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WO2007073213A1 - Procede de depot sans courant a l’aide d’un micro-arc - Google Patents

Procede de depot sans courant a l’aide d’un micro-arc Download PDF

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Publication number
WO2007073213A1
WO2007073213A1 PCT/NZ2006/000336 NZ2006000336W WO2007073213A1 WO 2007073213 A1 WO2007073213 A1 WO 2007073213A1 NZ 2006000336 W NZ2006000336 W NZ 2006000336W WO 2007073213 A1 WO2007073213 A1 WO 2007073213A1
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Prior art keywords
peo
substrate
nickel
carrying
electrolyte
Prior art date
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Ceased
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PCT/NZ2006/000336
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English (en)
Inventor
Wei Gao
Zhenmin Liu
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Auckland Uniservices Ltd
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Auckland Uniservices Ltd
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Priority to US12/158,535 priority Critical patent/US20090223829A1/en
Publication of WO2007073213A1 publication Critical patent/WO2007073213A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1848—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by electrochemical pretreatment
    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
    • C23C18/1827—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment only one step pretreatment
    • C23C18/1834—Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers
    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • 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
    • C25D11/026—Anodisation with spark discharge
    • 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
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • 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
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • 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
    • 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
    • C25D11/30—Anodisation of magnesium or alloys based thereon
    • 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
    • C25D11/34—Anodisation of metals or alloys not provided for in groups C25D11/04 - C25D11/32
    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
    • C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites

Definitions

  • the invention relates to electtoless plating methods which involve a pre-step of plasma electrolytic oxidation.
  • magnesium (Mg) and Mg alloys are finding increasing application in various industries because of a number of desirable properties. These include high specific strength and stiffness, and excellent castability, machinability and damping properties.
  • the driving force also lies in the greatly improved affordability of commercial Mg alloys.
  • Mg and Mg alloys exhibit great promise.
  • the high chemical reactivity of Mg results in poor corrosion resistance. This is one of the main obstacles to the applications of Mg alloys in practical environments.
  • providing a protective surface treatment is an essential part of the manufacturing process for many Mg components.
  • electroless nickel (EN) plating is of particular interest. It has advantages such as uniform deposition, good corrosion and wear resistance, good electrical and thermal conductivity, and good solderability.
  • Electroless nickel (Ni) coatings on steels, Mg alloys, aluminium (Al) and copper (Cu) have been investigated during the past few years.
  • Previous studies of electroless nickel coatings on Mg alloys, such as the Dow method, DeLong et al, described in US patent 3,152,009 use basic nickel carbonate as the main salt in order to minimize the corrosion tendency of the Mg alloy substrate in the plating bath. This corrosion results in high cost and low efficiency — see Fatigue properties of Keronite coatings on a magnesium alloy (Surface and Coatings Technology, 2004.
  • a method for electroless plating of a substrate comprising the steps of forming a layer of oxide on the substrate by plasma electrolytic oxidation (PEO), and depositing a layer comprising nickel on the substrate by electroless nickel (EN) deposition.
  • PEO plasma electrolytic oxidation
  • EN electroless nickel
  • the PEO step of comprises or results in formation of a very thin layer of dense oxide.
  • the substrate is selected from magnesium, aluminium, titanium, copper and their alloys, and iron alloys.
  • the PEO step is ceased when the voltage reaches 450V, preferably with current density varying from 0 to 1000A/m "2 .
  • the PEO step is ceased when a high density of nucleation sites are formed.
  • the step of chemical deposition of palladium onto the substrate Preferably between the PEO step and the EN step there is the step of chemical deposition of palladium onto the substrate.
  • a pre-treatment step of polishing the substrate Preferably before or after any or all of the steps of polishing, PEO, EN, chemical deposition of palladium and reduction of palladium ions the substrate is washed or cleaned with water.
  • the EN is carried out by contacting the substrate with a bath containing nickel ions.
  • the bath includes nickel ions and phosphorous ions.
  • the pH of the bath is between 6-8 and most preferably the temperature is around 80 0 C.
  • Figure 2 shows a typical EN experimental set up
  • Figure 3 illustrates potentiodynamic polarization curves for AZ91 alloy, PEO coating and PEO + EN coatings of the invention.
  • Figure 4 illustrates potentiodynamic polarization curves for AZ91 alloy, traditional EN and PEO + EN coatings of the invention.
  • Figure 5 shows micrographs of surface morphology of (a) AZ91 alloy and (b) PEO coated
  • Figure 7 shows SEM images of sample surface for: (a) Dow method pretreated, (b) PEO pretreated, (c) Dow method EN coating for 4 min, and (d) PEO + EN coating for 4 min, (e) Dow method EN coating for 60 min, (f) PEO + EN for 60 min
  • Figure 8 shows the cross-sectional morphology of (a) Dow method EN coating and (b) PEO + EN coaling of the invention.
  • Figure 9 presents plots of EDS chemical analysis across the interface for: (a) traditional EN coating, and (b) PEO + EN coating of the invention.
  • Figure 10 presents a friction plot for the scratch tests of conventional EN on AZ91 alloy substrate.
  • Figure 11 shows a micrograph of a scratch track of an adhesion test on a conventional EN coating.
  • Figure 12 presents a friction plot for scratch tests of the EN coating prepared by the method of the invention on AZ91 alloy substrate;
  • Figure 13 shows a micrograph of a scratch track of an adhesion test on a EN coating of the invention.
  • Figure 14 shows micrographs of the ends of scratch tracks on EN coatings: a) conventional EN coating and b) an EN coating of the invention.
  • the invention relates to providing resistant coatings for metal or metal alloys such as, but not limited to magnesium and magnesium alloys. Coatings may also be formed on titanium, aluminium, copper, and iron and their alloys.
  • Coatings which are successful in protecting a metal from corrosion are ideally uniform, well adhered, pore-free, and have a self-healing ability.
  • the invention prior to carrying out electroless nickel (EN) plating or deposition on a metal or metal alloy substrate there is a pre-step of plasma electrolytic oxidation (PEO).
  • PEO plasma electrolytic oxidation
  • the method of the invention does not require the use Cr 6+ , cyanide or HF in its pretreatment, and therefore is a more environmentally friendly process.
  • Important steps of the method of the invention comprise: plasma electrolytic oxidation, and electroless nickel plating.
  • Plasma electrolytic oxidation (PEO) or deposition has been used in the prior art to prepare coatings on Fe, Al, Ti and Mg metal and/ or alloys.
  • PEO is a spark-anodizing oxidation method. It involves the modification of a conventionally anodically grown film by the application of an electric field greater than the dielectric breakdown field for the oxide. Discharges occur and the resulting plasma-chemical reactions contribute to the growth of the coating.
  • the technique is friendly to the environment because no chromate solution is needed.
  • PEO is carried out to produce a very thin layer of preferably dense and preferably continuous oxide.
  • oxide of the PEO step provides high density of nucleation sites for the next stage electroless coating.
  • a typical PEO set up is illustrated in Figure 1 and comprises power supply 1, working electrodes 2 and electrolyte 3. This is in a bipolar micro-arc oxidation treatment mode where both electrodes are the substrates to be treated. No counter electrode is required.
  • the degree of PEO sufficient to be effective will depend upon the substrate and the conditions however, for Mg and Mg alloys the voltage usually progresses from low to high, 0 to 450 V; current density from 0 to 1000 A/m 2 over 2 to 10 minutes. This will also apply for many types of electrolyte which can produce a dense, continuous protective layer on substrates such as aluminium, titanium and steels.
  • the preferred conditions for the PEO process include one or more of the following:
  • the electrolyte is an alkaline-based solution
  • the current density should be kept in the region up to 1000A/m 2 , and ideally not exceeding 1000A/m 2 , for at least 2 minutes.
  • Example electrodes include Al, Ti and Mg and Fe. It is their ability to form oxide coatings which makes them suitable.
  • single oxides eg Al 2 O 3 , TiO 2 or MgO
  • mixed oxides will be produced on the substrate surface.
  • the use of a set of phosphate based alkaline electrolytes plus additives can produce mixed oxide coatings.
  • sodium hydroxide 2-5g, sodium phosphate 2-5g, and sodium silicate 0.5-lg produce magnesium oxide content and a small amount of hydroxides and silicates. Some hydroxide and oxide may benefit the subsequent nickel nucleation.
  • Our preferred conditions are listed in Stage 1 of Table 2.
  • Electroless nickel (EN) plating is a chemical reduction process which depends upon the catalytic reduction of Ni ions in an aqueous solution (containing a chemical reducing agent) and the subsequent deposition of Ni-P alloys or Ni-B alloys without the use of electrical energy.
  • Ni-P alloy coatings are more common in the art.
  • the deposits typically contain P in the range 3- 13% by weight.
  • Ni-B alloy coatings are more common in industrial wear applications for their "as-plated” hardness, which is higher than Ni-P.
  • Poly alloys are a combination of Ni, B or P and other metals such as Co, Fe, W, Re or Mo.
  • Figure 2 illustrates a typical EN set up comprising a heating element 4, the substrate to be coated 5, electrolyte 6, and an agitator or stirrer 7.
  • suitable electrolytes may include all kinds of traditional alkaline and acidic based electroless nickel plating electrolytes as is well known in the art.
  • Nickel sulphate or carbonate are preferred as in nickel salts.
  • a preferred electrolyte is as documented in Stage 4 of Table 1. This will result in a phosphorous concentration of the final Ni-P coating is 6-10 wt%. However other phosphorous concentrations are possible, within the scope of the invention.
  • General EN process conditions include control of temperature of the electrolyte, pH of the electrolyte, and chemical concentrations.
  • a preferred embodiment of die invention has an electrolyte temperature of around 80°C, and a pH between 6-8.
  • the process is preferably carried out under ambient atmospheric conditions with some gentle stirring.
  • Table 1 - Preferred Plating Process Stages
  • the activation step again assists in preparation of dense and effective catalytic nucleation sites for the subsequent electroless nickel plating.
  • This step involves the chemical deposition of Pd metal onto the substrate surface. Well-distributed fine Pd particles are formed on the surface. To activate the surface other materials such as nickel may be alternatively used.
  • Our preferred process may include the use of PdCl 2 to provide the source of Pd adatoms for the subsequent catalytic sites.
  • the reduction step is mainly to control the amount of Pd deposition. It can reduce the effect of possible over-doping of Pd ions in the electroless nickel plating bath or nickel atoms on the substrate (such as Mg) surface, which will again prolong the lifetime of the bath and improve the quality of nickel plating.
  • the preferred process it involves the use of sodium hypophosphite to reduce the Pd ions into Pd atoms on the surface.
  • the NaOH provides the pH value required and produces magnesium oxides
  • NaH 2 PO 4 helps to produce magnesium phosphate on the surface.
  • Sodium silicate acts as a corrosion resistant agent for the magnesium alloy.
  • the Nickel sulphate provides the source of nickel ions for the nickel plating. A very small amount of HF helps to dissolve the nickel sulphate and acts as corrosion resistant buffer. This small amount is not detrimental.
  • nickel carbonate is used.
  • the citric acid acts as a complexant (to reduce the plating speed and keep the bath stable)
  • ammonium bifluoride acts as buffer
  • sodium hypophosphite is the main reductant
  • ammonium hydroxide is used to adjust the pH value of the electroless nickel bath.
  • the potentiodynamic polarization measurement in 3.5 wt. %NaCl solutions was carried out to compare the corrosion behaviour of the uncoated Mg alloy, PEO coated and PEO + EN coated samples.
  • the polarization range was from -2.0 to +0.2 V versus saturated calomel electrode.
  • the polarization scanning rate was 40 mV/min.
  • the neutral salt spray test (NSST) was also carried out for 168 hours according to ASTM Bl 17-97 standard. Specimens were inspected daily.
  • the morphology and microstructure of the deposits were examined by means of optical microscopy and scanning electron microscopy (SEM, Philips XL30S) with a field emission gun. Energy-dispersive spectroscopy (EDS) and XPS were used to analyse the chemical composition and states. The structure of the deposits was also determined by using a D8 advanced X-ray diffractometer.
  • Al and Zn are the main alloying elements in AZ91 alloy (Table 2).
  • the alloy consists of two phases as shown in Figure 6a.
  • the ⁇ -Mg matrix is a Mg-Al-Zn solid solution widi the same crystal structure as pure Mg, and the ⁇ precipitates are intermetallic phase Mg 17 A 112 .
  • This intermetallic compound segregated at grain boundaries, has a free corrosion potential of -1.0 V, while the OC- phase has a free corrosion potential of -1.73 V. Therefore, the intermetallic compound would provide some advantages for the nucleation during the PEO treatment.
  • the PEO coating clearly shows a few peaks of MgO by means of XRD pattern result.
  • FIG. 3 shows potentiodynamic polarization curves for the uncoated Mg alloy and the specimens with PEO coating and PEO + EN coating in 3.5 wt.%NaCl solution at room temperature.
  • Chlorine content was high around die corroded area in Figure 5 by EDS analysis, indicating diat Cl- is corrosive and associated witii MgO and Mg(OH) 2 -
  • the corrosion resistance was greatly improved, and passivation occurred during anodic polarization. There is no obvious pitting corrosion when the applied potential reaches 200 n ⁇ V.
  • FIG. 6 shows photos of the typical morphologies of specimens after 168h neutral salt spray testing. There is no noticeable galvanic corrosion pits on the surface of the PEO and PEO + EN coatings, demonstrating that the PEO coating and the new PEO + EN coating have better corrosion resistance than that of Mg alloy and the conventional EN coating. As discussed above, the two phases, ⁇ -Mg matrix and the P-Mg 17 A j12 , have very different corrosion behaviour. Therefore galvanic corrosion took place around the phase boundaries as shown in Figure 6a.
  • Figure 7 shows SEM micrographs of the samples at different treatment stages.
  • Figures 7a and 7b show a AZ91 sample surface pretreated by Dow pre-treatments (7a) and after PEO pretreatment (7b). It can be clearly seen from Figures 7a and 7b that the traditional treatment does not produce a uniform and dense protective fUm before EN plating. More importantly, the PEO processing only requires one-step pre-treatment rather than three-step operations which are typical of the prior art, and eliminates the use of hazardous chemicals such as chromium acid and hydrofluoric acid. Furthermore, we found that the nucleation mechanism is also different.
  • Figures 7c and 7d show the surface after conventional EN coating (4 minutes) (7c) and after PEO, +EN coating for 4 minutes (Jd).
  • the prior art EN coatings have been discussed as being preferentially nucleated on the ⁇ -phase or in the vicinity, resulting in non-uniform distribution.
  • the nucleation of the new EN processing is quite uniform on the PEO pre-treated surface, and the nucleation density is higher than that of the traditional process. This indicates that the PEO pre- treatment eliminates the effect of the electrochemically heterogeneous AZ91 substrate surface. Consequently, the final surface of the new EN coating (Fig. 7f) is smoother and more uniform than that of the Dow EN coating as shown in Figures 7e.
  • the nodular si2e in Figure 7f is about 10 ⁇ m or less whereas the nodular size of the traditional EN surface is often bigger than 50 ⁇ m, as shown in Figure 7e.
  • the coarse nodular structure in Figure 7e probably contains more pores around the nodular and substrate grain boundaries. Therefore, it can be concluded that the new PEO + EN coating provides a less porous duplex coating than the traditional one, and hence reduces the possible galvanic corrosion between the Ni coating and Mg substrate significantly.
  • FIG 8 shows SEM cross-sectional morphology of two types of EN coatings on AZ91 alloy. It can be seen that the traditional EN process produces a rough and heterogeneous interface (8a) between the EN and the substrate due to the strong etching effect of chromium acid (CrO 3 ). However the interface between the new EN and the substrate (8b) is relatively smooth, and the coating has a more uniform thickness and smoother surface, as shown in Figures 6b and 6f.
  • Figures 9a and 9b show the EDS chemical analysis along the white lines in Figures 8a and 8b. It can be seen that oxygen concentration is lower than fluorine around the interface region in Figure 9a. It can be seen from Figure 8b that oxygen content is higher than fluorine and the range of oxygen is much wider (5 ⁇ m) than that of the traditional EN ( ⁇ 2 ⁇ m, indicating that PEO pre- treatment in the new EN process produces an oxide film of ⁇ 5 ⁇ m thick. Moreover, it can also be found that the oxygen concentration gradually increased to ⁇ 25 wt.% around the interface region in Figure 9b, indicating that the PEO technique can produce gradient coatings.
  • Figures 10 and 12 are plots of the measured friction force (Fx) vs. loading (Fz) for two coatings.
  • Figure 9 is the plot for the scratch tests of a conventional EN on AZ91 substrate, whilst Figure 12 is for an EN coating prepared on AZ91 substrate in accordance with the invention.
  • An increasing load was applied via a diamond tip which was moving on the top surface of the coatings.
  • the measured Fx shows the increasing wear force with increasing load.
  • the transition point (critical load, Lc) indicates the penetrating of the coating, which can be considered as reflecting the adhesion strength of the coating.
  • Figure 11 shows the scratch track of the adhesion test on the conventional EN coating whilst Figure 13 shows the track for the coating of the invention.
  • Figure 14 illustrates the ends of scratch tracks on EN coatings (a) conventional EN, (b) the invention EN (the arrows point in the scratching direction), that the failure behaviour is different for the two coatings, probably due to the different interface structure for the two coatings (a: MgF 2 , b: MgO).
  • the scratch track on the EN coating produced by the method of the invention is narrower than that on the conventional EN. This may be attributed to the different hardness of the interlayer.
  • the PEO film as the interlayer has a higher hardness than the conventional one.
  • Salt fog spray and potentiodynamic polarization testing demonstrate that the PEO treatment produces a dense, well adhered oxide coating on the AZ91 Mg alloy.
  • the presence of the PEO film between the nickel plating and the substrate acted as an effective barrier layer, and also provided high density nucleation sites after activation treatment for the subsequent EN coaling, which can significantly reduce the porosity of the nickel coating. Therefore, the coatings produced via PEO + EN process possess superior corrosion resistance to salt spray testing as compared to the traditional EN coatings.
  • Potentiodynamic polarization tests also indicated that the corrosion current density of the new coating on AZ91 decreased by at least two orders of magnitudes. This new coating process does not need Cr 6+ and HF, and is therefore more environmentally friendly.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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Abstract

La présente invention concerne un procédé de dépôt sans courant d’un substrat tel que le magnésium, l’aluminium, le titane ou un alliage, comprenant les étapes consistant à former une couche très mince d'oxyde sur le substrat par oxydation électrolytique au plasma avant le dépôt d’une couche comprenant du nickel sur le substrat par dépôt de nickel sans courant.
PCT/NZ2006/000336 2005-12-20 2006-12-20 Procede de depot sans courant a l’aide d’un micro-arc Ceased WO2007073213A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US12/158,535 US20090223829A1 (en) 2005-12-20 2006-12-20 Micro-Arc Assisted Electroless Plating Methods

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NZ544373 2005-12-20
NZ544373A NZ544373A (en) 2005-12-20 2005-12-20 Micro-arc plasma assisted electroless nickel plating methods

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WO2007073213A1 true WO2007073213A1 (fr) 2007-06-28

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NZ (1) NZ544373A (fr)
WO (1) WO2007073213A1 (fr)

Cited By (12)

* Cited by examiner, † Cited by third party
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EP2055419A1 (fr) * 2007-11-05 2009-05-06 Magtech Technology Co., Ltd Procédé de brasage de pièce en alliage de magnésium avec dépôt anélectrolytique de Nickel-Phosphore, d'un flux et d'un alliage de brasure sans plomb à base d'étain
DE102008026557A1 (de) 2008-06-03 2009-12-17 Königsee Implantate und Instrumente zur Osteosynthese GmbH Elektrochemisch hergestellte, biologisch degradationsstabile, duktile und haftfeste Titanoxid-Oberflächenschicht auf Titan oder Titanbasislegierungen
DE102008026558A1 (de) 2008-06-03 2010-01-14 Königsee Implantate und Instrumente zur Osteosynthese GmbH Elektrochemisches Tauchverfahren in einem wässrigen Elektrolyt zur Erzeugung einer biologisch degradationsstabilen Oberflächenschicht auf Grundkörpern aus Titan oder Titanbasislegierungen
CN101994146A (zh) * 2009-08-25 2011-03-30 威斯科高新技术有限公司 镁合金制品用peo表面处理溶液的组合物
KR101115123B1 (ko) 2009-08-07 2012-03-08 주식회사 위스코하이텍 마그네슘합금의 전기 도금용 플라즈마 표면처리 용액제조방법
CN103060881A (zh) * 2013-01-25 2013-04-24 北京科技大学 钛合金表面黑色抗高温氧化涂层制备方法
CN103668391A (zh) * 2012-09-13 2014-03-26 汉达精密电子(昆山)有限公司 镁合金表面仿电镀处理方法及其产品
CN103695985A (zh) * 2013-12-16 2014-04-02 电子科技大学 一种镍氢电池镍电极表面制备氧化钛涂层的方法
CN104583462B (zh) * 2012-07-30 2017-07-28 东莞勤德五金制品有限公司 镁材与树脂零件的复合品及其制造方法
CN107460515A (zh) * 2016-06-06 2017-12-12 宁波瑞隆表面技术有限公司 一种铝合金微弧氧化-化学镀镍复合涂层的制备方法
CN108277516A (zh) * 2018-04-13 2018-07-13 中国人民解放军陆军装甲兵学院 一种微弧氧化电解液和一种微弧氧化膜的制备方法
CN110042443A (zh) * 2019-05-16 2019-07-23 苏州凯宥电子科技有限公司 一种铝合金的环保型连续表面处理工艺

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CN105543920B (zh) * 2015-12-10 2017-11-28 嘉瑞科技（惠州）有限公司 镁合金微弧氧化层表面制备导电涂层的处理方法
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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2055419A1 (fr) * 2007-11-05 2009-05-06 Magtech Technology Co., Ltd Procédé de brasage de pièce en alliage de magnésium avec dépôt anélectrolytique de Nickel-Phosphore, d'un flux et d'un alliage de brasure sans plomb à base d'étain
DE102008026557A1 (de) 2008-06-03 2009-12-17 Königsee Implantate und Instrumente zur Osteosynthese GmbH Elektrochemisch hergestellte, biologisch degradationsstabile, duktile und haftfeste Titanoxid-Oberflächenschicht auf Titan oder Titanbasislegierungen
DE102008026558A1 (de) 2008-06-03 2010-01-14 Königsee Implantate und Instrumente zur Osteosynthese GmbH Elektrochemisches Tauchverfahren in einem wässrigen Elektrolyt zur Erzeugung einer biologisch degradationsstabilen Oberflächenschicht auf Grundkörpern aus Titan oder Titanbasislegierungen
KR101115123B1 (ko) 2009-08-07 2012-03-08 주식회사 위스코하이텍 마그네슘합금의 전기 도금용 플라즈마 표면처리 용액제조방법
CN101994146A (zh) * 2009-08-25 2011-03-30 威斯科高新技术有限公司 镁合金制品用peo表面处理溶液的组合物
CN104583462B (zh) * 2012-07-30 2017-07-28 东莞勤德五金制品有限公司 镁材与树脂零件的复合品及其制造方法
CN103668391A (zh) * 2012-09-13 2014-03-26 汉达精密电子(昆山)有限公司 镁合金表面仿电镀处理方法及其产品
CN103060881A (zh) * 2013-01-25 2013-04-24 北京科技大学 钛合金表面黑色抗高温氧化涂层制备方法
CN103695985A (zh) * 2013-12-16 2014-04-02 电子科技大学 一种镍氢电池镍电极表面制备氧化钛涂层的方法
CN107460515A (zh) * 2016-06-06 2017-12-12 宁波瑞隆表面技术有限公司 一种铝合金微弧氧化-化学镀镍复合涂层的制备方法
CN108277516A (zh) * 2018-04-13 2018-07-13 中国人民解放军陆军装甲兵学院 一种微弧氧化电解液和一种微弧氧化膜的制备方法
CN108277516B (zh) * 2018-04-13 2022-09-27 中国人民解放军陆军装甲兵学院 一种微弧氧化电解液和一种微弧氧化膜的制备方法
CN110042443A (zh) * 2019-05-16 2019-07-23 苏州凯宥电子科技有限公司 一种铝合金的环保型连续表面处理工艺

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