EP3967791A1 - Enhanced corrosion resistance process for bulk metallic glass substrates - Google Patents
Enhanced corrosion resistance process for bulk metallic glass substrates Download PDFInfo
- Publication number
- EP3967791A1 EP3967791A1 EP20196233.9A EP20196233A EP3967791A1 EP 3967791 A1 EP3967791 A1 EP 3967791A1 EP 20196233 A EP20196233 A EP 20196233A EP 3967791 A1 EP3967791 A1 EP 3967791A1
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- European Patent Office
- Prior art keywords
- metal
- bmg
- based glass
- glass substrate
- process according
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- 239000000758 substrate Substances 0.000 title claims abstract description 110
- 238000005260 corrosion Methods 0.000 title claims abstract description 36
- 230000007797 corrosion Effects 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000008569 process Effects 0.000 title claims abstract description 33
- 239000005300 metallic glass Substances 0.000 title description 5
- 238000011282 treatment Methods 0.000 claims abstract description 30
- 229910052751 metal Inorganic materials 0.000 claims abstract description 29
- 239000002184 metal Substances 0.000 claims abstract description 29
- 239000011521 glass Substances 0.000 claims abstract description 23
- 239000010936 titanium Substances 0.000 claims abstract description 22
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 21
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 15
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 15
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000004411 aluminium Substances 0.000 claims abstract description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 8
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 5
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052737 gold Inorganic materials 0.000 claims abstract description 5
- 239000010931 gold Substances 0.000 claims abstract description 5
- 229910052735 hafnium Inorganic materials 0.000 claims abstract description 5
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 5
- 239000011777 magnesium Substances 0.000 claims abstract description 5
- 230000002708 enhancing effect Effects 0.000 claims abstract description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 14
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 13
- 229910045601 alloy Inorganic materials 0.000 claims description 13
- 239000000956 alloy Substances 0.000 claims description 13
- 239000008367 deionised water Substances 0.000 claims description 13
- 229910021641 deionized water Inorganic materials 0.000 claims description 13
- 239000007864 aqueous solution Substances 0.000 claims description 10
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- 238000005238 degreasing Methods 0.000 claims description 7
- 238000005498 polishing Methods 0.000 claims description 7
- 238000002203 pretreatment Methods 0.000 claims description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 235000006408 oxalic acid Nutrition 0.000 claims description 4
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 4
- 239000008139 complexing agent Substances 0.000 claims description 3
- 239000010985 leather Substances 0.000 claims description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims 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 claims description 2
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 2
- 230000001680 brushing effect Effects 0.000 claims description 2
- 238000005488 sandblasting Methods 0.000 claims description 2
- 238000010186 staining Methods 0.000 claims description 2
- 238000012360 testing method Methods 0.000 description 25
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 18
- 239000010949 copper Substances 0.000 description 18
- 239000000243 solution Substances 0.000 description 18
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 17
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 17
- 238000002161 passivation Methods 0.000 description 15
- 239000010410 layer Substances 0.000 description 11
- 238000012544 monitoring process Methods 0.000 description 11
- 229910052802 copper Inorganic materials 0.000 description 10
- 238000004090 dissolution Methods 0.000 description 10
- 239000011780 sodium chloride Substances 0.000 description 9
- 238000006388 chemical passivation reaction Methods 0.000 description 8
- 229910052759 nickel Inorganic materials 0.000 description 7
- 230000004044 response Effects 0.000 description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 6
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 6
- 230000032683 aging Effects 0.000 description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 6
- 238000002048 anodisation reaction Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 230000007547 defect Effects 0.000 description 6
- 210000004243 sweat Anatomy 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- 238000005266 casting Methods 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 150000004820 halides Chemical class 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
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- 238000001453 impedance spectrum Methods 0.000 description 3
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- 239000007848 Bronsted acid Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000003929 acidic solution Substances 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
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- 238000004381 surface treatment Methods 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 1
- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 229910007932 ZrCl4 Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000007743 anodising Methods 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229940075397 calomel Drugs 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- OXBLHERUFWYNTN-UHFFFAOYSA-M copper(I) chloride Chemical compound [Cu]Cl OXBLHERUFWYNTN-UHFFFAOYSA-M 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical compound Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
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- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
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- 239000007800 oxidant agent Substances 0.000 description 1
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- 238000007712 rapid solidification Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
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- 238000005549 size reduction Methods 0.000 description 1
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- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- 230000003746 surface roughness Effects 0.000 description 1
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- 238000010408 sweeping Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 229910021642 ultra pure water Inorganic materials 0.000 description 1
- 239000012498 ultrapure water Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/26—Anodisation of refractory metals or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/186—High-melting or refractory metals or alloys based thereon of zirconium or alloys based thereon
Definitions
- the invention relates to a surface treatment improving the resistance to corrosion of a metal-based glass (or bulk metallic glass) substrate. It involves an electrochemical anodic treatment, and eventually a chemical treatment, of the BMG substrate.
- BMG Bulk-metallic-glasses
- Some BMG can exhibit improved mechanical properties as compared to crystalline metals or crystalline alloys, such as large elastic strains to failure, high tensile strength, high hardness, high fatigue limit and high corrosion resistance.
- the amorphous properties of the BMG result from their manufacturing. Since they are made by rapid solidification from a melted phase (gas or liquid), the atoms are essentially blocked in a disordered matrix. Due to this fast solidification process, the resulting material, i.e. the BMG, has an amorphous structure rather than a periodic and well-defined crystalline structure.
- BMG Glass formability
- Some BMG have a critical casting thickness of several millimetres, which widens the scope of applications.
- zirconium based BMG such as the commercially available Vit105 (Zr 52.5 CU 17.9 Ni 14.6 Al 10 Ti 5 , at%) and Vit106a (Zr 58.5 Nb 2.8 Al 10.3 Ni 12.8 Cu 15.6 , at%) have a critical casting thickness of 18 and 32 mm, respectively. Such a difference may be due to the larger Cu/Zr ratio in Vit105.
- BMG can be used in many fields, for instance in the fields of fashion and luxury (watches, jewellery).
- BMG are amorphous alloys having the following features:
- BMG alloys include their resistance to general corrosion. However, the presence of halides in solution may significantly alter their corrosion resistance and give rise to pitting phenomena: this can be particularly observed in zirconium-based BMG.
- the resistance to corrosion of BMG substrates can be affected by:
- BMG alloys exhibit many advantageous properties, they may still suffer from pitting corrosion in the presence of oxidizing agents and halides / depassivating agents, such as chloride, bromide, fluoride and others. It can be significantly improved if the amount of non-passivable metals and halide friendly metals is reduced or eliminated in favour of passivable elements. Examples of non-passivable elements are copper, nickel, iron and silver.
- the Applicant has find out that, when anodising Vit105, the selective dissolution of non-passivable elements and the simultaneous surface enrichment of ZrO 2 , TiO 2 and Al 2 O 3 occur and lead to an enhancement of the pitting-corrosion resistance.
- the Applicant has developed a process that allows improving the resistance of BMG alloys to corrosion (general and pitting corrosion). This process involves an electrochemical anodisation and is applicable to all sorts of BMG alloys, even those having non-passivable elements.
- the Applicant has developed a process for improving the resistance to corrosion of BMG alloys thanks to specific passivation conditions.
- the invention involves the selective extraction of non-passivable elements such as copper or nickel from the external portion of the matrix i.e. from the surface of the treated substrate. Consequently, the outmost substrate layer has a composition enriched in passivable elements, such as zirconium, titanium or aluminium, which significantly differs from the bulk alloy composition and confers to the BMG an enhanced resistance to corrosion, particularly to pitting corrosion.
- the invention relates to a process for enhancing corrosion resistance of a metal-based glass (BMG) substrate, wherein the metal of the metal-based glass is any one of zirconium, titanium, hafnium, aluminium, magnesium, gold or a mixture thereof, and wherein the process comprises a step of exposing the substrate to an electrochemical anodic treatment applying a current density of from 0.2 mA.cm -2 to 500 mA.cm -2 .
- BMG metal-based glass
- the BMG substrate has a smooth surface. It has a surface roughness Ra of preferably less than 1 ⁇ m, more preferably less than 0.2 ⁇ m.
- a surface finishing treatment may be carried out on the BMG substrate prior to the electrochemical anodic treatment (EAT).
- the process may comprise a step of surface finishing, such as at least one of polishing, brushing, staining and sandblasting polishing, the metal-based glass substrate prior to the electrochemical anodic treatment.
- This optional surface finishing step may be carried out with any abrasive, for instance with abrasive paper grade 800, followed by grades 2000 and 4000, and final polishing with alumina suspension.
- the BMG substrate may be degreased. Any conventional degreasing mean may be used, for instance an alcohol such as isopropanol.
- Degreasing the BMG is preferably completed at room temperature, for instance at a temperature of between 16 and 30°C.
- the BMG substrate Prior to the EAT, and preferably after each of the surface finishing step and degreasing steps, the BMG substrate may be rinsed with deionized water. Rinsing is preferably carried out at room temperature, for instance at a temperature of between 16 and 30°C.
- the pre-treatment may include a chemical passivation step of the BMG substrate, preferably in an acidic solution (Br ⁇ nsted acid), for instance in an aqueous solution having a pH of less than 7.
- an acidic solution Ba ⁇ nsted acid
- the acidic solution is preferably an aqueous solution comprising one or more of the following acids: nitric acid, sulfuric acid, oxalic acid, and citric acid, preferably citric acid.
- the acid (Br ⁇ nsted acid) concentration of the passivation solution preferably ranges from 10 -3 M to 2 M (mol.L -1 ).
- the chemical passivation is preferably performed at a temperature of from 5°C to 60°C, more preferably from 20°C to 40°C, for instance at 25°C.
- the duration of the chemical passivation is not crucial since contacting the BMG substrate with the passivation solution can be as short as a few seconds, for instance from 1 second to 5 minutes.
- the BMG substrates can be rinsed, preferably with deionized water. It can also be dried prior to the EAT.
- This chemical passivation allows concentrating passivating elements at the surface of the BMG substrate.
- the pre-treatment may include the following sequence:
- the electrochemical anodic treatment involves exposing the BMG substrate to a 0.5 mA.cm -2 to 1000 mA.cm -2 current density, preferably 10 to 500 mA cm -2 , more preferably 50 to 300 mA.cm -2 .
- This specific treatment enhances the resistance to corrosion of the BMG substrate while conventional anodisation treatments, when performed at higher current densities, lead to the dissolution of the BMG surface layer, thus altering the shape and the aesthetic of the specimen.
- This phenomenon may be due to the presence of non-passivable elements, for instance any one of Cu, Co, Ni or Fe.
- non-passivable elements are present in BMG since they bring in mechanical properties and improve the critical casting thickness of the alloys.
- non-passivable elements are responsible of the BMG surface dissolution in conventional anodisation conditions.
- the Applicant has surprisingly found out that applying mild current densities leads to the selective dissolution of non-passivable elements and to the formation of a stable metal oxide layer.
- the resulting passivation layer is enriched in passivation elements.
- Passivation elements include, for instance, one or more of zirconium, titanium and aluminium.
- Figure 3 clearly shows i) how the BMG surface composition changes when the process of the invention is applied, and ii) the formation of a passivation layer (dashed line).
- Figure 3 illustrates this phenomenon for a BMG substrate such as Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (at%). In fact, it shows that an equilibrium is attainted with i) the enrichment of the surface layer in Zr, Ti and Al and ii) the selective dissolution of Cu and Ni. This is due to the specific conditions of the invention.
- the thickness of the treated substrate decreases.
- a current densities ranging between 10 and 500 mA cm -2 is applied for 60 seconds on a Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (at%) substrate, a size reduction of approximately 1 to 1.5 micrometers is observed, preserving the aesthetic of the substrate.
- the dissolution rate overcomes the passivation rate, and the sample simply physically degrades.
- the invention preserves the aesthetic of the BMG substrate including its visual aspect, such as its colour.
- BMG substrates do not behave like Ti, Zr or Al substrates, for which, upon applying a high current density, an oxide layer with a thickness ranging from a couple of nanometers to several hundred nanometers, is readily formed and physically protects the underneath Ti, Zr or Al metal.
- the above 0.5-1000 mA.cm -2 current density is applied for a duration that preferably ranges from 5 seconds to 300 seconds, more preferably 30 to 90 seconds.
- the EAT is generally carried out in an electrolyte bath, preferably in an aqueous solution.
- the electrolyte bath may be acidic, neutral or alkaline, preferably acidic (pH ⁇ 7), more preferably at a pH of between 0 and 6.
- the electrolyte bath is preferably an acidic aqueous solution comprising one or more acid selected from the group consisting of sulfuric acid, phosphoric acid, oxalic acid, citric acid, perchloric acid and nitric acid. It is preferably an aqueous solution of a mixture of sulfuric acid and phosphoric acid.
- the electrolyte bath can have a concentration in acid preferably ranging from 10 -4 M to 10 M, preferentially from 10 -3 M to 2 M.
- the EAT is preferably carried out at a temperature preferably ranging from 5°C to 60°C, more preferably from 20°C to 40°C. For instance, it may be carried out at 40°C for 60 seconds.
- the EAT may be carried out in a solution, preferably an aqueous solution, comprising one or more complexing agent selected from the group consisting of ethylenediaminetetraacetic acid, citrate, ethylenediamine, and oxalate.
- a solution preferably an aqueous solution, comprising one or more complexing agent selected from the group consisting of ethylenediaminetetraacetic acid, citrate, ethylenediamine, and oxalate.
- the complexing agent can have a concentration preferably ranging from 10 -4 M to 1 M.
- the BMG substrate is an amorphous metal-based glass (BMG) substrate, wherein the metal is one or more of zirconium, titanium, hafnium, aluminium, magnesium and gold.
- BMG amorphous metal-based glass
- the BMG substrate is preferably a zirconium based BMG. In other words, it is preferably an alloy whose main element (largest atomic percentage) is zirconium.
- Examples of preferred BMG include Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (at%), Zr 58.5 Cu 15.6 Ni 12.8 Al 10.3 Nb 2.8 .
- the EAT is followed by a chemical passivation of the BMG substrate.
- a chemical passivation of the BMG substrate may differ from the early chemical passivation of the pre-treatment, the general conditions of this late chemical passivation are identical (passivation solution, temperature and duration).
- the BMG substrate can be rinsed, preferably with deionized water. It may also be dried. Any conventional drying may be carried out, for instance by blowing hot air on the substrate or in an oven, preferably at a temperature of between 30 and 50 °C.
- the post-treatment may therefore include the following sequence:
- the invention also relates to a luxury component or good (horology, jewellery, leather goods, writing accessories, ornaments and fashion) comprising the BMG substrate treated according to the present invention.
- the fields of use of the BMG substrate treated according to the present invention include horology (watch case, dial, watch strap, watch clasp, mechanical part of a watch movement%), jewellery (ring, earring, necklace, bracelet, pendant, etc.), leather goods (belt buckles, handbag clasps%), writing accessories (pens, paper cutters%), ornaments and fashion accessories (cuff links, tie pin, money clip, hairpin, hair clip).
- Zr-based BMG substrates (Vit105, Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 - 15 mm x 15 mm and thickness of 2 mm) have been treated according to the invention:
- the resulting BMG substrates have been compared to the non-treated BMG substrate i.e. the substrate before step 2.
- the treatment according to the invention has been carried out in an electrochemical cell having a three electrode configuration: working electrode (BMG), auxiliary electrode (large Pt sheet) and a KCl saturated reference calomel electrode (SCE).
- BMG working electrode
- auxiliary electrode large Pt sheet
- SCE KCl saturated reference calomel electrode
- Electrochemical tests were carried out at 23 ⁇ 1°C. Unless otherwise stated, all the potential values are referred to SCE. Electrochemical tests, such as EIS measurements (EIS: electrochemical impedance spectroscopy), were carried out in potentiostat such as the Gamry Reference 600.
- PP Potentiodynamic polarization
- EIS electrochemical impedance spectroscopy
- PP were performed sweeping the potential from cathodic (-0.2 V vs. OCP) to anodic values at a scan rate of 0.15 mV/s and step potential of 0.15 mV.
- the used solution for both PP and EIS was an artificial sweat EN1811, made with ultrapure water (conductivity of 18.2 MQ.cm).
- EIS tests was carried out applying an alternate potential of 5 mV at OCP within a frequency range from 100000 Hz and 0.005 Hz with ten points per decade.
- the electrode surface was either 0.50 cm 2 or 0.12 cm 2 .
- Electrochemical monitoring was carried out by exposing (anodically treated or not) Zr-BMG substrates to a 3 M NaCl solution at pH 3 ( figures 4 and 8 ).
- the monitoring consisted of OCP measurements alternated with EIS measurements.
- EIS were measured after 1 hr, 4 hr, 9 hr, 24 hr, 43 hr and 67 hr and were carried out applying an alternate potential of 5 mV at OCP within a frequency ranging from 100000 Hz to 0.005 Hz, with ten points per decade.
- the aged BMG substrates were rinsed with water and corrosion inspected, using an optical microscope ( figures 5, 6 and 7 ).
- At least 10 samples per each surface treatment were considered for statistical analysis.
- Figure 1 shows an overlay of potentiodynamic polarisations carried out in artificial sweat (EN1811) at 0.15 mV/s on the following BMG substrates:
- the original BMG is the same for all experiments, 1 ⁇ m polished Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 .
- the corrosion current density for the invention substrate was determined significantly lower than that of the other BMG substrates.
- the determined values were in fact 1 nA.cm -2 and 18 nA.cm -2 , for the invention and the non-treated substrate, respectively.
- the resistance to pitting corrosion of BMG substrates, in particular Zr-based BMG significantly decreases in the presence of chloride ions or other depassivating agent in the electrolyte (0.085 M NaCl in the EN1811 solution of the PP and EIS tests).
- Figure 1 shows that localized corrosion is initiated at 0.180 V for the non-treated BMG substrate while potential values up to 1.0 V are attainable for the BMG according to the invention.
- Figure 2 shows the EIS Nyquist plot of the BMG substrate according to the invention and the non-treated BMG substrate, in artificial sweat EN1811 with a potential amplitude of 5 mV, within a frequency range from 100000 Hz and 0.005 Hz.
- the BMG substrate treated according to the invention shows a higher impedance response than the non-treated BMG substrate. It actually shows a nearly vertical trend, which is typical of capacitive response and therefore of the presence of a thin passive layer.
- the non-treated substrate exhibits a lower impedance and therefore no protective layer or at least a thinner protective layer than that of the BMG substrate according to the invention.
- the higher capacitive response of the anodically treated BMG substrate can be explained in terms of Cu and Ni dissolution from the outmost electrode surface, and its simultaneous enrichment of Zr, Al and Ti elements, present as oxides. From Figure 2 inset it can be appreciated the higher impedance modulus values for the treated sample, and as well as the attainment of a phase angle of 90° at low frequencies, typical of a capacitive behaviour.
- reaction mechanisms that is, i) enrichment of Zr, Ti and Al and ii) selective dissolution of Cu and Ni, attain an equilibrium as depicted in Figure 3 .
- the dissolution rate overcomes the passivation rate, and the sample simply physically degrades.
- Electrochemical monitoring tests were also carried out to assess how the treated samples endured long-lasting aggressive solutions (3M NaCl, pH 3) compared to non-treated samples.
- Figure 4 shows the EIS response (Nyquist plot) carried out over 42 hours of monitoring on a non-treated substrate.
- the low hand-side Figure 4 inset highlights the OCP, recorded in between the EIS, whereas the top hand-side Figure 4 shows a magnification of the recorded EIS.
- the stability of the non-treated BMG substrate significantly decreases between 15 and 25 hours, the impedance response changing from a capacitive to a kinetic transfer controlled behaviour (see the top hand side inset of figure 4 ).
- FIG. 5 An optical microscope image of the BMG sample surface after monitoring testing for 42 hours is shown in Figure 5 .
- the sample in addition to be completely whitish on the external surface (signs of formation of insoluble chlorides, ZrCl 4 and CuCl) also exhibited two deep greenish-brownish pits, enriched in copper (ca. 70 at. %) and depleted in Zr and other alloying elements.
- This dissolution mechanism corresponds to pitting corrosion in chloride solutions of Zr, Al and Ti with the simultaneous accumulation of copper.
- the scanning-electron microscope image of the pits ( Figure 6 ) shows the corrosion pits after 42 hours of sample exposure to the solution.
- EIS monitoring tests carried out on the BMG substrate, treated according to the invention shows a rather stable capacitive response during a monitoring time of 72 hours ( Figure 8 ).
- the substrate does not show any visible signs of corrosion after testing.
- Figure 7 shows the absence of whitish surface portions and of greenish-brownish pits.
- the impedance response recorded over the time interval was observed to be rather stable and to have a capacitive behaviour up to 67 hours.
- the recorded OCP starts at values of approximately -0.15 V, decreases down to approximately -0.25 V and then steadily increases attaining values of -0.10 V (inset of Figure 8 ). No OCP scattering (common sign chemical instability) was observed on treated samples.
Abstract
Description
- The invention relates to a surface treatment improving the resistance to corrosion of a metal-based glass (or bulk metallic glass) substrate. It involves an electrochemical anodic treatment, and eventually a chemical treatment, of the BMG substrate.
- Bulk-metallic-glasses (BMG) are metallic alloys having an amorphous structure. Some BMG can exhibit improved mechanical properties as compared to crystalline metals or crystalline alloys, such as large elastic strains to failure, high tensile strength, high hardness, high fatigue limit and high corrosion resistance.
- The amorphous properties of the BMG result from their manufacturing. Since they are made by rapid solidification from a melted phase (gas or liquid), the atoms are essentially blocked in a disordered matrix. Due to this fast solidification process, the resulting material, i.e. the BMG, has an amorphous structure rather than a periodic and well-defined crystalline structure.
- Another important feature of BMG is their glass formability. It relates to the ability of casting a sample free of crystals or nanocrystals. It is also described as the critical casting thickness of BMG, which is the maximum thickness of amorphous material that can be attained.
- Some BMG have a critical casting thickness of several millimetres, which widens the scope of applications. For instance, zirconium based BMG such as the commercially available Vit105 (Zr52.5CU17.9Ni14.6Al10Ti5, at%) and Vit106a (Zr58.5Nb2.8Al10.3Ni12.8Cu15.6, at%) have a critical casting thickness of 18 and 32 mm, respectively. Such a difference may be due to the larger Cu/Zr ratio in Vit105.
- In view of the above properties, BMG can be used in many fields, for instance in the fields of fashion and luxury (watches, jewellery...).
- Typically, BMG are amorphous alloys having the following features:
- multicomponent system,
- the constituting elements have atomic size ratios exceeding 1.12,
- most of the alloying elements have a large and negative mixing enthalpy.
- Other important properties of BMG alloys include their resistance to general corrosion. However, the presence of halides in solution may significantly alter their corrosion resistance and give rise to pitting phenomena: this can be particularly observed in zirconium-based BMG.
- The resistance to corrosion of BMG substrates can be affected by:
- The presence of defects at the surface of the BMG. For instance, nanocrystals or mechanically generated defects can promote the initiation of local corrosion and its propagation within the BMG, that is, formation of pits and crevices.
- The surface finishing of the BMG. Evidences of this have been given by Gebert et al. [A. Gebert, P. Gostin and L. Schultz, "Effect of surface finishing of a Zr-based bulk metallic glass on its corrosion behaviour," Corr. Sci., vol. 52, pp. 1711-1720, 2010], where a fine surface polishing of Zr-based BMGs (0.02 µm SiO2 abrasive solution) resulted in a copper enrichment of the outmost surface with low resistance to pitting corrosion, whereas a rougher polishing (4000 SiC paper) led to a zirconium and aluminium oxides enriched surface, with an improved corrosion resistance.
- The chemical composition of the passivation layer of the BMG.
- The presence of halides and/or oxidising compounds.
- The presence of local composition-inhomogeneity, originated from a not optimised manufacturing process.
- Although BMG alloys exhibit many advantageous properties, they may still suffer from pitting corrosion in the presence of oxidizing agents and halides / depassivating agents, such as chloride, bromide, fluoride and others. It can be significantly improved if the amount of non-passivable metals and halide friendly metals is reduced or eliminated in favour of passivable elements. Examples of non-passivable elements are copper, nickel, iron and silver.
- In order to improve the resistance to corrosion of BMG alloy, such as Vit105, passivation treatments have been tested. Such treatments are commonly, and successfully, used for improving the resistance to corrosion of aluminium, titanium or stainless steel substrates. However, when carrying out conventional anodisation on Vit105, the formation of a typical passivation layer is not usually achieved.
- Indeed, when passivating titanium or zirconium, the current density significantly decreases during the process, due to the formation of thick and insulating TiO2 and ZrO2 layers. Conversely, on Vit105 this particular current density decrease is not observed due to the low content of passivation elements (Zr, Ti and Al) and, certainly, to the significant content of non-passivable elements (Cu and Ni), within the oxide layer of ZrO2, TiO2 and Al2O3 and, that weaken its whole stability. As a result, the skilled person in the art could not find any motivation to apply such an anodisation treatment on a BMG alloy in order to form a passivation layer.
- However, despite this, the Applicant has find out that, when anodising Vit105, the selective dissolution of non-passivable elements and the simultaneous surface enrichment of ZrO2, TiO2 and Al2O3 occur and lead to an enhancement of the pitting-corrosion resistance.
- The Applicant has developed a process that allows improving the resistance of BMG alloys to corrosion (general and pitting corrosion). This process involves an electrochemical anodisation and is applicable to all sorts of BMG alloys, even those having non-passivable elements.
- The Applicant has developed a process for improving the resistance to corrosion of BMG alloys thanks to specific passivation conditions.
- Unlike traditional anodisation processes, the invention involves the selective extraction of non-passivable elements such as copper or nickel from the external portion of the matrix i.e. from the surface of the treated substrate. Consequently, the outmost substrate layer has a composition enriched in passivable elements, such as zirconium, titanium or aluminium, which significantly differs from the bulk alloy composition and confers to the BMG an enhanced resistance to corrosion, particularly to pitting corrosion.
- More specifically, the invention relates to a process for enhancing corrosion resistance of a metal-based glass (BMG) substrate, wherein the metal of the metal-based glass is any one of zirconium, titanium, hafnium, aluminium, magnesium, gold or a mixture thereof, and wherein the process comprises a step of exposing the substrate to an electrochemical anodic treatment applying a current density of from 0.2 mA.cm-2 to 500 mA.cm-2.
- These conditions allow the above mentioned selective extraction of non-passivable elements and also preserve the aesthetic of the substrate. It can therefore be applied on a substrate after a surface finishing treatment, for instance on a substrate (preferably a luxury component or luxury goods) that is ready to be commercialized.
- According to a preferred embodiment, the BMG substrate has a smooth surface. It has a surface roughness Ra of preferably less than 1 µm, more preferably less than 0.2 µm.
- As a result, a surface finishing treatment may be carried out on the BMG substrate prior to the electrochemical anodic treatment (EAT). The process may comprise a step of surface finishing, such as at least one of polishing, brushing, staining and sandblasting polishing, the metal-based glass substrate prior to the electrochemical anodic treatment.
- This optional surface finishing step may be carried out with any abrasive, for instance with abrasive paper grade 800, followed by
grades - Prior to the EAT, but after the optional surface finishing step, the BMG substrate may be degreased. Any conventional degreasing mean may be used, for instance an alcohol such as isopropanol.
- Degreasing the BMG is preferably completed at room temperature, for instance at a temperature of between 16 and 30°C.
- Prior to the EAT, and preferably after each of the surface finishing step and degreasing steps, the BMG substrate may be rinsed with deionized water. Rinsing is preferably carried out at room temperature, for instance at a temperature of between 16 and 30°C.
- The pre-treatment may include a chemical passivation step of the BMG substrate, preferably in an acidic solution (Brønsted acid), for instance in an aqueous solution having a pH of less than 7.
- The acidic solution is preferably an aqueous solution comprising one or more of the following acids: nitric acid, sulfuric acid, oxalic acid, and citric acid, preferably citric acid.
- The acid (Brønsted acid) concentration of the passivation solution preferably ranges from 10-3 M to 2 M (mol.L-1).
- The chemical passivation is preferably performed at a temperature of from 5°C to 60°C, more preferably from 20°C to 40°C, for instance at 25°C.
- The duration of the chemical passivation is not crucial since contacting the BMG substrate with the passivation solution can be as short as a few seconds, for instance from 1 second to 5 minutes.
- After the chemical passivation, the BMG substrates can be rinsed, preferably with deionized water. It can also be dried prior to the EAT.
- This chemical passivation allows concentrating passivating elements at the surface of the BMG substrate.
- Accordingly, the pre-treatment may include the following sequence:
- a) optionally, surface finishing the BMG substrate,
- b) optionally rinsing the BMG substrate with deionized water,
- c) optionally degreasing the BMG substrate,
- d) optionally rinsing the BMG substrate with deionized water,
- e) optionally, passivating the BMG substrate,
- f) optionally rinsing the BMG substrate with deionized water,
- e) optionally, drying the BMG substrate.
- The electrochemical anodic treatment involves exposing the BMG substrate to a 0.5 mA.cm-2 to 1000 mA.cm-2 current density, preferably 10 to 500 mA cm-2, more preferably 50 to 300 mA.cm-2.
- This specific treatment enhances the resistance to corrosion of the BMG substrate while conventional anodisation treatments, when performed at higher current densities, lead to the dissolution of the BMG surface layer, thus altering the shape and the aesthetic of the specimen. This phenomenon may be due to the presence of non-passivable elements, for instance any one of Cu, Co, Ni or Fe. Such non-passivable elements are present in BMG since they bring in mechanical properties and improve the critical casting thickness of the alloys.
- These non-passivable elements are responsible of the BMG surface dissolution in conventional anodisation conditions. However, the Applicant has surprisingly found out that applying mild current densities leads to the selective dissolution of non-passivable elements and to the formation of a stable metal oxide layer. The resulting passivation layer is enriched in passivation elements. Passivation elements include, for instance, one or more of zirconium, titanium and aluminium.
Figure 3 clearly shows i) how the BMG surface composition changes when the process of the invention is applied, and ii) the formation of a passivation layer (dashed line). -
Figure 3 illustrates this phenomenon for a BMG substrate such as Zr52.5Cu17.9Ni14.6Al10Ti5 (at%). In fact, it shows that an equilibrium is attainted with i) the enrichment of the surface layer in Zr, Ti and Al and ii) the selective dissolution of Cu and Ni. This is due to the specific conditions of the invention. - Due to the loss of non-passivable elements, the thickness of the treated substrate decreases. In general, if a current densities ranging between 10 and 500 mA cm-2 is applied for 60 seconds on a Zr52.5Cu17.9Ni14.6Al10Ti5 (at%) substrate, a size reduction of approximately 1 to 1.5 micrometers is observed, preserving the aesthetic of the substrate. On the other hand, if the current density is too important, the dissolution rate overcomes the passivation rate, and the sample simply physically degrades. As already mentioned, the invention preserves the aesthetic of the BMG substrate including its visual aspect, such as its colour.
- Due to the presence of non passivable elements, BMG substrates do not behave like Ti, Zr or Al substrates, for which, upon applying a high current density, an oxide layer with a thickness ranging from a couple of nanometers to several hundred nanometers, is readily formed and physically protects the underneath Ti, Zr or Al metal.
- The above 0.5-1000 mA.cm-2 current density is applied for a duration that preferably ranges from 5 seconds to 300 seconds, more preferably 30 to 90 seconds.
- The EAT is generally carried out in an electrolyte bath, preferably in an aqueous solution.
- The electrolyte bath may be acidic, neutral or alkaline, preferably acidic (pH < 7), more preferably at a pH of between 0 and 6.
- The electrolyte bath is preferably an acidic aqueous solution comprising one or more acid selected from the group consisting of sulfuric acid, phosphoric acid, oxalic acid, citric acid, perchloric acid and nitric acid. It is preferably an aqueous solution of a mixture of sulfuric acid and phosphoric acid.
- The electrolyte bath can have a concentration in acid preferably ranging from 10-4 M to 10 M, preferentially from 10-3 M to 2 M.
- The EAT is preferably carried out at a temperature preferably ranging from 5°C to 60°C, more preferably from 20°C to 40°C. For instance, it may be carried out at 40°C for 60 seconds.
- The EAT may be carried out in a solution, preferably an aqueous solution, comprising one or more complexing agent selected from the group consisting of ethylenediaminetetraacetic acid, citrate, ethylenediamine, and oxalate.
- When present, the complexing agent can have a concentration preferably ranging from 10-4 M to 1 M.
- As already mentioned, the BMG substrate is an amorphous metal-based glass (BMG) substrate, wherein the metal is one or more of zirconium, titanium, hafnium, aluminium, magnesium and gold.
- The BMG substrate is preferably a zirconium based BMG. In other words, it is preferably an alloy whose main element (largest atomic percentage) is zirconium.
- Examples of preferred BMG include Zr52.5Cu17.9Ni14.6Al10Ti5 (at%), Zr58.5Cu15.6Ni12.8Al10.3Nb2.8.
- Optionally, the EAT is followed by a chemical passivation of the BMG substrate. Although it may differ from the early chemical passivation of the pre-treatment, the general conditions of this late chemical passivation are identical (passivation solution, temperature and duration).
- Thereafter the BMG substrate can be rinsed, preferably with deionized water. It may also be dried. Any conventional drying may be carried out, for instance by blowing hot air on the substrate or in an oven, preferably at a temperature of between 30 and 50 °C.
- The post-treatment may therefore include the following sequence:
- aa) optionally rinsing the BMG substrate, preferably with deionized water,
- bb) optionally, passivating the BMG substrate,
- cc) optionally rinsing the BMG substrate, preferably with deionized water,
- dd) optionally, drying the BMG substrate.
- The invention also relates to a luxury component or good (horology, jewellery, leather goods, writing accessories, ornaments and fashion) comprising the BMG substrate treated according to the present invention.
- The fields of use of the BMG substrate treated according to the present invention include horology (watch case, dial, watch strap, watch clasp, mechanical part of a watch movement...), jewellery (ring, earring, necklace, bracelet, pendant, etc.), leather goods (belt buckles, handbag clasps...), writing accessories (pens, paper cutters...), ornaments and fashion accessories (cuff links, tie pin, money clip, hairpin, hair clip...).
- The invention and its advantages will become more apparent to one skilled in the art from the following figures and examples.
-
-
Figure 1 shows potentiodynamic polarisation curves of BMG substrates that have been treated according to the invention or not. -
Figure 2 shows electrochemical impedance spectra of BMG substrates that have been treated according to the invention or not. The Inset shows the Bode plots (phase angle and modulus of the impedance) for these substrates. -
Figure 3 illustrates the enhanced corrosion resistance resulting from the process according to the invention. -
Figure 4 shows electrochemical impedance spectra of BMG substrates that have not been treated according to the invention, after ageing for 1 to 42 hours in a 3M NaCl solution atpH 3. -
Figure 5 is an optical microscope image of a non-treated BMG substrate, after EIS electrochemical monitoring test in a 3M NaCl solution atpH 3. -
Figure 6 is a SEM image of a non-treated BMG substrate, after EIS electrochemical monitoring test in a 3M NaCl solution atpH 3. -
Figure 7 is an optical microscope image of a BMG substrate treated according to the invention, after EIS electrochemical monitoring test in a 3M NaCl solution atpH 3. -
Figure 8 shows electrochemical impedance spectra of BMG substrates that have been treated according to the invention, after ageing for 1 to 67 hours in a 3M NaCl solution atpH 3. - Zr-based BMG substrates (Vit105, Zr52.5Cu17.9Ni14.6Al10Ti5 - 15 mm x 15 mm and thickness of 2 mm) have been treated according to the invention:
- 1) pre-treatment of the BMG substrates:
- surface finishing with
abrasive paper 800, 2500 and 4000 grades followed by 1 µm alumina dispersion slurry mirror-like finishing, - degreasing of the BMG substrate using isopropanol at room temperature (RT),
- rinsing the BMG substrate with deionized water,
- surface finishing with
- 2) anodic treatment of the BMG substrate in a 0.5 M H2SO4 + H3PO4 (70-30 % ratio - pH 0.2-0.3) electrolytic bath with a continuous current density of 100 mA cm-2 for 60 seconds and a temperature of 30° C,
- 3) rinsing the BMG substrate with deionized water.
- The resulting BMG substrates have been compared to the non-treated BMG substrate i.e. the substrate before step 2.
- The treatment according to the invention has been carried out in an electrochemical cell having a three electrode configuration: working electrode (BMG), auxiliary electrode (large Pt sheet) and a KCl saturated reference calomel electrode (SCE).
- Tests were carried out at 23 ± 1°C. Unless otherwise stated, all the potential values are referred to SCE. Electrochemical tests, such as EIS measurements (EIS: electrochemical impedance spectroscopy), were carried out in potentiostat such as the Gamry Reference 600.
- Potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) were carried out to characterize the electrochemical behavior. Prior testing, open circuit potential (OCP) was measured for 60 minutes to assess the stability of the BMG.
- PP were performed sweeping the potential from cathodic (-0.2 V vs. OCP) to anodic values at a scan rate of 0.15 mV/s and step potential of 0.15 mV. The used solution for both PP and EIS was an artificial sweat EN1811, made with ultrapure water (conductivity of 18.2 MQ.cm). EIS tests was carried out applying an alternate potential of 5 mV at OCP within a frequency range from 100000 Hz and 0.005 Hz with ten points per decade. The electrode surface was either 0.50 cm2 or 0.12 cm2.
- Electrochemical monitoring was carried out by exposing (anodically treated or not) Zr-BMG substrates to a 3 M NaCl solution at pH 3 (
figures 4 and8 ). The monitoring consisted of OCP measurements alternated with EIS measurements. - EIS were measured after 1 hr, 4 hr, 9 hr, 24 hr, 43 hr and 67 hr and were carried out applying an alternate potential of 5 mV at OCP within a frequency ranging from 100000 Hz to 0.005 Hz, with ten points per decade.
- Ageing tests were carried out on (anodically treated or not) Zr-BMG substrates. Zr-BMG substrates, produced with different shapes, were subjected to the following ageing tests:
- 1. Salt-fog-chamber test carried out by exposing the samples to a salt-fog environment (0.9 M NaCl) at 40° C for 4 days, according to the standard NIHS 96-50,
- 2. Thermal shock test carried out by submerging samples in water at 70° C for 30 minutes followed by submersion in water at 5° C for 5 minutes,
- 3. Moist-heat test carried out exposing the samples to a 95 % humid environment at 70° C for 7 days, according to the standard NIHS 96-50,
- 4. Artificial sweat test carried out exposing the samples to an artificial sweat solution at 40° C for 7 days, according to the standard NIHS 96-50.
- At the end of the series of tests, the aged BMG substrates were rinsed with water and corrosion inspected, using an optical microscope (
figures 5, 6 and7 ). - At least 10 samples per each surface treatment were considered for statistical analysis.
-
Figure 1 shows an overlay of potentiodynamic polarisations carried out in artificial sweat (EN1811) at 0.15 mV/s on the following BMG substrates: - BMG according to the invention ("invention" curve),
- non-treated BMG ("non-treated" curve).
- As already mentioned, the original BMG is the same for all experiments, 1 µm polished Zr52.5Cu17.9Ni14.6Al10Ti5.
- The corrosion current density for the invention substrate was determined significantly lower than that of the other BMG substrates. The determined values were in
fact 1 nA.cm-2 and 18 nA.cm-2, for the invention and the non-treated substrate, respectively. - As already mentioned, the resistance to pitting corrosion of BMG substrates, in particular Zr-based BMG, significantly decreases in the presence of chloride ions or other depassivating agent in the electrolyte (0.085 M NaCl in the EN1811 solution of the PP and EIS tests).
-
Figure 1 shows that localized corrosion is initiated at 0.180 V for the non-treated BMG substrate while potential values up to 1.0 V are attainable for the BMG according to the invention. -
Figure 2 shows the EIS Nyquist plot of the BMG substrate according to the invention and the non-treated BMG substrate, in artificial sweat EN1811 with a potential amplitude of 5 mV, within a frequency range from 100000 Hz and 0.005 Hz. - The BMG substrate treated according to the invention shows a higher impedance response than the non-treated BMG substrate. It actually shows a nearly vertical trend, which is typical of capacitive response and therefore of the presence of a thin passive layer. On the other hand, the non-treated substrate exhibits a lower impedance and therefore no protective layer or at least a thinner protective layer than that of the BMG substrate according to the invention.
- The higher capacitive response of the anodically treated BMG substrate can be explained in terms of Cu and Ni dissolution from the outmost electrode surface, and its simultaneous enrichment of Zr, Al and Ti elements, present as oxides. From
Figure 2 inset it can be appreciated the higher impedance modulus values for the treated sample, and as well as the attainment of a phase angle of 90° at low frequencies, typical of a capacitive behaviour. - The above mentioned reaction mechanisms, that is, i) enrichment of Zr, Ti and Al and ii) selective dissolution of Cu and Ni, attain an equilibrium as depicted in
Figure 3 . However, if high anodic current densities are applied, the dissolution rate overcomes the passivation rate, and the sample simply physically degrades. - Electrochemical monitoring tests were also carried out to assess how the treated samples endured long-lasting aggressive solutions (3M NaCl, pH 3) compared to non-treated samples.
-
Figure 4 shows the EIS response (Nyquist plot) carried out over 42 hours of monitoring on a non-treated substrate. The low hand-sideFigure 4 inset highlights the OCP, recorded in between the EIS, whereas the top hand-sideFigure 4 shows a magnification of the recorded EIS. The stability of the non-treated BMG substrate significantly decreases between 15 and 25 hours, the impedance response changing from a capacitive to a kinetic transfer controlled behaviour (see the top hand side inset offigure 4 ). - An optical microscope image of the BMG sample surface after monitoring testing for 42 hours is shown in
Figure 5 . The sample, in addition to be completely whitish on the external surface (signs of formation of insoluble chlorides, ZrCl4 and CuCl) also exhibited two deep greenish-brownish pits, enriched in copper (ca. 70 at. %) and depleted in Zr and other alloying elements. This dissolution mechanism corresponds to pitting corrosion in chloride solutions of Zr, Al and Ti with the simultaneous accumulation of copper. The scanning-electron microscope image of the pits (Figure 6 ) shows the corrosion pits after 42 hours of sample exposure to the solution. - On the other hand, EIS monitoring tests carried out on the BMG substrate, treated according to the invention, shows a rather stable capacitive response during a monitoring time of 72 hours (
Figure 8 ). The substrate does not show any visible signs of corrosion after testing. For instance,Figure 7 shows the absence of whitish surface portions and of greenish-brownish pits. - Indeed, the impedance response recorded over the time interval was observed to be rather stable and to have a capacitive behaviour up to 67 hours. The recorded OCP starts at values of approximately -0.15 V, decreases down to approximately -0.25 V and then steadily increases attaining values of -0.10 V (inset of
Figure 8 ). No OCP scattering (common sign chemical instability) was observed on treated samples. - Ageing tests were also performed on treated and non-treated BMG substrates. Corrosion observations and statistical analysis were then carried out on the different samples and results are listed in Table 1. The total counted defects were determine to be 35 and 13 for the non-treated substrates and for the anodically treated substrates (invention), respectively. The average corrosion defects on the non-treated substrates was calculated to be 3.5 ± 1.6 per sample, whereas 1.3 ± 1.1 for the treated substrates, respectively.
Table 1: Corrosion test on treated BMG substrates (invention) and non-treated BMG substrates. Sample Ref. Non-Treated / Corrosion defects Anod. Treated / Corrosion defects 1 3 1 2 4 2 3 4 3 4 2 3 5 6 1 6 6 1 7 3 1 8 3 0 9 3 0 10 1 1 Total 35 13 Average 3.5 ± 1.6 1.3 ± 1.1 - 1. Salt-fog-chamber test, according to the standard NIHS 96-50,
- 2. Thermal shock test, according to the standard NIHS 96-50,
- 3. Moist-heat tests, according to the standard NIHS 96-50,
- 4. Artificial sweat test, according to the standard NIHS 96-50.
Claims (15)
- A process for enhancing corrosion resistance of a metal-based glass substrate, wherein the metal of the metal-based glass is one or more of zirconium, titanium, hafnium, aluminium, magnesium, and gold,
wherein the process comprises a step of exposing the substrate to an electrochemical anodic treatment applying a current density from 0.5 mA.cm-2 to 1000 mA.cm-2. - Process according to claim 1, characterized in that the electrochemical anodic treatment is carried out with a current density from 10 to 500 mA.cm-2.
- Process according to claim 1 or 2, characterized in that the current density is applied for 5 and 300 seconds, preferably for 30 to 90 seconds.
- Process according to any one of claims 1 to 3, characterized in that the electrochemical anodic treatment is carried out in an aqueous solution having a pH ranging from 0 to 6.
- Process according to any one of claims 1 to 4, characterized in that the electrochemical anodic treatment is carried out in an aqueous solution comprising one or more of sulfuric acid, phosphoric acid, oxalic acid, citric acid, perchloric acid, and nitric acid, preferably a mixture of sulfuric acid and phosphoric acid.
- Process according to any one of claims 1 to 5, characterized in that the electrochemical anodic treatment is carried out at a temperature preferably ranging from 5° C to 60° C, more preferably from 20° C to 40° C.
- Process according to any one of claims 1 to 6, characterized in that the electrochemical anodic treatment is carried out in an aqueous solution comprising one or more complexing agent selected from the group consisting of ethylenediaminetetraacetic acid, citrate, ethylenediamine, and oxalate.
- Process according to any one of claims 1 to 7, characterized in that the metal-based glass substrate is selected from the group consisting of zirconium, titanium, hafnium, aluminium, magnesium, and gold-based alloys.
- Process according to any one of claims 1 to 8, characterized in that the metal-based glass substrate is zirconium based.
- Process according to any one of claims 1 to 9, characterized in that the process comprises a step of surface finishing, such as at least one of polishing, brushing, staining and sandblasting polishing, the metal-based glass substrate prior to the electrochemical anodic treatment.
- Process according to any one of claims 1 to 10, characterized in that the process comprises a step of degreasing the metal-based glass substrate prior to the electrochemical anodic treatment, preferably after a surface finishing step.
- Process according to any one of claims 1 to 11, characterized in that the process comprises a step of chemically passivating the metal-based glass substrate before and/or after the electrochemical anodic treatment, using nitric acid, sulfuric acid, oxalic acid, and citric acid, preferably citric acid or a mix of them, with concentration ranging from 10-3 M to 2 M (mol.L-1) and a temperature from 5°C to 60°C, more preferably from 20°C to 40°C, for instance at 25°C.
- Process according to any one of claims 1 to 12, characterized in that the process comprises a pre-treatment, carried out before the electrochemical anodic treatment, including the following sequence:a) surface finishing the metal-based glass substrate,b) optionally rinsing the metal-based glass substrate with deionized water,c) degreasing the metal-based glass substrate,d) optionally rinsing the metal-based glass substrate with deionized water,e) passivating the metal-based glass substrate,f) optionally rinsing the metal-based glass substrate with deionized water.
- Process according to any one of claims 1 to 13, characterized in that the electrochemical anodic treatment is carried out with a current density from 10 to 500 mA.cm-2 for 5 and 300 seconds, preferably for 30 to 90 seconds, in an aqueous solution having a pH ranging from 0 to 6, at a temperature preferably ranging from 5° C to 60° C, wherein the metal-based glass is zirconium based.
- Luxury component or good comprising a metal-based glass substrate obtained according to any one of claims 1 to 14, wherein luxury includes horology, jewellery, leather goods, writing accessories, ornaments and fashion.
Priority Applications (1)
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EP20196233.9A EP3967791A1 (en) | 2020-09-15 | 2020-09-15 | Enhanced corrosion resistance process for bulk metallic glass substrates |
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EP20196233.9A EP3967791A1 (en) | 2020-09-15 | 2020-09-15 | Enhanced corrosion resistance process for bulk metallic glass substrates |
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Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040121290A1 (en) * | 2002-09-16 | 2004-06-24 | Lynntech, Inc. | Biocompatible implants |
EP1772535A1 (en) * | 2004-05-28 | 2007-04-11 | Ngk Insulators, Ltd. | Method for coloring surface of zirconium-based metallic glass component |
CN104178716B (en) * | 2014-07-31 | 2016-06-08 | 郑州大学 | A kind of optimization technique improving ZrCuNiAlTi block metal glass corrosion resisting property |
CN109680316A (en) * | 2019-02-28 | 2019-04-26 | 安徽工业大学 | A kind of method of zirconium-based metallic glass surface preparation structure color film layer |
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2020
- 2020-09-15 EP EP20196233.9A patent/EP3967791A1/en active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040121290A1 (en) * | 2002-09-16 | 2004-06-24 | Lynntech, Inc. | Biocompatible implants |
EP1772535A1 (en) * | 2004-05-28 | 2007-04-11 | Ngk Insulators, Ltd. | Method for coloring surface of zirconium-based metallic glass component |
CN104178716B (en) * | 2014-07-31 | 2016-06-08 | 郑州大学 | A kind of optimization technique improving ZrCuNiAlTi block metal glass corrosion resisting property |
CN109680316A (en) * | 2019-02-28 | 2019-04-26 | 安徽工业大学 | A kind of method of zirconium-based metallic glass surface preparation structure color film layer |
Non-Patent Citations (1)
Title |
---|
A. GEBERTP. GOSTINL. SCHULTZ: "Effect of surface finishing of a Zr-based bulk metallic glass on its corrosion behaviour", CORR. SCI., vol. 52, 2010, pages 1711 - 1720, XP026966870 |
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