TWI248480B - Method for producing corrosion protective coatings on light metal alloys - Google Patents

Abstract

A corrosion-prevention surface treating method for light metals especially of aluminum and magnesium alloys. In electrolytes containing alkaline hydroxides and alkaline silicates, through application of positive and reverse pulse DC current, a uniform and corrosion resistant coating can be formed on the surface of the treated alloys. The ratio between pulse duration and rest interval between pulses are important process parameters. The ratio of pulse duration and rest period is to be maintained between 1:3 and 1:10. The time intervals between pulse and reverse pulse are kept between 0.3 and 30 millisecond. Every three and twelve pulses are to be followed by a single action of reverse pulse. This surface treatment is applicable on forged and die casted light metal alloys or metallic components of complex shapes. For high silicon (up to 12%) containing aluminum alloys is also a suitable candidate with a resulting surface coatings encompassing high concentration of oxidized substrate materials and minor presence of silicon oxides.

Description

1248480 Case No. 92128941 A_Μ. 修正 Amendment V. Description of the Invention (1) [Technical Field of the Invention] The present invention is a surface treatment method which makes electric light metal sheets resistant to money. [Prior Art] Recently, there are a large number of light-shell and electrical devices that have not been used for the following reasons compared to conventional materials. In 1970, the electric valve used in metal valve was attempted to change, including the coating of micro-plasma oxidation and arc plasma discharge, the formation of micro-mineral layer and the potential difference between the two sides of the light metal surface of the micro-arc plasma. Regarding the alloys (the parts of these factors affect the process of the generation of intermediate surface applications for the inclusion of glow electrolysis (not arc electrodeposition peroxide to an electric booster, Markov oxide oxide commercialization. Electroplating, glow plasma oxidation. The process of oxidation of the glow discharge slurry involves the influence of the current in the shape of the critical voltage. The glow-discharge micro-arc oxidation technique has undergone multiple micro-arc oxidation, which appears to be due to the micro-generation of a good technique. The chemical reaction is In the field of surgery, an invention relating to the manufacture of an anti-corrosion coating on a light metal surface is formed by a pulsed direct current on a light metal surface to form a homogeneous, resist-plated coating, thereby improving the light gold micro-arc oxidation. Proposed, in particular, articles made of magnesium and aluminum, such as outer, structural and consumable components, micro-electric Oxidation anti-corrosion treatment. While micro-arc oxidation should be limited, such as: increased power consumption, higher roughness coating, electrolyte containing harmful and Hradcovsky protective layer, the name of this technology is photo-discharge oxidation, standing on the sidelines Role or arc discharge) The name best represents the plasma chemistry and plasma chemical reaction machine into a dielectric layer, and the dielectric layer eventually leads to a certain area in the dielectric layer.

1248480 --- Case No. 92128941_年月曰曰 ___ V. Invention Description ^一~^ " The domain first collapses, produces ionization phenomenon, generates an active substance, which forms an electricity in the dielectric layer The slurry pipeline begins to discharge, and the dielectric layer has a dielectric breakdown in the region with a lower dielectric constant, and other regions in the dielectric layer are caused by the next pulse current, and the discharge reaction position shifts, causing dielectric breakdown. This will result in a continuous plasma reaction of the entire surface of the object being processed. Finally, the plasma chemical reaction produces a uniform dense oxide layer on the surface of the metal being treated. In U.S. Patent Nos. 3,959,080 and 4,082,262, Hradcovsky discloses a technique for applying a layer of a silicate layer to the surface of a metal valve. The technique uses a continuous direct current, in the presence of an alkali metal citrate. The salt is combined with an electrolyte of an alkali metal hydroxide and a catalyst such as a naphthenate (U.S. Patent No. 3,956,080) or a metal peroxide (U.S. Patent No. 4,082,262). The voltage range of this reaction is 22 0V to 150 〇 V, and the current density is 0 · 5 to 1 0 · 0 A / d in2. Using a continuous direct current, the reaction finally produces a tantalate coating.

In the US patent brother 5811194 5, Kurze unveiled the method of regenerating into a layer of 4 〇-150/zm oxidized ceramic coating on a metal surface containing an insulating layer. The method uses a direct current or an alternating current as a power source, and contains an electrolyte containing a phosphate, a borate, and a fluoride. Further, a stabilizer is added, and the stabilizer is selected from the group consisting of hexamethylenediamine, urea, ethyl alcohol, and glycerin. The operating temperature is -3 °C to 15 °C and the operating temperature must be maintained at plus or minus 2 °C. The current density is 1 A / dm2 and the voltage is 50 to 400 V. This reaction is carried out in a fixed current mode. The main disadvantage of this method is that it contains harmful substances in the electrolyte and the reaction must be carried out in a low temperature environment with a limited temperature range.

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Case No. 92128941 V. INSTRUCTIONS (3) In US No. 6365028, the proposed solution for the two problems of Kurze mentioned above, Shatrov generates a hard protective coating on the surface of the aluminum alloy article. The invention uses 50 to 60 Hz alternating current as the The power source contains an alkali metal hydroxide, an alkali metal silicate, an alkali metal coke salt and a peroxide. The reaction is divided into two stages, in which the reaction is carried out for a period of 5-90 seconds at a current density of 160 to 180 A/dm 2 ; in the second step 1, the current density is decreased to 3 to 30 A/dm 2 , and the reaction is continued and $ Its & required power continues to decrease 'until a plating of the necessary thickness is generated, the electrolyte of this reaction does not contain harmful substances, and can be carried out at room temperature (15 to 5 但 but because of the 咼 current, the degree High power consumption, and high roughness coating due to use, and ancient. ^ ^ [Summary of the Invention] The main object of the present invention is to provide a surface coating on a light metal surface to avoid corrosion of light metal surfaces by external substances. The purpose is to reduce the smoothness of the power demineralization layer of micro-arc oxidation. '^Improve the invention mainly by using a forward/reverse surface to generate the arc electric device. In the forward pulse DC == light metal surface first forms a The dielectric layer, and the two sides of the 'breaking surface charge, when the pulsed DC voltage: 1 at both ends contains a number of surface dielectric layers, the region because of its dielectric coefficient; 7; = ' will make the phenomenon, Causing micro-electricity Plasma generation 'the arc 杈 early dielectric breakdown oxidized to oxide coating, while the reverse pulse i:: material surface melt and (such as hardness, porosity and smoothness). Volume; improve the properties of the coating The field reverse pulse is at the same time

1248480 Case No. 92128941 A_η Correction V. INSTRUCTIONS (4) When a micro-arc plasma is generated on the surface of the workpiece, no new oxide is formed. When the reverse pulse current is applied, the presence of the metal cation will cause the coating to be purified, so that it is undesirable to have an element that is easily melted in the ore layer, and this can be avoided by the reverse pulse current. Moreover, the reverse pulse current also improves the wear resistance of the coating. The invention mainly comprises completely immersing the object to be treated in a stainless steel electrolytic cell filled with an electrolyte and connecting with an anode, the electrolyte component comprising a metal hydroxide and a metal oxide, and a pulsed direct current as a The source of electricity, and each three to twelve times of forward pulse voltage will be accompanied by a reverse pulse voltage, a better quality coating can be obtained. The preferred embodiment and technical contents of the present invention are as follows: [Embodiment] First Embodiment 1. First, a forged aluminum alloy 6 0 6 1 is taken as the object to be processed 6. 2. Prepare an electrolytic cell 4 to prepare an electrolyte 5 in which the electrolyte 5 contains 10 g/L of sodium hydroxide 1 5 g / L sodium citrate 3. The object to be treated is connected to the anode 8 1 and the cathode 8 2 is placed in a stainless steel. Operation of the chip 4. Using forward pulse DC as the power supply 8, the parameters of the reaction for 10 minutes are as follows: Forward pulse time 1: 1. 0 ms Forward pulse interval time 3: 3. Oms

Page 10 1248480 __ Case No. 92128941 V. Description of invention (5) Current density: 5A/dm2 Yearly 曰 Correction

5 · The reaction produces a smooth, dense 'homogeneous 8 // m thick resist money show. The second embodiment transports 60. 1. First, a die-cast aluminum alloy ADC 12 is taken as the object to be processed 6. 2. Preparing an electrolytic cell 4 to prepare an electrolyte 5 in which the electrolyte 5 contains 8 g/L of sodium hydroxide and 18 g / L of sodium citrate. 3. The object to be treated 6 is connected to the anode 81, and the cathode 82 is placed in a non-mine. Steel plate 7 〇' 4 · Use forward/reverse pulse DC as power supply 8 and react for 分钟5 minutes. The operating parameters are as follows: Forward pulse time 1 ·· 1. 〇ms Reverse pulse time 2 ·· 1. 〇 Ms Forward/reverse pulse interval time 3 1 : 4 · 〇ms Current density: 5 A / dm 2 5 · The reaction produces a smooth, dense, homogeneous 8 // m thick wear resistance and better resistance to the clock layer 6 0. Example 3 of the soil brother 3 1. First, a die-cast magnesium alloy AZ91D is taken as the object to be processed 6. 2. Preparing an electrolytic cell 4 to prepare an electrolyte 5 in which the electrolyte 5 contains 10 g/L of sodium hydroxide 20 g/L of sodium citrate. 3. The object to be treated 6 is connected to the anode 81, and the cathode 82 is placed with a stainless steel piece.

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, reaction 1 5 minutes, its operation _ case number 92128941 month five, invention description (6) 4. using forward pulse DC as the power supply 8 parameters are as follows: forward pulse time 1: 0. 5 ms forward pulse interval time 2 : 2. Oms current density: 2. 5A / dm2 5 · The reaction produces a smooth 8 / 4 m thick containing magnesium oxide, aluminum oxide and oxygen anti-surname plating 60. Example 4: First, a die-cast magnesium alloy AZ9 1 D is taken as the object to be processed 6. 2. Preparing an electrolytic cell 4 to prepare an electrolyte 5 in which 8 g/L of sodium hydroxide in the electrolyte 5 is < 2 5 g / L sodium citrate 3 · The object to be treated 6 is connected to the anode 8 1 , and the cathode 8 2 Place a non-ferrous steel sheet 1 ° 4 · Use forward/reverse pulse DC as the power supply 8 and react for 分钟 5 minutes. The operating parameters are as follows: Forward pulse time 1: 〇. 5 ms Reverse pulse time 2 : 0 . 5 ms forward/reverse pulse interval time 3 1 : 2 . 5ms Current density: 3.0 A/dm2 5 · The reaction produces a smooth, dense 1 〇 thick anti-corrosion coating 60. Fifth Embodiment! First, a forged magnesium alloy AZ31 was taken as the object to be processed 6. 2. Preparing an electrolytic cell 4 to prepare an electrolyte 5 in which the electrolyte 5 contains

Page 12 1248480 Case No. 92128941 Revised Month 5, invention description (7) l〇g / L sodium hydroxide 2 0 g / L sodium citrate 3. The object to be treated 6 is connected to the anode 81, the cathode 82 is placed a stainless steel Ί 〇 4. Use forward pulse DC as the power supply 8 and react for 15 minutes. The operating parameters are as follows: Forward pulse time 1: 0 . 5 in s Forward pulse interval time 2 : 2 · 5 ms Current density: 2.0 A/dm2 5. The reaction produces a smooth, 1 5 // m thick anti-key layer 60. The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. That is, equivalent changes and modifications constituting the scope of the patent application of the present invention should be the technical scope of the present invention.

Page 13 1248480 Case No. 92128941 Yearly correction diagram simple description [Simple diagram of the diagram] Figure 1, reaction current and time diagram Figure 2, schematic diagram of the embodiment of the invention 3 diagram 'after the article is processed Section view [schematic description] 1 ....... forward pulse time 2 .... reverse pulse time 3 ... ... forward pulse interval time 3 .... ... forward/reverse pulse interval time 4 ... electrolytic cell 5 ... electrolyte 6 ... ... treated object 6 0 ... mineral layer 7 .......Do not record steel sheets 8 .......Power supply 81...Anode 8 2...Cathode

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Claims (1)

1248480 Case No. 92128941 Revised on the sixth day of the month. Patent application scope 1. A light metal alloy anti-money plating surface treatment method characterized in that a micro-plasma arc is used to generate a primary coating on a light metal surface, the steps of which include: Taking a light metal alloy to be treated; (2) placing the light metal alloy to be treated into an electrolyte containing 5-25 g/L of metal hydroxide and 15-50 g/L of alkali metal silicate (3) connecting the light metal alloy to be treated to the anode; (4) placing a stainless steel piece on the cathode; (5) passing a pulsed direct current with a current density of 1 - 1 0 A / dm 2 'the pulse time and the pulse interval time The ratio is 1: 3 to 1: 1 0, the pulse time is 0. 1 to 3. 0 ms, the pulse interval is 0.3 to 30 ms, and the total reaction time is 3 - 60 minutes. 2. The surface treatment method of the light metal alloy anti-Im coating according to the first aspect of the patent application, wherein the light metal alloy is a Ming or a town alloy. 3. The surface treatment method of the light metal alloy resist coating according to claim 1, wherein the light metal alloy is an alloy of high stone content. 4. The light metal alloy anti-I pest coating surface treatment method according to claim 1, wherein the pulsed direct current is a forward or reverse pulse direct current. 5. The surface treatment method of a light metal alloy resist coating as described in claim 4, wherein after every 3 to 12 times of forward pulse direct current, a reverse pulse direct current action is applied. 6. The light metal alloy anti-I pest coating surface treatment method according to claim 1, wherein the alkali metal hydroxide is sodium hydroxide hydrated potassium hydroxide. 7. The method of surface treatment of a light metal alloy anti-residue layer according to claim 4, wherein the alkali metal silicate is sodium citrate. Page 15