JP2002515092A - Anodizing of magnesium and magnesium alloys - Google Patents

Abstract

(57) Abstract The present invention provides a method for anodizing magnesium or a magnesium-based alloy using an electrolyte solution (preferably derived primarily from phosphoric acid) containing ammonia, an amine, or both. The use of such an aqueous electrolyte solution (which may include other additives), in at least a preferred embodiment, alters the conditions under which anodization can occur and provides a more satisfactory coating on magnesium materials with reduced cycle times. Can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION Anodizing of magnesium and magnesium alloys   The present invention, in at least a preferred embodiment, produces a uniform, corrosion resistant film, In at least preferred embodiments, as pretreatment of another process or magnesium Anodizing method of magnesium and an alloy thereof suitable for final treatment of a rubber article.   Magnesium is a very lightweight yet high strength metal, especially They find use in metal die castings where reduction is desired. In addition, a shield that shields electromagnetic waves Is a good alternative to plastics for applications such as computers and mobile phones Interest is increasing. However, it is a reactive metal and has general effects or Corrosion is a major problem, regardless of the chemical effect.   Various methods of applying a protective anodic oxide film on magnesium metal have conventionally been used. Have been used. These are well-established available for aluminum and its alloys The same results for magnesium articles. It was very difficult to get. This is due in part to the constant The oxide resulting from the volume occupies less volume than the original metal, and therefore has a substantial The oxide film formed on the surface is subjected to tensile stress before the This is caused by cracking and falling off the substrate.   The anodization of magnesium and its alloys often results in a slightly soluble oxide layer It is performed in sulfuric acid. As the formation of the film is outward from the metal substrate, its deposition There is a point where the rate decreases and ultimately the dissolution rate equals the rate of further film growth You. Dissolution of the membrane creates porosity where the movement of ions required for the electrochemical oxidation of the metal occurs. Let it run. This Without these pores, only very thin films would be possible. Electrochemical oxidation pro When the process is completed, the pores are sealed. Anodized aluminum seal is heat This can be done with water or just inorganic chemical solutions.   Of course, similar processes involving magnesium or magnesium alloy They will try to incorporate these features. However, due to the applied tensile stress, There is a complicated problem due to the tendency of the resulting film to crack or break. Also, The use of acidic solutions to anodize gnesium is best for magnesium. Can be seriously attacked by common acids, causing serious problems. Therefore, the present inventor believes that the magnesium solution should be performed in an alkaline solution. You. However, some prior art processes use magnesium fluoride on metal surfaces. Hydrofluoric acid or hydrofluoric acid, which does not attack magnesium to form a protective layer Use salt. It does not dissolve in water and thus protects against further attacks.   Another method of anodizing magnesium or magnesium alloys is described below. Coarse and very multiplicity that forms a good basis for applied paint and other surface coatings It depends on this property to form a porous layer. Generally, such acidic films are It can be formed in very high pH electrolytes containing rehydroxides. This The process is driven by a spark that is coated on a metal substrate To produce a sintered ceramic oxide.   Some dominant methods for anodizing magnesium or magnesium alloys The method consists in seeking to avoid this problem and to form a uniform film. this Is done only by incorporating another species into the film as it forms be able to. Some processes use silicates. Others are ceramic Use material You. Some of these processes involve hydrofluoric acid or hydrofluoric acid, for example, Requires the use of ammonium chloride. These are very harmful substances and the plan Causing irritating odors, safety problems and disposal problems for drivers.   PCT / NZ96 / 00016 (WO96 / 28591) (Barton) Various methods of anodizing magnesium or magnesium alloys have been described. You. This involves anodizing the material in an ammonia containing electrolyte solution. Dissolution The presence of a phosphate compound in the liquid is disclosed.   It is an object of the present invention to replace or replace the process of WO 96/28591. To improve this, a more uniform film can be produced or less The goal is to provide a process that can provide useful options. Summary of the Invention   In one aspect, the invention relates to a method of treating magnesium or magnesium alloy with anodizing acid. This method is   Immerse the magnesium-containing material in the electrolyte as an anode,   Providing a cathode in the electrolyte,   Passing an electric current through the electrolyte,   Including or consisting of Here, the electrolyte has a pH above 7, and   (1) Ammonia or amine or a mixture of these two (preferably ammonia Are present in substantial concentrations ranging from 0.4 to 12 molar) and   (2) phosphoric acid or water-soluble phosphate Or consisting of   Preferably, the phosphoric acid or phosphate is provided in the range of 0.05-0.2 mole. It is. Preferably, the electrolyte includes a blowing agent.   Optionally, the electrolyte comprises a water-soluble peroxide.   Preferably, the amine is used alone in step (1), or the ammonia of step (1) is Wherein the amine is a water-soluble primary, secondary, or palladium compound having a pKa greater than 5. Is a tertiary amine.   Preferably, it has a pKa greater than 9 with the amine.   Preferably, the magnesium or magnesium alloy article is pre- It is cleaned by a processing step.   Preferably, the pre-treatment step comprises:   (A) Dissolution of a mixture of sodium tetraborate and sodium pyrophosphate at 70-90 ° C Immersing the article in the liquid for at least 5 minutes,   (B) 35% by volume of ambient temperature (v / v) hydrofluoric acid for at least 1 minute Immerse the article   (C) over a 1: 1 mixture of 35% by weight hydrofluoric acid and 68% by weight (w / w) nitric acid. Soaking the article for at least one minute.   Preferably, the material is   (I) (a) (1) DC voltage of more than 300 volts (especially more than 350 volts) The electrolyte contains ammonia and no amine), or     (2) DC voltage of 250 volts or more (when the electrolyte is amine or ammonia and Containing min), and   (b) if desired     (1) Normally 0 to 40 volts, sometimes more AC voltage,     (2) Normally 0 to 40 volts, and sometimes higher pulse voltage ( Square wave), and   (II) 50-1000 amps / m^TwoCurrent density, Is anodized using a current having the following characteristics:   Preferably, the current density is between 200 and 350 amps / m^TwoIt is.   In another aspect, the invention relates to magnesium or magnesium alloy (hereinafter referred to as magnesium). Is referred to as "magnesium material").   Providing an electrolyte solution,   Providing a cathode in the solution,   A magnesium-based material is placed as an anode in the solution, and   Pass current between the anode and cathode through its anode to form an anodized surface , Including or consisting of   Wherein the electrolyte has a pH greater than 7,     (a) (1) ammonia and amine or (2) amine, and     (b) (1) at least one source of phosphate ions, and / or (2) aluminate At least one source of nonions and at least one source of fluoride ions; Comprises or consists of in water,   Here, the current applied during anodization is     (A) (1) Hydrogen peroxide and / or soluble peroxide must be present in the electrolyte solution More than 220 volts,       (2) Hydrogen peroxide and / or soluble peroxide must be present in the electrolyte solution More than 210 volts,     (B) providing a significant degree of sparking on the magnesium material, or Its anodized surface as a plasma discharge Than would otherwise be possible without giving a significant degree of sparking on nesium material Higher or its anodized surface and / or plasma discharge is present in the electrolyte anode Not for ammonia and / or amine, less than in each case, Up to the voltage limit.   Preferably, the amine is ammonia gas or an alkali of the volatile amine component. May be present in a neutral solution.   Preferably, the electrolyte solution contains at least one source of phosphate ions.   Preferably, a source of phosphate ions is present, optionally with aluminate or fluoride ions. There is no one.   Preferably, the anodization is performed when the electrolyte solution is below 50 ° C.   Preferably, the voltage limit is above 300 volts and 600 volts for (A) (1). In the case of (A) (2), the voltage exceeds 280 volts and drops below 550 volts.   Preferably, the aqueous electrolyte solution contains at least 3% by weight of ammonia ( When converted to Monia gas).   Preferably, the aqueous electrolyte solution contains at least greater than 5% by weight of ammonia (When converted to ammonia gas).   Preferably, at least one source of phosphate ions is phosphate, soluble phosphate , And soluble ammonium phosphate.   Preferably, the phosphate ions add phosphoric acid to the bath, thereby causing hydrolysis. It is obtained by generating more various phosphate anions.   Preferably, the source of phosphate ions is in the range of 0.01 to 0.2 mole. Exists.   Preferably, the source of phosphate ions is present in the range of about 0.05-0.15 mole. .   Optionally, hydrogen peroxide or soluble peroxide is present.   Optionally, the electrolyte solution may be an aluminate, silicate, borate, fluoride , Phosphates, citrates, and phenols.   Preferably, it does not include significant presence of chromium (III) and chromium (VI).   Preferably, the electrolyte solution is an alkali salt that produces hydroxyl ions by hydrolysis. Not included.   In yet another aspect, the invention relates to a magnesium-based material. (That is, magnesium or magnesium alloy) The law is   Providing an electrolyte solution,   Wherein the electrolyte has a pH greater than 7,     (a) (1) ammonia and amine or (2) amine, and     (b) (1) at least one source of phosphate ions, and / or (2) aluminate At least one source of nonions and at least one source of fluoride ions; Comprises or consists of in water,   Providing a cathode to the solution,   A magnesium-based material is placed as an anode in the solution, and   Pass an electric current between the anode and the cathode through its anode, anodized on the material Surface   Where the ammonium and / or amine in the electrolyte solution Is a process during the anodization process that causes partial melting or melting of the anodized surface layer. Provided in an amount sufficient to avoid park and / or plasma discharges,   Here, the electrolyte solution is water and phosphoric acid provided in a range of 0.1 to 0.2 mol. Comprising or consisting of a source of ions;   Here, the source of the phosphate ion is a group of phosphoric acid and soluble phosphate (for example, Sodium hydrogen phosphate, ammonium hydrogen phosphate, sodium dihydrogen phosphate, phosphorus Diammonium hydrogen oxyacid).   Preferably, the ammonia is at least part of the electrolyte solution when converted to gas. Is also 1% by weight.   Preferably, the magnesium or magnesium alloy has any of the claims Anodized by the method.   Preferably, the magnesium-containing article contains at least 50% by weight of magnesium. Including.   In yet another aspect, the present invention provides an electrolyte solution, a cathode, Including operating an anodizing system of magnesium or magnesium alloy material or Is an anodic oxidation method of magnesium or magnesium alloy consisting of   Here, the electrolyte solution is   (1) one kind of amine or plural kinds of amines, or   (2) a solution containing (a) one or more amines and (b) ammonia in solution; Under electrical input conditions except the introduction of amine and ammonia in the liquid, No anodized coating (due to so-called "sparks" and others).   The presence of weight percent (w / v%) ammonia as a gas referred to in the present application depends on the acid component. It is Wago.   Next, a preferred embodiment of the present invention will be described with reference to the drawings. 1 shows a schematic diagram of an anodizing bath according to an embodiment of the invention. Detailed description of preferred embodiments   WO 96/28591 discloses a magnesium-containing material (magnesium itself) Or an alloy thereof) has been further studied by the present inventors. This process is A conventional mask used for die casting simultaneously with a substantially pure magnesium sample Useful for magnesium alloys such as GN91 and AM60 Has been found.   The process of WO 96/28591 and the process of the invention consist of a bath 1 containing solution 2 The magnesium-containing material 3 is at least partially immersed therein. Can be.   Electrodes 3 and 4 are provided in bath 1 and solution 2, where solution 2 is an electrolyte solution.   Suitable connections, such as cables 5 and 6, are provided to power supply 7 from electrodes 3 and 4.   Solution 2 can include ammonia to an appropriate concentration. Ann in electrolyte solution 2 The concentration of monia can vary. Here, an appropriate range of 1 to 33% by weight. Is desirable for ammonia (converted to gas).   A solution having an ammonia concentration of less than 1% by weight, as disclosed in WO 96/28591 Tends to cause sparks, and the coating formation method is similar to the conventional method of anodizing. The formation of a coating is easier due to the generation of parks. 33% maximum concentration of ammonia Degree acts as an upper limit.   The present inventors have found that the ammonia concentration is 5 to 10% by weight, more preferably 5 to 7% by weight. It has been found that it works properly within the range.   The inventor has determined that the voltage can be in the range of about 220 to 250 Pass appropriate connections (eg, cables 5 and 6) to electrodes 3 and 4 immersed in solution 2. I found that current flows. Prior art anode before the Barton process The oxidation process occurs at 50-150 dc volts, and thus is below the desired level A decrease in ammonia concentration is more likely to allow sparking during the process Before the voltage can reach the appropriate level to form the coating, It should be noted that it is easy to obtain the properties of the anodizing process of the rukari hydroxide . Other embodiments operate the process in the range of about 170-350 DC volts Can be tolerated.   In a process such as this, sparking can occur for several reasons. May occur. Ammonia generally acts to suppress sparks, The concentration of salt in it has a certain effect. If ammonia becomes too low, spark Can occur. Significant increase in phosphate concentration results in complete coating formation Even if it does, spark will be generated at a higher voltage before the voltage rises to that voltage. Sometimes   In a further aspect, a peroxide can be added to the electrolyte solution. Excessive The addition of oxides can reduce the voltage generated by the coating without sparking. Was observed. For example, 5% by weight of ammonia (converted to gas), 0.05 mol Of sodium ammonium hydrogen phosphate and 0.1 mole of sodium peroxide mug The solution of Nesium Hydrogen Peroxide is a 300 dc volt that occurs in the absence of peroxide. A coating very similar to the default coating is formed at 210 dc volts. this Is beneficial under conditions where lower operating voltages are desired.   In addition, when the peroxide level is reduced to 0.05 mol, And no significant difference in the coating has been observed. Also, peroxidation Increasing the substance to 0.2 moles may cause a detrimental spark and may cause Was observed to hinder the formation.   From this criterion, a more preferred embodiment in which about 0.1 mole of peroxide is added Thus, if desired, a lower operating voltage is possible.   When a current is applied to the electrolyte solution 2, the portion 8 of the material 3 immersed in the solution 2 A coating is formed on the material 3 forming the anode of FIG. The process itself is To a large extent it is self-terminating and the current drawn by the anodizing bath 1 is It decreases as the thickness of the coating over portion 8 increases. In this way, the anodic acid The arrangement of the article 3 as an anode in the oxidizing bath 1 causes the current to flow until a coating is formed. Tend to draw in and substantially isolate the magnesium in material 3 from electrolyte solution 2 When there is enough coating to stand, the current drops and the coating Can be functioned as an indication that the operation has been performed.   Dissolve various additives to change the final coating and its appearance Liquid 2 can be added. For example, phosphate compounds are anodized aluminum It can be used to give a finish similar to N, given in the range of 0.01 to 0.2 mol. It has been found that the phosphate compounds can be suitable. In general, Concentrations less than 0.01 mole tend to give a slightly clear finish. 0.2 mole Higher concentrations result in an opaque finish that again changes the appearance of the final product. Rin Phosphate compounds such as sodium ammonium hydrogen oxyde If a finish similar to the appearance of chromium is to be imparted, 0.05 to 0.15 mol is preferred. New range is appropriate Has been issued. Ammonium phosphate is particularly useful; Compounds have been found to be a direct alternative.   Anodizing with ammonium phosphate compound provides significant corrosion resistance to coatings Give sex. The coating can also be further coated with paint or other organic sealer. Suitable for printing.   In another preferred embodiment of the present invention, electrolyte solution 2 comprises dihydrogen phosphate Ammonium or alternatively or additionally, such as diammonium hydrogen phosphate Compounds can be included. All of these compounds are ammonium hydrogen phosphate Commercial quantities for the anodization process compared to compounds such as sodium And is readily available.   An alternative additive that gives a finish similar to anodized aluminum is phosphated It has been found that the same concentration of fluoride and aluminate as the compound is used . Common compounds such as sodium aluminate and sodium fluoride The concentration is 0.05 molar for each of these compounds. Sodium aluminate And when the concentration of sodium fluoride increases to 0.1 mol, the finish becomes a pearly finish Change. This is aesthetically pleasing in itself, but anodized aluminum Cannot be directly compared to, therefore, manufacturing components of the same product from different materials It is desirable to be able to match the finish of the products of Luminium and Magnesium Not good.   The process itself has a higher rate than the traditional anodization of the magnesium process. Is performed at a low current. The drawing current is 1m2 on the magnesium surface. It is on the order of 100 amps. Low current and no sparking The alkali hydroxides conventionally used, while reducing the temperature rise in bath 1, Compared to bathing To produce a coating of equivalent thickness. The decrease in the temperature rise of this bath Resulting in a significant reduction in the cooling equipment required to perform   The presently preferred embodiment of the present invention is performed at room temperature and is not required, but is Preferably, an extreme oxidation process is performed.   Selection of additives includes phosphate additives and / or fluoride additives. It should be noted that Fluoride additives instead of phosphate additives When used, it poses a greater problem for disposal of the solution. Fluorine compound Are environmentally costly because of the strictest environmental regulations on wastewater and waste. to this Phosphate compounds, on the other hand, are relatively less harmful to the environment and for this reason alone. Is also preferred.   Additives can also include sealants and other compounds, aluminates, Silicates, borides, fluorides, phosphates, citrates and phenols Many additives used in conventional anodizing processes such as can be used You.   The coating formed on magnesium is magnesium oxide, magnesium hydroxide Coating coating of the additional components with the calcium and the specific additives used in the process Can be a wing. For example, provided sodium ammonium hydrogen phosphate The embodiments provided result in a component of magnesium phosphate in the coating. Also, The manner in which the fluoride and the aluminate compound are provided is such that the finish coating has It can result in the presence of magnesium iodide and magnesium aluminate.   Also, the use of ammonia in the solution can be achieved by using ventilation in the area around the anodic oxidation bath 1. It should be noted that may be required.   Also, the process of the present invention uses a conventional alkali hydroxide solution. It tends to give the coating slightly faster than.   The most preferred electrolyte composition using ammonia alone is     3.0 to 3.0 mol as ammonia^*(Usually made with 25% aqueous solution)     0.1 to 0.2 mol as phosphoric acid (or phosphate may be used) ,as well as     The nonionic foaming agent is 0.1 ml per liter as the foaming agent.   This bath has a pH of about 11.6.^* The ammonia concentration is between 3.0 and 3.3 molar after the addition of phosphoric acid, The ammonia added to the bath initially is slightly higher.   The blowing agent ideally acts to reduce ammonia loss to the atmosphere To   The most preferred electrochemical conditions for anodizing with such a composition are:   (I) (1) 350 to 500 V as a DC voltage end point, depending on a desired film thickness,   As desired   (2) (a) 0-40 V as a set point of AC voltage, and / or   (2) (b) 0-40 V as a set point of the pulse voltage, and   (II) 150 to 400 amps / cm as DC current density of bulk^Two It is.   The temperature is between 0 and 35C (most preferably between 10 and 30C).   The present invention provides that the partial or complete replacement of ammonia by an amine has been previously described in the present invention. It is disclosed in WO 96/28591 under the conditions described. It is recognized that the process can be performed by separately operating.   Simple amines such as methylamine and ethylamine are volatile and have substituents It is recommended to include longer chains or more complex amines. Suitable amines are few Must be water-soluble up to a level of at least 3.0 mol, equivalent to ammonia Must be basic (hydroxyl OH in solution^-Ion can be generated When). Some examples of amines that can be used include diethylenetriamine and ethanol. Amine.   As noted above, various anodizing voltages can be used, most preferably 250 volts. In some cases, an additional AC voltage may be required which is greater than the flow volts.   Next, some preferred embodiments of the present invention will be described with reference to examples. Example 1   AZ91D magnesium plate was prepared using 0.2 mol of sodium tetraborate and 0.07 mol Was pre-washed in a solution containing sodium pyrophosphate. Next, this is 4.9% Ammonia (NH_ThreeAnd 0.2 mole of diammonium hydrogen phosphate Peak voltage of 400 dc volts and 200 amps / m in electrolyte containing^TwoNo ba Anodized at lux current density. After reaching 400 volts (in just 7 minutes) The power was turned off and a 9 μm anode film was observed on the sample. The total cycle time is 7 minutes. Example 2   AM50 magnesium parts up to 350 DC volts endpoint voltage 0 amps / m^TwoAnodized. 3% electrolyte composition Ammonia (converted to the weight of ammonia gas) and 0.2 mol of hydrogen phosphate diammonium Was nickel. This part was cleaned before anodization, but other pretreatments were performed. I didn't know. After reaching the endpoint voltage, the power to the sample is maintained and 35 Maintained at 0 VDC for about 10 minutes. When the sample is washed, the anode It was found to have a membrane. Example 3   The AZ91D magnesium plate is treated with 8% ammonia (weight of ammonia gas). Anodic oxidation in an electrolyte containing 0.1 mol of phosphoric acid. This sample Containing 0.2 mol of sodium tetraborate and 0.07 mol of sodium pyrophosphate Pre-wash in a bath for 5 minutes and then 35% hydrofluoric acid (% by volume) before anodic oxidation ) In a bath containing 200 amps using a 465 volt DC power supply A / m^TwoWas maintained for 5 minutes to perform anodization. 21.8 μm coating obtained Was done. The anodization cycle required a total of 26 minutes. Example 4   AZ91D magnesium plate with 5% ammonia (converted to ammonia gas weight) ), An anode in an electrolyte containing 0.1 mol of phosphoric acid and 0.03 mol of hydrogen peroxide Oxidized. This plate was pre-cleaned as in Example 3 above and then as in Example 3 above. Activated. Then a DC voltage reaching 385 volts and an alternating voltage reaching 52 volts Anodizing was performed using a power supply with a flowing voltage. DC current density is 280 Amps / m^Twoso, On the other hand, the alternating current density has a peak of 90 amps / m^TwoMet. DC end poi The sample voltage was maintained for 5 minutes and the sample was Pretreatment for 2 minutes in a bath containing sodium dihydrogenate. Anodizing cycle It took a total of 15 minutes. Example 5   An AZ91D test plate was prepared in the same manner as in Example 3 above by using 0.2 mol of sodium tetraborate. Pre-washed in a bath containing water and 0.07 mol of sodium pyrophosphate. 2.5 % Ammonia (converted to ammonia gas) and 0.5 mol of diethylenetriamine (DEA) and an electrolyte containing 0.1 mole of phosphoric acid, rated at 360 volts positive Extremely oxidized and maintained for 5 minutes. Current density is 200 amps / m^Two Met. This plate was observed to have a 28.2 μm anode coating . The total cycle time was 21 minutes for the anodization process. Example 6   The AZ91D test plate was pre-washed in this mixture as described in Example 3 (activated Not in). Then 19.8% by weight molar ethanolamine and 0.2 mol phosphorus Anodizing with a DC power supply rated at 350 volts in a solution containing sodium dihydrogen acid, It was maintained for 5 minutes. Current density is 200 amps / m^TwoMet. This board is 2 It was observed to have a 0.2 μm anode coating. Total cycle time Was 16 minutes 30 seconds for the anodization process.   In the above example, the process time represents the anodizing time, and the pre-cleaning and Does not include post-treatment of activation or anodic oxidation.

[Procedure for Amendment] Article 184-8, Paragraph 1 of the Patent Act [Date of Submission] December 18, 1998 (Dec. 18, 1998) [Details of Amendment] Claims 1. Immersing magnesium or a magnesium alloy as an anode in an electrolyte, providing a cathode in the electrolyte, and passing an electric current through the electrolyte; or a method of anodizing magnesium or a magnesium alloy, The electrolyte has a pH of greater than 7 and contains, in water, (1) ammonia or an amine or a mixture of the two, and (2) phosphoric acid or a water-soluble phosphate, provided that at least Anodizing magnesium or magnesium alloy comprising or consisting of: 2. The method of claim 1 wherein the ammonia is present at a concentration of 0.4 to 12 molar. 3. The method according to claim 1 or 2, wherein (2) is provided as phosphoric acid, and the phosphoric acid is provided in a range of 0.05 to 0.2 mol. 4. 4. The method according to claim 1, wherein the electrolyte comprises a blowing agent. 5. The method according to any one of claims 1 to 4, wherein the electrolyte comprises a water-soluble peroxide. 6. The amine is used alone in step (1) or in combination with ammonia in step (1), wherein the amine is a water-soluble primary, secondary or tertiary amine having a pKa greater than 5. The method described in. 7. 7. The method according to any one of claims 1 to 6, wherein the amine has a pKa greater than 9. 8. The method according to any of the preceding claims, wherein the magnesium or magnesium alloy article is cleaned by a pre-treatment step before anodizing. 9. The pre-treatment step comprises: (A) immersing the article in a 70-90 ° C. solution of a mixture of sodium tetraborate and sodium pyrophosphate for at least about 5 minutes; (B) 35% by volume hydrofluoric acid at ambient temperature. Immersing the article for about at least 1 minute, or (C) immersing the article in a 1: 1 mixture of 35% by weight hydrofluoric acid and 68% by weight nitric acid for about at least 1 minute. The method of claim 8, comprising: 10. The material may be (I) (a) (1) a DC voltage of 300 volts or more (if the electrolyte contains ammonia and no amine), or (2) a DC voltage of 250 volts or more (when the electrolyte is amine or ammonia (Including amines), and (b) if desired, (1) typically 0 to 40 volts, optionally higher AC voltage, (2) typically 0 to 40 volts, optionally higher pulse voltage (square wave) , and (II) 50 to 1000 a current density of amps / m ^2, is an anode with a current having a characteristic oxidation method according to any one of claims 1-9.

────────────────────────────────────────────────── ─── Continuation of front page    (31) Priority claim number 328719 (32) Priority date September 11, 1997 (September 11, 1997) (33) Priority country New Zealand (NZ) (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, L U, MC, NL, PT, SE), OA (BF, BJ, CF) , CG, CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, M W, SD, SZ, UG, ZW), EA (AM, AZ, BY) , KG, KZ, MD, RU, TJ, TM), AL, AM , AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, E S, FI, GB, GE, GH, GM, GW, HU, ID , IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, M G, MK, MN, MW, MX, NO, NZ, PL, PT , RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, V N, YU, ZW (72) Inventors Henschau, Joffrey Stephen             New Zealand, Auckland, Remi             Juela, Victoria Avenue 3/153

Claims (1)

[Claims] 1. Immersing magnesium or a magnesium alloy as an anode in an electrolyte, providing a cathode in the electrolyte, and passing an electric current through the electrolyte, comprising: or an anodic oxidation of magnesium or magnesium alloy, The electrolyte has a pH greater than 7 and comprises or consists of in water the following: (1) ammonia or an amine or a mixture of the two, and (2) phosphoric acid or a water-soluble phosphate. Anodizing method for magnesium alloy. 1. The method of claim 1 wherein the ammonia is present at a concentration of 0.4 to 12 molar. 2. The method according to claim 1 or 2, wherein (2) is provided as phosphoric acid, and the phosphoric acid is provided in a range of 0.05 to 0.2 mol. 4. 4. The method according to claim 1, wherein the electrolyte comprises a blowing agent. 5. The method according to any one of claims 1 to 4, wherein the electrolyte comprises a water-soluble peroxide. 6. The amine is used alone in step (1) or in combination with ammonia in step (1), wherein the amine is a water-soluble primary, secondary or tertiary amine having a pKa greater than 5. The method described in. 7. 7. The method according to any one of claims 1 to 6, wherein the amine has a pKa greater than 9. 8. The method according to any of the preceding claims, wherein the magnesium or magnesium alloy article is cleaned by a pre-treatment step before anodizing. 9. The pre-treatment step comprises: (A) immersing the article in a 70-90 ° C. solution of a mixture of sodium tetraborate and sodium pyrophosphate for at least about 5 minutes; (B) 35% by volume hydrofluoric acid at ambient temperature. Immersing the article for at least about 1 minute, or (C) immersing the article in a 1: 1 mixture of 35% by weight hydrofluoric acid and 68% by weight nitric acid for at least about 1 minute. Item 9. The method according to Item 8. 10. The material may be (I) (a) (1) a DC voltage of 300 volts or more (if the electrolyte contains ammonia and no amine), or (2) a DC voltage of 250 volts or more (when the electrolyte is amine or ammonia (Including amines), and (b) if desired, (1) typically 0 to 40 volts, optionally higher AC voltage, (2) typically 0 to 40 volts, optionally higher pulse voltage (square wave) , and (II) 50 to 1000 a current density of amps / m ^2, is an anode with a current having a characteristic oxidation method according to any one of claims 1-9. 11. The method of claim 10 the current density is 200 to 350 Amps / m ^2. 12. A method of anodizing magnesium or a magnesium alloy (hereinafter referred to as “magnesium material”) by providing an electrolyte solution, providing a cathode in the solution, and using magnesium as a main component in the solution as an anode. Disposing a material and passing an electric current between the anode and the cathode through the anode to form an anodized surface, wherein the electrolyte has a pH greater than 7. (a) (1) ammonia and amine or (2) amine, and (b) (1) at least one source of phosphate ion and / or (2) at least one source of aluminate anion and fluoride Wherein at least one source of ions comprises or consists of in water, wherein the current applied during the anodization comprises: (A) (1) hydrogen peroxide and / or soluble peroxide If not in solution Greater than 20 volts, (2) greater than 210 volts if hydrogen peroxide and / or soluble peroxide is not present in the electrolyte solution, (B) providing a significant degree of sparking on the magnesium material, or anode And / or its anodized surface as a plasma discharge is higher than would otherwise be possible without giving a significant degree of sparking on the magnesium material, or its anodized surface and / or plasma discharge is present in the electrolyte anode Not for ammonia and / or amine, but in each case below the voltage limit. Anodizing method for magnesium material. 13. 13. The method of claim 12, wherein the amine can be present in ammonia gas or an alkaline solution of a volatile amine component. 14． 14. The method according to claim 12 or 13, wherein the electrolyte solution comprises at least one source of phosphate ions. 15. 15. The method of claim 14, wherein a source of phosphate ions is present and no optional aluminate and fluoride ions are present. 16. The method according to claim 12, wherein the anodization is performed when the electrolyte solution is below 50 ° C. 17． 13. The method according to claim 12, wherein the voltage limit is above 300 volts and below 600 volts for (A) (1), and above 280 volts and preferably below 550 volts for (A) (2). . 18. The method according to claim 12, wherein the aqueous electrolyte solution contains at least 3% by weight of ammonia (converted to ammonia gas). 19. 19. The method according to claim 18, wherein the aqueous electrolyte solution contains at least 5% by weight or more of ammonia (converted to ammonia gas). 20. 20. The method of claim 19, wherein the at least one source of phosphate ions is selected from the group of phosphoric acid, soluble phosphate, and soluble ammonium phosphate. 21. 15. The method of claim 14, wherein the phosphate ions are obtained by adding phosphoric acid to the bath, thereby producing various phosphate anions by hydrolysis. 22. The method of claim 14, wherein the phosphate ion source is present in the range of 0.01 to 0.2 mol. 23. 15. The method of claim 14, wherein the source of phosphate ions is present in the range of about 0.05 to 0.15 mole. 24. 13. The method according to claim 12, wherein hydrogen peroxide or soluble peroxide is present. 25. The method of claim 1, wherein the electrolyte solution further comprises at least one of the group consisting of aluminates, silicates, borates, fluorides, phosphates, citrates, and phenols. 26. 13. The method of claim 12, wherein the electrolyte anodization does not include significant presence of chromium (III) and chromium (VI). 27. 13. The method according to claim 12, wherein the electrolyte solution does not include an alkali salt that produces hydroxyl ions by hydrolysis. 28. A method for anodizing a magnesium-based material (ie, magnesium or a magnesium alloy), comprising: providing an electrolyte solution having a pH greater than 7, comprising: (a) (1) ammonia and an amine or (2) an amine, and (b) at least one source of (1) phosphate ions, and / or (2) at least one source of aluminate anions and at least one source of fluoride ions, Providing a cathode to the solution, disposing a magnesium-based material in the solution as an anode, and passing a current between the anode and the cathode through the anode to form a cathode of the material. Forming an anodized surface thereon, wherein the ammonium and / or amine in the electrolyte solution causes a partial melting or melting of the anodized surface layer during the anodization process. Wherein the electrolyte solution comprises or consists of water and a source of phosphate ions provided in the range of 0.1 to 0.2 moles. Wherein a source of the phosphate ions is selected from the group consisting of phosphoric acid and a soluble phosphate; a method of anodizing a material containing magnesium as a main component. 29. 29. The method of claim 28, wherein the ammonia is at least 1% by weight of the electrolyte solution in terms of gas. 30. An anodizing method of magnesium or a magnesium alloy comprising or comprising operating an anodizing system of a magnesium or magnesium alloy material as an electrolyte solution, a cathode, and an anode, wherein the electrolyte solution comprises: Or (2) (a) one or more amines and (b) ammonia in solution, under electrical input conditions excluding the introduction of amine and ammonia in solution. A method of anodizing magnesium or magnesium alloy that does not produce a tight anodized coating. 31. 31. A magnesium or magnesium alloy article anodized by the method of any one of claims 1-30.