JP2004346407A - Methods and apparatuses for surface-treating and plating aluminum alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably reduce an amount of treated waste water and simultaneously a purchase cost for chemicals, in a method for surface-treating an aluminum alloy before plating. <P>SOLUTION: The method for surface-treating the aluminum alloy comprises: the step of electrolytically etching the aluminum alloy with the use of an acid solution; the step of anodizing the electrolytically etched aluminum alloy with the use of the solution including the same acid used in the electrolytic etching step; the step 70 of recovering the acid from the spent acid solution 71 produced in the electrolytic etching step; the step of reusing the recovered acid 73 in the electrolytic etching step; and the step of using a liquid 74 left after the acid has been recovered from the spent acid solution, in the anodizing step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface treatment method and a plating method for an aluminum alloy, and a surface treatment facility and a plating facility for an aluminum alloy, and more particularly, to a method for recovering an acid from a plating acid solution used in an electrolytic etching process and recycling the acid.
[0002]
[Prior art]
As a method of plating an aluminum alloy that is shorter, simpler, and has higher plating adhesion than the zinc substitution method and the anodic oxidation method, an aluminum alloy containing silicon is subjected to anodic electrolytic etching, and from the surface of the aluminum alloy, There is known an aluminum alloy plating method including a step of projecting silicon and a plating step (Patent Document 1). Further, in this plating method, after the anodic electrolytic etching, the aluminum alloy portion can be made porous by forming an anodic oxide film on the aluminum alloy portion other than the silicon crystal on the work surface. By performing plating after anodic oxidation in this way, a silicon film bridged between the aluminum alloy and the plating layer, the unevenness of the work surface, and the porosity generated by anodic oxidation form a highly adherent plating film. Can be done. By the plating method according to Patent Document 1, excellent adhesion to an aluminum alloy having an arbitrary silicon concentration can be obtained.
[0003]
In the above plating method, an acid solution (such as phosphoric acid) is used as an electrolytic solution in the electrolytic etching step and the anodic oxidation step, and the aluminum component elutes from the work into the acid solution as the number of treatments increases. In each process, a defect such as an abnormal voltage or poor powder blowing may occur. In order to prevent this, it is necessary to periodically renew the acid solution, which is a treatment liquid, and there are problems such as an increase in the cost of the chemical solution and an increase in the amount of wastewater treatment.
[0004]
According to Patent Literature 2, for an acid treatment solution contaminated with aluminum, in the case of a hydrochloric acid waste solution, a method of neutralizing and discarding, or a concentrated aluminum chloride solution obtained by concentration treatment is used as a papermaking flocculant. The technology is known. For sulfuric acid waste liquid, an acid recovery technique by a diffusion dialysis method is known (see Patent Document 3). Further, with respect to nitric acid waste liquid, a technique for separating aluminum as a pollutant using an ion exchange resin is known.
[0005]
These methods have problems such as the cost of chemicals used for the neutralization treatment, the cost of the heat source for the concentration treatment, and the cost of renewing the ion exchange resin, and there is no inexpensive and direct method for recycling the acid. In addition, although the operation cost of the diffusion dialysis method is very low, there is a problem that an acid solution having a concentration lower than that of a stock solution can be obtained because an acid is recovered by utilizing a concentration difference of an acid in the solution. Furthermore, the residual acid after dialysis is discarded because it has no use, and there is a problem that the total amount of waste liquid cannot be significantly reduced. As a countermeasure, there is an electrodialysis method (see Patent Literature 4). However, since power supply equipment is required, there is still a problem that the processing cost is high.
[0006]
[Patent Document 1]
JP-A-11-1795
[Patent Document 2]
JP-A-11-79739
[Patent Document 3]
JP-A-8-71377
[Patent Document 4]
JP-A-8-144100
[0007]
[Problems to be solved by the invention]
The present invention can significantly reduce the amount of wastewater treatment in the surface treatment of aluminum alloy before plating, and at the same time can significantly reduce the purchase cost of chemicals. The purpose is to provide equipment and plating equipment.
[0008]
[Means for Solving the Problems]
According to one aspect of the present invention, a step of electrolytically etching an aluminum alloy using an acid solution and anodizing the electrolytically etched aluminum alloy using a solution containing the same acid as the electrolytic etching step Recovering the acid from the used acid solution generated in the electrolytic etching step, reusing the recovered acid in the electrolytic etching step, and recovering the acid from the used acid solution. Using the remaining solution in the anodizing step. According to another aspect of the present invention, there is provided a method of plating an aluminum alloy, the method including a method of surface treating the aluminum alloy, and further including a step of plating the surface-treated aluminum alloy.
According to another aspect of the present invention, there is provided an electrolytic etching bath for electrolytically etching an aluminum alloy using an acid solution, and an electrolytically etched aluminum using a solution containing the same acid as the electrolytic etching. An anodizing bath for anodizing the alloy; an acid recovering device for recovering an acid from a used acid solution generated from the electrolytic etching bath; and an acid recovering the acid recovered by the acid recovering device. There is provided an aluminum alloy surface treatment facility comprising: means for supplying an acid to an etching tank; and means for recovering an acid from the used acid solution and supplying a remaining liquid to the anodizing tank. According to another aspect of the present invention, there is provided an aluminum alloy plating treatment facility including the aluminum alloy surface treatment facility, and further including a plating tank for plating the surface-treated aluminum alloy.
[0009]
In the present invention, as a plating pretreatment when plating an aluminum alloy work such as a cylinder, in a surface treatment step using electrolytic etching and anodizing, from a used acid solution generated from the electrolytic etching step, preferably The acid is recovered by diffusion dialysis and reused, and the acid generated by the recovery of the acid is recycled to the anodizing step. According to the present invention, only an acid component (such as phosphoric acid) is recovered in pure water from a used acid solution (waste acid) in an electrolytic etching process which has been previously discarded or drained, and the recovered acid is recovered. Can be reused in the electrolytic etching step. In addition, when performing diffusion dialysis, the residual acid (dilute acid aqueous solution containing impurities such as aluminum) generated by the diffusion dialysis is generally discarded. However, a solution containing the same acid is used for the electrolytic etching treatment and the anodic oxidation treatment, and in the plating pretreatment of the present invention, which preferably has a different acid concentration, the residual acid is anodized. Can be reused in the process. As described above, according to the present invention, the cost of disposal can be reduced, and the cost of purchasing chemicals can be significantly reduced.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the accompanying drawings. However, the following embodiments according to the present invention do not limit the present invention.
In the present embodiment, the target work is carried to the plating line after the completion of the machining. The target workpiece is degreased to remove cutting oil, electrolytic etching, and then anodizing plating pretreatment, and then Ni-P-SiC dispersed plating for imparting wear resistance. High speed plating is performed.
[0011]
Examples of the aluminum alloy used in the present invention include an ADC material, an AC material, and a wrought material. More specifically, there may be mentioned JIS standard AC4C, AC4B, AC4D, AC8A, ADC10, ADC12 and the like.
[0012]
The method of the present invention can be carried out in the order of, for example, degreasing, washing with water, anodic electrolytic etching, washing with water, anodizing treatment, washing with water and plating.
[0013]
The degreasing is preferably performed at a temperature of 40 to 50 ° C. for 3 to 30 minutes using a degreasing agent such as NG30 (manufactured by Kizai). The anodic electrolytic etching is preferably performed by immersing an aluminum alloy containing silicon in an electrolytic solution, using the aluminum alloy as an anode, using an insoluble electrode as a cathode, and supplying electricity in an electrolytic solution containing an acid. By this treatment, the aluminum component in the silicon-containing aluminum alloy dissolves, so that silicon projects on the surface of the aluminum alloy and irregularities are formed on the surface of the aluminum alloy.
[0014]
Here, as the electrolytic solution, for example, a solution containing an acid such as phosphoric acid, sulfuric acid, hydrochloric acid, sulfamic acid, and oxalic acid can be used. When phosphoric acid is used as the electrolytic solution, a concentration of 40 to 900 g / L (more preferably 200 to 400 g / L), a temperature of 50 to 100 ° C (more preferably 60 to 85 ° C), and 20 to 400 A / dm.²(More preferably 30 to 100 A / dm²It is preferable to carry out electrolytic etching at the anode current density of (a). When the concentration is less than 40 g / L, aluminum does not dissolve, silicon is insufficiently deposited, and a sufficient anchor effect cannot be obtained, so that adhesion may be deteriorated. If the concentration exceeds 900 g / L, waste liquid treatment and handling may be difficult. If the temperature is lower than 50 ° C., since an anodic oxide film is formed on the surface of aluminum, the aluminum does not dissolve, the protrusion of silicon becomes insufficient, a sufficient anchor effect cannot be obtained, and the adhesion of the plating becomes poor. May worsen. If the temperature exceeds 100 ° C., the amount of evaporation is large, and frequent replenishment of the electrolyte is required, which is not preferable. Anode current density is 20A / dm²If the amount is less than the above, there is no etching effect, and the adhesion of the plating may be deteriorated. Anode current density is 400 A / dm²Exceeding the above is undesirable because a large amount of heat is generated and a cooling device is required.
[0015]
When sulfamic acid is used as the electrolyte, the concentration is 75 to 600 g / L, the temperature is 65 to 100 ° C, and the concentration is 50 to 300 A / dm.²Electrolytic etching is preferably performed at an anode current density of. When the concentration is less than 75 g / L, aluminum does not dissolve, so that silicon does not protrude, a sufficient anchor effect cannot be obtained, and adhesion of plating may be deteriorated. If the concentration exceeds 600 g / L, sulfamic acid is not dissolved and becomes saturated, which is not preferable. If the temperature is lower than 65 ° C., aluminum does not dissolve, the protrusion of silicon becomes insufficient, a sufficient anchor effect cannot be obtained, and the adhesion of plating may be deteriorated. If the temperature exceeds 100 ° C., the amount of evaporation increases, and frequent replenishment of the electrolyte is required, which is not preferable. Anode current density is 50A / dm²If it is less than 1, aluminum may not be dissolved, and an anchor effect due to precipitation of silicon may not be obtained. Anode current density is 300A / dm²Exceeding the above is undesirable because a large amount of heat is generated and a cooling device is required. When a nickel sulfamate solution is used as the plating solution, washing with water after the pretreatment becomes unnecessary, and the process can be shortened.
[0016]
When sulfuric acid is used as the electrolyte, a concentration of 75 to 600 g / L, a temperature of 50 to 100 ° C., and 50 to 200 A / dm.²Electrolytic etching is preferably performed at an anode current density of. When the concentration is less than 75 g / L, an anodic oxide film is formed on the surface of aluminum, aluminum does not dissolve, an anchor effect due to protrusion of silicon cannot be obtained, and adhesion of plating may be deteriorated. If the concentration exceeds 600 g / L, it becomes difficult to treat and handle the waste liquid, which is not preferable. If the temperature is lower than 50 ° C., an anodic oxide film is formed on the aluminum surface, the aluminum is not dissolved, the anchor effect due to the protrusion of silicon is not obtained, and the adhesion of the plating may be deteriorated. If the temperature exceeds 100 ° C., the amount of evaporation increases, and frequent replenishment of the electrolyte is required, which is not preferable. Anode current density is 50A / dm²If it is less than 1, the aluminum does not dissolve, the anchor effect due to the protrusion of silicon cannot be obtained, and the adhesion of the plating may be deteriorated. Anode current density is 200 A / dm²Exceeding the above is undesirable because a large amount of heat is generated and a cooling device is required.
[0017]
When a mixed solution of phosphoric acid and sulfuric acid is used as the electrolytic solution, the concentration of phosphoric acid is 0 to 900 g / L, the concentration of sulfuric acid is 0 to 600 g / L, the temperature is 50 to 100 ° C., and the temperature is 50 to 300 A / dm.²Electrolytic etching is preferably performed at an anode current density of. There is no particular limitation on the mixing ratio of phosphoric acid and sulfuric acid. However, for example, when the mixing ratio of sulfuric acid is extremely small, the concentration of phosphoric acid needs to be at least about 40 g / L. The reason for limiting the temperature range and the reason for limiting the numerical range of the anode current density are the same as those in the case of only phosphoric acid or the case of only sulfuric acid.
[0018]
The use of a mixture of phosphoric acid and sulfuric acid has the following advantages. That is, when only phosphoric acid is used, heat is easily generated due to a large electric resistance, and it is difficult to control the temperature. When only sulfuric acid is used, the electrical resistance is small, but an anodic oxide film is easily formed. In this respect, the mixed solution of phosphoric acid and sulfuric acid has a lower electric resistance, a smaller amount of heat generation, and easier management of the liquid temperature than the case of using only phosphoric acid. Further, no anodic oxide film is formed, dissolution of aluminum is promoted, an anchor effect due to protrusion of silicon is easily obtained, and adhesion of plating is enhanced.
[0019]
The electrolysis time is preferably 2 to 15 minutes (usually about 2 to 5 minutes) using any of the above types of electrolytes. As the insoluble electrode, for example, SUS (SUS304 or the like), Pt, Ti, Ti-plated Pt, or the like can be used.
[0020]
Examples of the plating include Ni-P-SiC plating, Ni-P plating, Ni-SiC plating, and hard chrome plating. Among them, when plating a cylinder block, a Ni-P plating film to which phosphorus is added, a Ni-SiC plating film in which SiC is dispersed, and a Ni-P-SiC plating film are particularly preferable in terms of wear resistance. . The plating is usually performed in a plating bath at a pH of 3.5 to 4.5 and a temperature of 55 to 65 ° C. in a plating bath of 5 to 100 A / dm.²It is preferable to carry out by applying a current at a current density of 5 to 60 minutes. When plating is performed on the aluminum alloy after the anodic electrolytic etching treatment, a plating film (plating layer) having good adhesion can be obtained by the anchor effect of both protrusion of silicon and formation of irregularities on the aluminum alloy.
[0021]
In the plating method of the present invention, further, after anodic electrolytic etching, before plating, anodizing treatment is performed to form an anodized film on an aluminum alloy portion other than silicon crystals on the work surface, thereby making the aluminum alloy portion porous. I do. By performing plating after anodic oxidation, a plated film with high adhesion can be formed by the bridged silicon, the unevenness of the work surface, and the generated porosity. In the anodic oxidation treatment, as described in detail below, the same jig, equipment, and electrolyte as used in anodic electrolytic etching can be used.
[0022]
An example of a production line for a 4-cycle cylinder made of an aluminum alloy in which at least three pretreatment steps are degreasing, electrolytic etching, and anodizing treatment will be described with reference to FIG. This manufacturing line includes a cylinder machining line 23, a plating line 24, and a cylinder honing line 25. The aluminum alloy four-cycle cylinder is machined in a cylinder machining line 23 and then put into a plating line 24. In the plating line, first, oil such as cutting oil is removed in the degreasing tank 11, then washed in the washing tanks 12 and 13, and put into the electrolytic etching tank 14. After the electrolytic etching treatment, the substrate is washed with water in washing tanks 15 and 16 and then put into an anodizing tank 17. After the anodizing treatment, the plate is washed in the washing tanks 18 and 19, then plated in the plating tank 20, and further washed in the washing tanks 21 and 22. Thereafter, honing is performed on the cylinder honing line 25.
[0023]
In the present embodiment, the degreasing tank 11 and the washing tanks 12 and 13 are collectively referred to as degreasing means, and the electrolytic etching tank 14 and the washing tanks 15 and 16 are collectively referred to as electrolytic etching means and anodizing treatment is performed. The tank 17 and the washing tanks 18 and 19 are collectively referred to as anodizing treatment means, and the plating tank 20 and the washing tanks 21 and 22 are collectively referred to as plating means. In the line, the method of transporting the aluminum alloy compact (work) is not particularly limited and is arbitrary. For example, a workpiece can be conveyed while being gripped by a workpiece chuck that moves on a line along a rail.
[0024]
The anodic oxidation treatment can be performed using a solution containing the same acid as the electrolytic etching treatment, such as phosphoric acid, sulfuric acid, hydrochloric acid, sulfamic acid, and oxalic acid, as the electrolytic solution. Among them, phosphoric acid is preferably used. When phosphoric acid is used as the electrolytic solution, phosphoric acid is 30 to 500 g / L (more preferably 40 to 100 g / L), temperature is 10 to 70 ° C (more preferably 30 to 60 ° C), and current density is 2 to 40 A / dm.²(More preferably 5 to 50 A / dm²) For 1 to 15 minutes (usually about 1 to 5 minutes). Note that, as described above, it is preferable that the electrolytic solutions used in the electrolytic etching treatment and the anodic oxidation treatment have different acid concentrations. As will be described in detail below, the residual permeate remaining after collecting the acid by diffusion dialysis from the used acid solution generated in the electrolytic etching process can be efficiently used in the anodizing process, and As a more essential difference, electrolytic etching can be performed more efficiently when the acid concentration is higher. On the other hand, in the anodic oxidation treatment, it is more effective to use a treatment liquid having a low acid concentration and containing a small amount of aluminum, such as a residual liquid. This is because a high voltage can be applied while suppressing dissolution of the aluminum alloy, so that a favorable oxide film can be efficiently formed. In the electrolytic etching process and the anodizing process, if a solution containing the same acid as the electrolytic solution, for example, a phosphoric acid solution is used, the acid can be collected and reused by diffusion dialysis, and the water washing step after the electrolytic etching process can be performed. It can be omitted, the line is shortened, and the productivity is improved.
[0025]
FIG. 2 is a schematic view of a cross section of a plating-coated aluminum alloy obtained by the method of the present invention including a step of anodizing treatment. In FIG. 2, an oxide layer 32 of the aluminum alloy exists between the aluminum alloy 31 and the plating layer 33.
[0026]
FIG. 3 shows an example of an apparatus for electrolytically etching a cylinder. 3, an insulating plate 46, an electrode plate 47, an insulating plate 48, an electrode plate 49, a cylinder (work) 50, a packing 52, an upper jig are provided on a lower frame 41a of a frame 41 having a lower frame 41a and an upper frame 41b. 53 are arranged. A hole having the same diameter as the inner diameter of the cylinder is formed in the center of each of these members, and these centers are all arranged so as to be aligned on the same axis, thereby forming a liquid passage. These members are pressed down and fixed by the air cylinder 55 via the pressing rod 55a. The electrolyte is pumped from a liquid tank 42 by a pump 44, flows in from a liquid inflow portion 45 disposed below the lower frame 41a, passes through the inner surface of the cylinder, and is disposed in an upper jig 53. The liquid is discharged from the outflow portion 54 to the liquid tank 42. An electrode support 47a is provided at the center of the hole of the electrode plate 47, and the electrode 51 of the insoluble cathode (stainless steel round bar) is supported and fixed to the electrode support 47a so as to be located at the center of the passage of the electrolyte. . Normally, power is supplied from the power supply 43 with the electrode plate 47 being negative and the electrode plate 49 being positive so that the electrode 51 is negative and the cylinder (work) 50 is positive. The apparatus for performing the anodic oxidation treatment has almost the same structure as the electrolytic etching except that the treatment liquid is different.
[0027]
Further, in the present invention, since a solution containing the same acid, for example, a phosphoric acid solution is used for both the electrolytic etching process and the anodic oxidation process, the piping and the apparatus can be shared. Most of the reference numerals in FIG. 4 are the same as those in FIG. In FIG. 4, phosphoric acid for electrolytic etching is put in the liquid tank 42, and phosphoric acid for anodic oxidation is put in the liquid tank 42a, and they are sequentially flowed by the three-way valves 56a and 56b to be continuously processed. In this case, it is only necessary to switch the liquid while the cylinder, which is the work, is fixed, so that there is no need to transport the work, and the efficiency of a series of processing is high. In addition, since only one chuck is required, the risk of liquid leakage is reduced. The plating line in this case can be further shortened as shown in FIG. That is, as compared with FIG. 1, the water washing tanks 15 and 16 can be omitted, and the electrolytic etching tank 14 and the anodizing tank 17 can be shared by the same apparatus. The apparatus for plating the cylinder has almost the same structure as the electrolytic etching apparatus described above, except that the cylinder (work) 50 serves as a cathode, the electrode 51 serves as an anode, and the electrolytic solution is different, and is the same as that in FIG. is there.
[0028]
Here, as described above, when aluminum accumulates in the acid solution, symptoms such as an increase in liquid viscosity and an increase in voltage during electrolytic etching accompanying an increase in aluminum concentration appear, and problems such as powder blowing and burning occur. Is not preferred. Therefore, it is necessary to renew the processing solution for electrolytic etching with a target of about 20 g / L of aluminum concentration (more preferably, 10 g / L). Conventionally, an acid solution in which aluminum was dissolved was discarded. However, according to the present invention, only the acid was recovered from the used acid solution in which aluminum was dissolved using diffusion dialysis, so that the recovered acid was recovered again. It can be used in an electrolytic etching process. Furthermore, since the residual liquid remaining after collecting the acid from the used acid solution by diffusion dialysis can be recycled to the subsequent anodizing step, no waste liquid is generated.
[0029]
Diffusion dialysis involves, for example, undiluted solution on one side through an anion exchange membrane provided with a fixing group such as quaternary ammonium (which is called "diffusion dialysis membrane" because it selectively permeates only acid). When pure water flows to the other side, ions such as Fe, Al, Mn, and Co contained in the stock solution do not pass through the diffusion dialysis membrane due to repulsion of electric charge, and only the acid in the stock solution flows to the pure water side. This utilizes the phenomenon of transmission.
[0030]
FIG. 6 shows a schematic diagram of diffusion dialysis. In this example, aluminum sulfate [Al₂(SO₄)₃] And sulfuric acid (H₂SO₄), A recovered acid 63 containing only sulfuric acid, and a permeate 64 containing aluminum sulfate and diluted sulfuric acid (diffusion dialysis from waste acid). To recover the remaining acid). As shown in FIG. 6, in diffusion dialysis, a large number of sets of anion exchange membranes 60 designed for diffusion dialysis are laminated so as to provide a plurality of flow paths for waste acid 61 and pure water 62, and each of the laminated negative electrodes is formed. It is preferable to carry out the process by flowing waste acid 61 on one side of the ion exchange membrane 60 and water 62 on the opposite side. In this way, by flowing the waste acid 61 and the pure water 62 across the anion exchange membrane 60, the difference in the concentration of the acid generated through the anion exchange membrane 60 causes the waste acid 61 side to the water 62 side. The acid diffuses and moves to the (recovered acid 63 side), and the metal salt having a large polyvalent cation cannot pass through the anion exchange membrane and remains in the residual liquid 64. Thus, according to the diffusion dialysis, the free acid can be easily separated and recovered from the metal salt. It is preferable that the waste acid 61 is introduced from the lower part of the diffusion dialyzer and recovered from the upper part of the diffusion dialyzer as a residual liquid 64. Conversely, the water 62 is introduced from the upper part of the diffusion dialyzer and the recovered acid 63 is recovered. It is preferable to collect from the lower part of the diffusion dialysis device. This is because an acid can be more efficiently recovered by setting a solution having a higher specific gravity to a lower portion and a solution having a lower specific gravity to a higher portion.
[0031]
According to the present invention, an acid solution containing no aluminum is obtained as a recovered acid by diffusion dialysis. This recovered acid has a lower acid concentration than the concentration used for electrolytic etching. However, when the recovered acid is used in the electrolytic etching step, the solution is concentrated due to evaporation of water. Therefore, the recovered acid can be used without any problem as a treatment liquid for electrolytic etching. If necessary, a concentration tank may be provided for evaporating the recovered acid by heating the heater and concentrating the recovered acid. Alternatively, a high-concentration phosphoric acid solution may be added to the recovered acid so that the concentration of the acid in the solution is equal to the concentration of the acid in the treatment solution for electrolytic etching. As described above, according to the present invention, the used acid that has been conventionally discarded can be effectively used, so that the disposal cost can be reduced and the purchase cost of the acid chemical can be significantly reduced.
[0032]
Furthermore, the residual liquid generated by diffusion dialysis, that is, the liquid remaining after the acid is recovered from the used acid solution by diffusion dialysis, can be recycled in the next step of anodizing treatment. There is no need to prepare a processing solution of the above. For example, when phosphoric acid is used as the treatment liquid used in the anodic oxidation treatment, the concentration of phosphoric acid may be as thin as about 50 g / L. Therefore, the treatment liquid can be used by supplementing a small amount of phosphoric acid to the above-mentioned residual liquid. . In the anodic oxidation treatment, since the amount of electricity is low, problems such as powder blowing and burning are unlikely to occur, and the allowable range of the dissolved aluminum concentration is larger than that of electrolytic etching. It is. However, it is more preferable to perform the diffusion dialysis treatment in a state where the aluminum concentration in the electrolytic etching solution is as low as 10 g / L or less.
[0033]
In general, when anodizing an aluminum alloy, it is considered that a treatment liquid for anodization preferably has a state in which about several g / L of aluminum is dissolved. In a newly prepared treatment liquid, aluminum sulfate or aluminum sulfate is used. It is common to add a chemical such as aluminum phosphate. However, according to the present invention, the operation of introducing the above chemicals can be omitted by using the residual liquid obtained by diffusion dialysis of the waste acid. As described above, according to the present invention, it is not necessary to add an aluminum salt such as aluminum sulfate or aluminum phosphate even if a small amount of acid such as phosphoric acid is replenished for adjusting the concentration of the residual liquid. There are advantages. The waste liquid in the anodizing step is separately treated and discarded.
[0034]
Thus, according to the present invention, only the free acid can be separated and recovered from the waste acid containing the metal salt discharged from the metal surface treatment step, and the recovered acid can be reused in the surface treatment step and the like. , Acid can be used effectively. Further, as described above, the diffusion dialysis does not require a DC power for moving ions because the driving force is a difference in acid concentration in a solution. Therefore, the running cost is low, the apparatus is simple, and daily operation management is easy. Further, the diffusion dialysis membrane used in the present invention usually has a life of about 5 years, and the running cost is also low in this regard. The supply of the recovered acid to the electrolytic etching step, the supply of the residual liquid to the anodic oxidation step, and the treatment of the electrolytic etching waste liquid by diffusion dialysis can be performed in a batch process. It is possible.
[0035]
【Example】
An embodiment of the present invention will be described with reference to the drawings. FIG. 7 shows a schematic diagram of the plating step. That is, as a surface treatment before the plating treatment of the aluminum alloy, degreasing (including recovery cleaning and water washing), electrolytic etching (including recovery cleaning and water washing), and anodic oxidation (including recovery cleaning and water washing) were performed. As described in detail below, a used acid solution (used acid 71) generated in the electrolytic etching process and pure water 72 were introduced into a diffusion dialysis device 70, where diffusion dialysis was performed. The recovered acid 73 containing the recovered acid and the residual liquid 74 remaining after the acid was recovered from the spent acid 71 by diffusion dialysis were reused by electrolytic etching or anodic oxidation, respectively. The target work was an aluminum alloy cylinder, which was transported to the plating line after the completion of machining. After the cylinder is degreased to remove the cutting oil, it is subjected to electrolytic etching, followed by anodizing plating pretreatment, and then high-speed plating such as Ni-P-SiC dispersion plating for imparting wear resistance. Carried out.
[0036]
Alkaline degreasing was performed using a commercially available neutral degreasing agent (NG-30, manufactured by Kizai) at a concentration of 50 g / L, at a temperature of 50 ° C, and for a treatment time of 20 minutes. For the electrolytic etching, a phosphoric acid solution was used. Table 1 shows the electrolytic etching conditions in this example. That is, a phosphoric acid concentration of 200 g / L, a processing temperature of 60 ° C., and a current flow of 70 A / dm.²The electrolytic etching was performed at a voltage of 20 V for 5 to 10 minutes. In this reaction, the aluminum alloy cylinder was etched by about 30 μm, so that aluminum was eluted into the acid solution.
[0037]
(Table 1: electrolytic etching conditions)
Phosphoric acid 200g / L
Temperature 60 ℃
Electricity 70A / dm²
Voltage 20V
Processing time 5-10 minutes
Etching amount 30μm
[0038]
Here, in order to recover an acid from a used acid solution (used acid 71) generated by the electrolytic etching treatment, diffusion dialysis was performed as follows. That is, as shown in FIG. 8, the spent acid 71 recovered from the electrolytic etching tank 81 through the used acid line 82 was introduced into the diffusion dialysis device 70. The pure water 72 produced by the pure water producing device 83 was introduced into the diffusion dialysis device 70 through a pure water line 84.
The spent acid 71 and the pure water 72 are introduced into the diffusion dialysis device 70 through the diffusion dialysis membrane 85, where the diffusion dialysis occurs as described above, and the free acid in the spent acid 71 is purified water. 72. The recovered acid 73 was sent to a concentration tank 87 through a recovery acid line 86. The concentration tank 87 is provided with a heater 88, and the recovered acid 73 is concentrated by heating the recovered acid 73 by the heater 88, so that the recovered acid 73 can have a desired concentration. The concentrated recovered acid 73 is sent to the electrolytic etching tank 81, where it is reused. In addition, the residual liquid 74 generated by diffusion dialysis of the used acid 71 is sent to the anodizing tank 90 through the recycled acid line 87 and used there.
[0039]
For dialysis, a stack of 100 APS-type dialysis membranes (about 30 cm × 50 cm) manufactured by Asahi Glass was used at a temperature of 50 ° C. and a flow rate of 10 L / H. FIG. 9 shows a material balance in the diffusion dialysis apparatus 70 according to the present embodiment. As the used acid 71 for electrolytic etching, a solution in which aluminum was dissolved at 10 g / L in an aqueous solution of phosphoric acid at 200 g / L was used. When the used acid 71 and the pure water 72 are introduced into the diffusion dialyzer 70, only the phosphoric acid in the used acid 71 passes through the diffusion dialysis membrane and is dialyzed toward the pure water 70 side.
As a result, a phosphoric acid solution containing no aluminum at a concentration of 160 g / L was obtained as the recovered acid 73. The recovery in this case was 80%. Although the concentration of the recovered acid 73 is lower than the concentration used in the electrolytic etching, when used in the electrolytic etching step, the recovered acid 73 has a concentration effect by evaporation of water, and thus could be used without any problem.
[0040]
Furthermore, since the residual liquid 74 (a diluted acid aqueous solution containing 40 g / L of phosphoric acid containing 10 g / L of aluminum) generated in the diffusion dialysis is recycled in the next anodizing treatment, a new anodizing liquid is used. Need to be prepared. Table 2 shows examples of typical conditions of the anodic oxidation treatment. Since the phosphoric acid concentration may be as low as 50 g / L, it can be used by replenishing the above residual solution (phosphoric acid 40 g / L) with a small amount of phosphoric acid. In the anodic oxidation treatment, problems such as powder blowing and burning are unlikely to occur due to a small amount of electricity, and the permissible range of the dissolved aluminum concentration is larger than that of electrolytic etching. Concentration range. The plated aluminum alloy cylinder manufactured in this example was not inferior to conventional products.
[0041]
(Table 2: Anodizing conditions)
Phosphoric acid 50g / L
Temperature 60 ℃
Electricity 10A / dm²
Voltage 40V
Processing time 5-10 minutes
[0042]
【The invention's effect】
As is clear from the above, according to the present invention, an acid solution such as phosphoric acid is recovered from a used waste liquid generated from an electrolytic etching step and reused in the same step, and a liquid remaining after recovering the acid is recovered. Recycling in the anodizing process can significantly reduce the amount of wastewater treatment in the pre-plating surface treatment method for aluminum alloys, and at the same time greatly reduce the cost of purchasing necessary chemicals such as acids and aluminum salts. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a cylinder processing line of a plating method.
FIG. 2 is a schematic view of a cross section of a plating-coated aluminum alloy.
FIG. 3 is a schematic sectional view showing an example of an anodic electrolytic etching apparatus.
FIG. 4 is a schematic sectional view showing an example of an anode electrolytic etching apparatus.
FIG. 5 is a schematic diagram showing an example of a plating processing line.
FIG. 6 is a schematic diagram of a typical diffusion dialysis device.
FIG. 7 is a schematic view of a plating step according to the present invention.
FIG. 8 is a schematic diagram of a recycling system using the diffusion dialysis device according to the present invention.
FIG. 9 is a schematic diagram showing a material balance in the diffusion dialysis device according to the example.
[Explanation of symbols]
14,81 electrolytic etching tank
17,90 Anodizing tank
20 Plating tank
24 Plating line
31 Aluminum alloy
32 Aluminum oxide layer
33 plating layer
34 Silicon
42, 42a liquid tank
43 Power
44 pump
45, 54 liquid outlet
46,48 insulating plate
47,49 Electrode plate
50 cylinder
51 electrodes
56a, b three-way valve
60 Anion exchange membrane
61 Waste acid
62 water
63,73 Recovered acid
64,74 Permeable liquid
70 Diffusion dialyzer
71 Spent acid
72 pure water
82 Used Acid Line
83 Pure water production equipment
84 Pure water line
85 Diffusion dialysis membrane
86 Recovery acid line
87 Concentration tank
88 heater
89 Recycle acid line

Claims (11)

Electrolytically etching the aluminum alloy using an acid solution;
Anodizing the electrolytically etched aluminum alloy using the same acid-containing solution as the electrolytic etching step,
Recovering the acid from the used acid solution generated in the electrolytic etching step,
Reusing the recovered acid in the electrolytic etching step;
Recovering the acid from the used acid solution and using the remaining solution in the anodizing step. The surface treatment method for an aluminum alloy according to claim 1, wherein the step of recovering the acid is performed by diffusion dialysis. 3. The method for surface treating an aluminum alloy according to claim 1, wherein the step of reusing the recovered acid includes a step of concentrating the recovered acid. 4. The aluminum alloy surface treatment according to any one of claims 1 to 3, wherein, after the electrolytic etching step, the surface of the aluminum alloy is anodized by the anodization step to form an oxidized aluminum alloy layer. Method. The method according to any one of claims 1 to 4, wherein the electrolytic etching step and the anodizing step are performed by using an aluminum alloy containing silicon as an anode, using an insoluble electrode as a cathode, and applying a current in an electrolyte containing the acid. The surface treatment method for an aluminum alloy according to the above. As the acid, phosphoric acid, sulfuric acid, hydrochloric acid, sulfamic acid, a surface treatment method of an aluminum alloy according to any one of claims 1 to 5 using one or more selected from oxalic acid. A method for plating an aluminum alloy, comprising the method for surface treating an aluminum alloy according to any one of claims 1 to 6, further comprising a step of plating the surface-treated aluminum alloy. An electrolytic etching treatment tank for electrolytically etching the aluminum alloy using an acid solution,
Using a solution containing the same acid as the electrolytic etching, anodizing tank for anodizing the aluminum alloy subjected to electrolytic etching,
An acid recovery device for recovering an acid from a used acid solution generated from the electrolytic etching bath,
Means for supplying the acid recovered by the acid recovery apparatus to the electrolytic etching tank;
Means for recovering the acid from the used acid solution and supplying the remaining liquid to the anodizing tank. The surface treatment equipment for an aluminum alloy according to claim 8, wherein the acid recovery device is a diffusion dialysis device. The aluminum alloy surface treatment equipment according to claim 8 or 9, further comprising an acid concentrating tank for concentrating the acid recovered by the acid recovery device. An aluminum alloy plating treatment facility, comprising the aluminum alloy surface treatment facility according to claim 8, further comprising a plating tank for plating the surface-treated aluminum alloy.

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