytes with sodium hydroxide with complexing agents such as ethylenediaminetetraacetic acid (EDTA) in order to increase the dissolution rate.
- EDTA ethylenediaminetetraacetic acid
- This NaTESi process can be used to achieve a highly porous oxide layer and good long-term stability.
- DE102011106764B4 discloses an anodizing process based on sodium hydroxide, methylglycinediacetic acid and disodium tartrate dihydrate, and also pentasodium phosphate.
- Anodization processes are limited in terms of application. Due to physics (Faraday effect), they cannot be used in pipes, cavities or channels without additional effort. Shadow effects might lead to development of an inhomogeneous oxide layer as well. The anodization parameters frequently have to be adapted to each titanium alloy used.
- Laser treatments can generate a nanostructured titanium surface which results in good long-term adhesion.
- the laser is a line-of-sight method, perpendicular access to the surface has to be guaranteed. This is not possible without significant effort in the case of complex parts.
- a laser also involves a melting process of the surface which even for nanosecond-pulsed systems causes a heat-affected zone having different properties compared to the base material.
- a preparation for the surface pretreatment of titanium or titanium alloys containing 200 to 400 g/l NaOH and 10 to 150 g/l MGDA in water, wherein the preparation has a pH of at least 12, preferably at least 13, remedies the disadvantages of the prior art.
- surface pretreatment is understood to mean a chemical conversion of oxide layers of the titanium or titanium alloy. Based on atomic %, titanium alloys predominantly consist of titanium. The NaOH content advantageously does not exceed the value of 590 g/l.
- Using the preparation according to the invention makes it possible to convert the oxide layer present, which has formed naturally or can be produced artificially, into a nanostructured porous surface.
- Such nanostructured porous surfaces can also be referred to as a nanostructured network. These nanostructured porous surfaces can enable long-term stable adhesion of organic coatings on titanium substrates.
- the preparation according to the invention is free of buffers, such as citrate-citric acid buffer, does not contain any sulfate, and does not contain any enzymes, in particular any amylases or proteases.
- the surfactant content is very low and does not exceed the value of 5% by weight based on MGDA.
- the preparation according to the invention is additionally free of whiteners and silicates.
- the preparation according to the invention can be used to treat surfaces of titanium or titanium alloys electrolessly and/or at low temperature.
- MGDA is methylglycinediacetic acid, and this also means salts of this acid such as the trisodium salt.
- the acid has the structural formula
- Amounts indicated in this document are based on the trisodium salt of MGDA.
- the invention also comprises a process for the surface pretreatment of articles composed of titanium or titanium alloys, comprising contacting the article composed of titanium or titanium alloys with a preparation containing 200 to 400 g/l NaOH and 10 to 150 g/l MGDA in water, wherein the content of further substances is less than 1 g/l and the pH of the preparation has a pH of at least 12, preferably at least 13, for 5 to 60 minutes at 20 to 80° C.
- Contacting can in this case be immersion, spraying, coating.
- the process according to the invention makes it possible to produce nanostructures having dimensions of below 100 nm, and hence to produce a mechanical and chemical anchoring by means of an enlarged surface area, which improves the durability and adhesion properties of titanium or titanium alloys thus treated.
- the fluoride content is not detectable or is less than 0.001% by weight, based on the fluoride present in the preparation used. It is further preferable if the content of NaOH is 300 to 375 g/l, preferably 350 g/l, and the content of MGDA is 30 to 100 g/l, preferably 60 g/l. It is further preferable if the preparation according to the invention has a content of polymeric thickeners. It is preferable here if the thickeners used are xanthan gum or agar-agar and/or the thickener is present in concentrations of 2 to 40 g/l, preferably 10 to 15 g/l.
- the content of further substances in the preparation according to the invention is less than 0.5 g/l, preferably 0.3 g/l. It is further preferable if the contacting is effected by immersion. It is further preferable if the contacting is effected for 10 to 30 minutes at 40 to 70° C. It is further preferable if the contacting is effected for 20 minutes at 60° C.
- the process according to the invention particularly preferably comprises a pretreatment for ensuring the wettability of the titanium or titanium alloys, in particular, with surface-active substances.
- the process according to the invention further preferably comprises an aftertreatment for washing off the preparation according to the invention, in particular, by washing off with demineralized water.
- a product according to the present invention is an article composed of titanium or titanium alloys obtainable by a process according to the invention or using a preparation according to the invention. It is preferable if the article according to the invention composed of titanium or titanium alloys having a porous layer at the surface, wherein the pores are predominantly open, have a number-average pore size of less than 100 nm, preferably 30 to 70 nm.
- the invention further comprises an aircraft, in particular, an aircraft comprising an article according to the invention composed of titanium or titanium alloys.
- the examples show various treatments of various titanium alloys. The conditions are stated in each case. Prior to the treatment, the material samples are washed with isopropanol or with an alkaline degreasing agent (Metaclean T2001, experiments 7 and 8 only). After drying, the samples were treated with the aqueous solutions specified by immersion without movement or stirring. The solutions had a pH of approx. 14. After the treatment, the surface obtained was assessed visually. An iridescent surface indicates a surface modification with characteristic dimensions in the region of the wavelength of light (nanostructured surface).
- Ti6Al4V 240 30 60 15 ++ green/blue iridescent surface 2 Ti6Al4V 240 60 60 15 ++ iridescent surface 3 Ti6Al4V 350 120 75 15 ++ iridescent surface 4 Ti6Al4V 350 — 65 15 ⁇ surface not nanostructured 5 Ti6Al4V 350 30 65 15 ++ iridescent surface 6 Ti6Al4V 450 30 65 15 + yellowish iridescent surface with violet specks 7 Ti6Al4V 200 30 65 15 ++ green/blue iridescent surface 8 Cp-Ti 200 30 65 15 ++ violet/blue iridescent surface 9 Ti6Al4V 350 60 60 15 ++ iridescent surface
- SEM images of the surface obtained in experiment 5 show a sponge-like surface structure with pore sizes of 30 to 100 nm.
- the pore walls are of an open and irregularly network-like configuration.
- roller peel test in accordance with DIN 2243-2 showed exceptional adhesion compared to untreated titanium sheet: at room temperature there was exclusively failure of the adhesive layer and not detachment of the bond, and at ⁇ 55° C. there was 95% failure of the bond.
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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)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
- Chemical Treatment Of Metals (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
Description
- This application claims the benefit of the International Application No. PCT/EP2019/067602, filed on Jul. 1, 2019, and of the German patent application No. 102018005156.1 filed on Jun. 29, 2018, the entire disclosures of which are incorporated herein by way of reference.
- The invention relates to a preparation for surface pretreatment by chemically converting oxide layers of titanium or titanium alloys, and to a process for the surface pretreatment of articles composed of titanium or titanium alloys comprising contacting the article composed of titanium or titanium alloys with such a preparation.
- The use of titanium in the aerospace industry has increased in the last 30 years, accounting for up to 15% of the structural weight in the most recent aircraft generations (e.g., Airbus 350 XWB, Boeing 787). The reasons for the increase could be attributable to the need to replace aluminum structures at connection points between composite materials and metal structures due to problems with galvanic corrosion. The corrosion resistance and the strength-to-weight ratio of titanium and its alloys make it interesting for new design concepts. Titanium materials exhibit problems with long-term stable adhesion. Rivet rashes on titanium rivet heads, discoloration at crack arrestors or delamination of fiber metal laminates are some examples of this problem.
- Surface treatment is therefore the most important step for ensuring durable connections. To increase durability, treatments for the surface modification of titanium have been developed.
- Mechanical surface treatments such as sandblasting are mainly used to produce a macroscopically rough surface and to remove residues.
- Physical (e.g., plasma or laser) or wet-chemical treatments (e.g., etching or anodizing) are usually used to produce long-term stable adhesive bonds. Anodization processes are used in the aviation industry for the pretreatment of titanium. The most common method for obtaining porous oxide layers is chromic acid anodization (CAA) using small amounts of fluorides in the electrolyte. The nanostructures are produced by localized chemical dissolution (fluorine ions) with controlled field-assisted oxidation and dissolution reactions. CAA results in a high bond stability. Besides anodization in acidic electrolytes, alkaline electrolytes are also discussed as a pretreatment for the structural bonding of titanium. Using sodium hydroxide-based electrolytes, porous oxide layers could be created on titanium. Sodium hydroxide anodization can achieve good durability of adhesive bonds in the case of moisture and stress. DE 3427543 discloses the use of electrolytes with sodium hydroxide with complexing agents such as ethylenediaminetetraacetic acid (EDTA) in order to increase the dissolution rate. This NaTESi process can be used to achieve a highly porous oxide layer and good long-term stability.
- DE102011106764B4 discloses an anodizing process based on sodium hydroxide, methylglycinediacetic acid and disodium tartrate dihydrate, and also pentasodium phosphate.
- Sol-gel processes, the Rocatec process and Pyrosil treatment are also known.
- There is no prior art process that can ensure long-term stable adhesion to titanium without using an energy source such as lasers or an electric field or chemical components which are not regulation-compliant over the long term.
- Anodization processes are limited in terms of application. Due to physics (Faraday effect), they cannot be used in pipes, cavities or channels without additional effort. Shadow effects might lead to development of an inhomogeneous oxide layer as well. The anodization parameters frequently have to be adapted to each titanium alloy used.
- Laser treatments can generate a nanostructured titanium surface which results in good long-term adhesion. However, since the laser is a line-of-sight method, perpendicular access to the surface has to be guaranteed. This is not possible without significant effort in the case of complex parts. A laser also involves a melting process of the surface which even for nanosecond-pulsed systems causes a heat-affected zone having different properties compared to the base material.
- There is no prior art process that can ensure long-term stable adhesion to titanium without using an energy source such as lasers or an electric field or chemical components which are not regulation-compliant over the long term.
- It has now been found, in a manner completely surprising to the person skilled in the art, that a preparation for the surface pretreatment of titanium or titanium alloys containing 200 to 400 g/l NaOH and 10 to 150 g/l MGDA in water, wherein the preparation has a pH of at least 12, preferably at least 13, remedies the disadvantages of the prior art. In the context of the present invention, surface pretreatment is understood to mean a chemical conversion of oxide layers of the titanium or titanium alloy. Based on atomic %, titanium alloys predominantly consist of titanium. The NaOH content advantageously does not exceed the value of 590 g/l. Using the preparation according to the invention makes it possible to convert the oxide layer present, which has formed naturally or can be produced artificially, into a nanostructured porous surface. Such nanostructured porous surfaces can also be referred to as a nanostructured network. These nanostructured porous surfaces can enable long-term stable adhesion of organic coatings on titanium substrates. In addition, the preparation according to the invention is free of buffers, such as citrate-citric acid buffer, does not contain any sulfate, and does not contain any enzymes, in particular any amylases or proteases. The surfactant content is very low and does not exceed the value of 5% by weight based on MGDA. The preparation according to the invention is additionally free of whiteners and silicates. The preparation according to the invention can be used to treat surfaces of titanium or titanium alloys electrolessly and/or at low temperature. MGDA is methylglycinediacetic acid, and this also means salts of this acid such as the trisodium salt. The acid has the structural formula
-
(HOOC-CH2-)2N-CH(CH3)-COOH. - It is a biodegradable water-softening additive for dishwashing detergents which was developed in order to avoid the less environmentally compatible use of phosphates or poorly degradable water softeners in machine dishwashing detergents.
- Amounts indicated in this document are based on the trisodium salt of MGDA.
- The invention also comprises a process for the surface pretreatment of articles composed of titanium or titanium alloys, comprising contacting the article composed of titanium or titanium alloys with a preparation containing 200 to 400 g/l NaOH and 10 to 150 g/l MGDA in water, wherein the content of further substances is less than 1 g/l and the pH of the preparation has a pH of at least 12, preferably at least 13, for 5 to 60 minutes at 20 to 80° C.
- Contacting can in this case be immersion, spraying, coating. The process according to the invention makes it possible to produce nanostructures having dimensions of below 100 nm, and hence to produce a mechanical and chemical anchoring by means of an enlarged surface area, which improves the durability and adhesion properties of titanium or titanium alloys thus treated.
- It is preferable here if in the preparation according to the invention the fluoride content is not detectable or is less than 0.001% by weight, based on the fluoride present in the preparation used. It is further preferable if the content of NaOH is 300 to 375 g/l, preferably 350 g/l, and the content of MGDA is 30 to 100 g/l, preferably 60 g/l. It is further preferable if the preparation according to the invention has a content of polymeric thickeners. It is preferable here if the thickeners used are xanthan gum or agar-agar and/or the thickener is present in concentrations of 2 to 40 g/l, preferably 10 to 15 g/l. It is further preferable if the content of further substances in the preparation according to the invention is less than 0.5 g/l, preferably 0.3 g/l. It is further preferable if the contacting is effected by immersion. It is further preferable if the contacting is effected for 10 to 30 minutes at 40 to 70° C. It is further preferable if the contacting is effected for 20 minutes at 60° C.
- The process according to the invention particularly preferably comprises a pretreatment for ensuring the wettability of the titanium or titanium alloys, in particular, with surface-active substances. The process according to the invention further preferably comprises an aftertreatment for washing off the preparation according to the invention, in particular, by washing off with demineralized water.
- A product according to the present invention is an article composed of titanium or titanium alloys obtainable by a process according to the invention or using a preparation according to the invention. It is preferable if the article according to the invention composed of titanium or titanium alloys having a porous layer at the surface, wherein the pores are predominantly open, have a number-average pore size of less than 100 nm, preferably 30 to 70 nm.
- The invention further comprises an aircraft, in particular, an aircraft comprising an article according to the invention composed of titanium or titanium alloys.
- The above-described aspects and further aspects, features and advantages of the invention can also be gathered from the examples of embodiments which are described below with reference to the appended drawings.
- The examples show various treatments of various titanium alloys. The conditions are stated in each case. Prior to the treatment, the material samples are washed with isopropanol or with an alkaline degreasing agent (Metaclean T2001, experiments 7 and 8 only). After drying, the samples were treated with the aqueous solutions specified by immersion without movement or stirring. The solutions had a pH of approx. 14. After the treatment, the surface obtained was assessed visually. An iridescent surface indicates a surface modification with characteristic dimensions in the region of the wavelength of light (nanostructured surface).
-
NaOH MGDA T T # [g/l] [g/l] [° C.] [min] Evaluation/observation 1 Ti6Al4V 240 30 60 15 ++ green/blue iridescent surface 2 Ti6Al4V 240 60 60 15 ++ iridescent surface 3 Ti6Al4V 350 120 75 15 ++ iridescent surface 4 Ti6Al4V 350 — 65 15 − surface not nanostructured 5 Ti6Al4V 350 30 65 15 ++ iridescent surface 6 Ti6Al4V 450 30 65 15 + yellowish iridescent surface with violet specks 7 Ti6Al4V 200 30 65 15 ++ green/blue iridescent surface 8 Cp-Ti 200 30 65 15 ++ violet/blue iridescent surface 9 Ti6Al4V 350 60 60 15 ++ iridescent surface - A loss of mass was observed in experiment 5 only.
- SEM images of the surface obtained in experiment 5 show a sponge-like surface structure with pore sizes of 30 to 100 nm. The pore walls are of an open and irregularly network-like configuration.
- The roller peel test in accordance with DIN 2243-2 showed exceptional adhesion compared to untreated titanium sheet: at room temperature there was exclusively failure of the adhesive layer and not detachment of the bond, and at −55° C. there was 95% failure of the bond. (Surface pretreatment by alkaline cleaning followed by treatment with HNO3/HF mixture, then analogous to example 5, Ti peel plate: 300*210*0.4 mm, BR 127 primer (cytec), FM 94 adhesive (cytec); room temperature: 174.9 N (100% cohesive failure); −55° C.: 141.2 N (95% cohesive failure)).
- It is noted that the embodiments described are merely illustrative and are not restrictive.
- While the invention has been illustrated and described in detail in the examples and the preceding description, it is intended that such illustrations and descriptions be merely illustrative or exemplary and not restrictive, so that the invention is not limited by the embodiments disclosed. In the claims, the word “having” does not exclude other elements and the indefinite article “a” does not exclude a plurality.
- The mere fact of mentioning certain features in various dependent claims does not restrict the subject matter of the invention. Combinations of these features can also be used to advantage.
- While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.
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DE102018005156.1A DE102018005156A1 (en) | 2018-06-29 | 2018-06-29 | Preparation for surface pretreatment by chemical conversion of the oxide layers of titanium or titanium alloys |
PCT/EP2019/067602 WO2020002706A2 (en) | 2018-06-29 | 2019-07-01 | Preparation for pre-treating surfaces by chemically converting oxide layers of titanium or titanium alloys |
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US10221347B2 (en) * | 2014-12-03 | 2019-03-05 | Halliburton Energy Services, Inc. | Methods and systems for suppressing corrosion of sensitive metal surfaces |
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DE202019101351U1 (en) * | 2018-04-27 | 2019-03-29 | Dr. Schumacher Gmbh | Cleaning system for surgical instruments |
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2018
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