JP2010007170A - Acid etching method, acid etching treatment device and method for producing aluminum-based member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which continuously performs acid etching at a high etching rate without exchanging a treatment liquid. <P>SOLUTION: Disclosed is a method for etching the surface of an aluminum-based member obtained by casting and/or forging an aluminum-based material with a surface treatment liquid of pH ≤3 comprising inorganic acid, and includes feeding steps 2, 11 feeding F ions and alkali metal ions into the surface treatment liquid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acid etching method, an acid etching processing apparatus used for the method, and a method for manufacturing an aluminum-based member using the acid etching method.

  Aluminum base materials and aluminum alloy base materials (hereinafter collectively referred to as “aluminum-based base materials”) are brilliant and lightweight in the materials themselves, and therefore can be used in various fields by taking advantage of these characteristics. It is expanding. For example, iron wheels are mainly used for automobiles. However, since automobiles are required to have higher grades and lighter weight, demand for aluminum wheels made of an aluminum alloy base material is increasing.

  When an aluminum base material is cast or cast into an aluminum wheel, or when it is forged, its surface has a release agent used at the time of casting or forging, an aluminum oxide film, dirt, oil, etc. generated at the time of casting or forging (Hereinafter, these may be collectively referred to as “impurities”). These impurities are factors that reduce the adhesion of the coating film to the aluminum wheel. For this reason, before painting an aluminum wheel, it is necessary to remove the impurities by performing a pretreatment for painting.

  In order to remove the impurities, conventionally, processing by physical processing such as shot blasting, barrel polishing, brush polishing, and buffing is performed on an aluminum wheel obtained by casting or forging an aluminum base material. However, it has been difficult to uniformly treat the design surface of an aluminum wheel having a complicated shape only with these physical treatments.

  For this reason, the chemical etching treatment using an alkaline or acidic treatment solution on the surface of the aluminum wheel is performed as an alternative or in combination with treatment by physical means.

  In the chemical etching treatment using the alkaline treatment liquid, the surface of the aluminum wheel is etched unevenly, so that the glittering surface of the aluminum wheel may be fogged, resulting in poor coating appearance.

  On the other hand, the chemical etching treatment using the acidic treatment liquid has an advantage that etching can be performed uniformly and the appearance of coating is not impaired as compared with the chemical etching method using an alkaline treatment liquid.

  However, in the chemical etching process using the acidic treatment liquid, it is necessary to keep the aluminum concentration in the liquid below a certain level in order to keep the quality of the etched aluminum surface above a certain level. However, when the treatment liquid is repeatedly used for a large number of aluminum wheels, the concentration of aluminum in the liquid gradually increases. For this reason, conventionally, the treatment liquid whose aluminum concentration in the liquid has become higher than a certain level is discarded and a new treatment liquid is prepared.

  As a method for suppressing the disposal of the treatment liquid, a method is disclosed in which precipitation is removed as dissolved aluminum aluminum fluoride in the treatment liquid by adding hydrogen fluoride to the etching treatment liquid (see, for example, Patent Document 1). .

In addition, as a method for removing metal ions in the plating solution, a method using a cation exchange resin is also known (see, for example, Non-Patent Document 1).
Japanese Patent Laid-Open No. 7-62565 (published March 7, 1995) Nishikawa Tadaya, "Influence of impurities in chrome plating and countermeasures", Surface Technology, 40, 653 (1989)

  However, the method of Patent Document 1 has a problem that the etching rate is slow.

  Specifically, since the solubility of aluminum fluoride is relatively high at about 5 g / liter, the method described in Patent Document 1 can manage the aluminum concentration in the treatment liquid only at about 5 g / liter or less. For this reason, even if the method described in Patent Document 1 is used, a large amount of aluminum still remains in the processing solution, and thus the etching rate is slow.

  Further, the method described in Non-Patent Document 1 has a high processing cost and it is difficult to maintain aluminum ions at a constant concentration.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a method of continuously performing acid etching at a high etching rate without exchanging the treatment liquid.

In order to solve the above problems, the present inventor has intensively studied a method for continuously performing acid etching of an aluminum-based member at a high etching rate without exchanging the treatment liquid. In the course of the study, (i) even if phosphoric acid, nitric acid, hydrochloric acid, or the like is used as the inorganic acid, it is impossible to perform etching of 1 g / m ² or more on the aluminum surface; (ii) in addition to the inorganic acid, Etching of 1 g / m ² or more on the aluminum surface if hydrofluoric acid, alkali metal salt of hydrofluoric acid, or complex hydrofluoric acid such as silicohydrofluoric acid or borohydrofluoric acid is included in the surface treatment solution However, if the concentration of aluminum ions in the surface treatment liquid becomes 100 ppm or more while repeatedly performing such acid etching, the etching action is remarkably reduced, and etching of 1 g / m ² or more cannot be performed. ,There was found.

  From the above findings, the present inventors have found that the etching rate becomes faster as the pH is lower, and thus, an alkali metal salt of HF that has never been considered in the surface treatment liquid from the viewpoint of production efficiency. In order to complete the present invention, it is found that the aluminum ions dissolved in the surface treatment liquid can be precipitated by supplying the surface treatment liquid to the surface treatment liquid and the concentration of aluminum ions in the treatment liquid can be maintained at less than 100 ppm. It came.

  That is, the acid etching method according to the present invention is a method in which the surface of an aluminum-based member is acid-etched with a surface treatment solution containing an inorganic acid and having a pH of 3 or less in order to solve the above problems. Including a supplying step of supplying the liquid to the surface treatment liquid.

According to the above method, aluminum ions generated in the surface treatment solution by acid etching are precipitated as cryolite (Na ₃ AlF ₆ ), elpasolite (K ₂ NaAlF ₆ ), etc., so that the aluminum ions are removed from the surface treatment solution. can do. Therefore, even when acid etching is performed on a large number of aluminum-based members such as continuous lines with the treatment liquid, the acid etching can be continuously performed at a high etching rate without replacing the surface treatment liquid on the way. There is an effect.

  Therefore, if the present invention is applied as one step of a continuous line, it is possible to continuously perform acid etching on continuously supplied aluminum-based members.

  In the acid etching method according to the present invention, it is preferable that the surface treatment liquid contains phosphoric acid as the inorganic acid at a concentration of 10 g / L or more and 30 g / L or less. According to the method, for example, when shot blasting is performed, a further effect is achieved that shot residue (Fe) on the surface of the aluminum-based member can be efficiently removed.

  In the acid etching method according to the present invention, the surface treatment liquid preferably further contains complex hydrofluoric acid at a concentration of 0.5 g / L or more and 15 g / L or less. According to the method, the complex hydrofluoric acid supplies HF on the surface of the aluminum-based member in contact with the treatment agent so as to compensate for HF consumed by the etching in a timely manner, so that the aluminum-based member in the surface treatment liquid is used. Changes in the HF concentration near the surface can be suppressed. For this reason, the further effect that acid etching can be performed more uniformly is produced.

  In the acid etching method according to the present invention, the complex hydrofluoric acid is preferably silicohydrofluoric acid. According to this method, there is a further effect that acid etching can be performed at a higher etching rate.

  In the acid etching method according to the present invention, the supplying step is preferably performed by supplying an alkali metal salt of HF to the surface treatment liquid. According to this method, since it is not necessary to use highly corrosive hydrogen fluoride, the acid etching process can be performed more safely.

In the acid etching method according to the present invention, the alkali metal salt of HF is preferably a sodium salt of HF and a potassium salt of HF. According to this method, since aluminum ions generated in the surface treatment liquid by acid etching can be precipitated as elpasolite (K ₂ NaAlF ₆ ) having low solubility, the concentration of aluminum ions in the surface treatment liquid is lower. Can be maintained. Therefore, there is a further effect that acid etching can be performed at a higher etching rate.

  In the acid etching method according to the present invention, it is preferable that the method further includes a precipitate removing step of removing the precipitate generated in the supplying step from the surface treatment liquid, and the acid etching is continuously performed on the plurality of aluminum-based members. The above-mentioned “performing acid etching continuously” means that acid etching treatment is repeatedly performed on a plurality of aluminum-based members without changing the surface treatment liquid. According to this method, the precipitated aluminum ions can be prevented from being eluted again into the surface treatment liquid, and the acid etching treatment can be performed with high efficiency.

In the acid etching method according to the present invention, it is preferable that the supplying step is performed so that the HF concentration in the surface treatment liquid is 0.25 g / L or more. According to the method, the concentration of aluminum ions in the surface treatment liquid can be controlled to be less than 100 ppm. For this reason, there exists the further effect that the etching process of 1 g / m < ² > or more can be performed continuously.

The acid etching method according to the present invention further includes an HF concentration measurement step for measuring the HF concentration in the surface treatment liquid, and the HF concentration is 0.25 g / L based on the HF concentration measured by the HF concentration measurement step. It is preferable to perform the supply step so as to achieve the above. According to the method, since the supplying step is performed so that the HF concentration becomes 0.25 g / L or more based on the HF concentration measured in the HF concentration measuring step, the concentration of aluminum ions in the surface treatment liquid is set to 100 ppm. Can be reliably controlled to less than. For this reason, the further effect that the etching process of 1 g / m < ² > or more can be performed stably continuously is produced.

  The regenerator according to the present invention is a regenerant for an acid etching treatment solution used in the acid etching method according to the present invention, in order to solve the above-described problems, and includes HF and an alkali metal-containing compound, or an alkali metal of HF. It is characterized by containing salt.

According to the above configuration, aluminum ions generated in the surface treatment liquid by acid etching can be precipitated as cryolite (Na ₃ AlF ₆ ), elpasolite (K ₂ NaAlF ₆ ), etc. It can be removed from inside. Therefore, even when acid etching is performed on a large number of aluminum-based members such as continuous lines with the treatment liquid, the acid etching can be continuously performed at a high etching rate without replacing the surface treatment liquid on the way. There is an effect.

In the regenerant according to the present invention, an alkali metal salt of HF is preferably used, and as the alkali metal salt of HF, a sodium salt of HF and a potassium salt of HF are preferably used. According to this configuration, it is possible to aluminum ions generated in the surface treating solution by acid etching, solubility precipitated as low elpasolites (K ₂ NaAlF _6), a lower concentration of aluminum ions in the surface treating solution Can be maintained. Therefore, there is a further effect that acid etching can be performed at a higher etching rate.

  In order to solve the above-described problems, the method for producing an aluminum-based member according to the present invention includes an acid etching step for performing the acid etching method according to the present invention, and a chemical conversion treatment for performing a chemical conversion treatment on the aluminum-based member after the acid etching step. And a coating step of coating the aluminum-based member after the chemical conversion treatment step.

  According to the above method, since the method includes the step of performing the acid etching method according to the present invention, the acid etching can be performed at a high etching rate without replacing the surface treatment liquid. Therefore, there is an effect that the aluminum-based member can be manufactured at a lower cost.

  In order to solve the above problems, an acid etching apparatus according to the present invention is an acid etching apparatus for performing the acid etching method according to the present invention, a treatment tank for storing a surface treatment liquid, and the surface treatment liquid. Sampling means for collecting the liquid to be measured from, HF concentration measuring means for measuring the HF concentration of the liquid to be measured, and supplying the surface treatment liquid in the treatment tank based on the HF concentration measured by the HF concentration measuring means Calculating means for calculating supply amounts of F ions and alkali metal ions, and supply means for supplying F ions and alkali metal ions to the surface treatment liquid in the treatment tank based on the supply amounts calculated by the calculation means; It is characterized by providing.

  According to the said structure, since the acid etching method which concerns on this invention mentioned above can be performed, there exists an effect that acid etching can be performed continuously with a high etching rate, without replacing | exchanging surface treatment liquid.

  In the acid etching apparatus according to the present invention, the HF concentration measuring means is preferably a metal silicon electrode meter. According to the said structure, since the HF density | concentration is measured directly or indirectly, there exists the further effect that an acid etching effect | action can be evaluated accurately, without being influenced by pH etc. of an etching process liquid.

  Specifically, a general method for measuring the HF concentration is a method of measuring F ions, and pH is adjusted to measure HF as F ions. However, HF is partially dissociated in an aqueous solution to produce F ions, but the dissociation state changes depending on the pH of the aqueous solution. On the other hand, since the metal silicon electrode method is a method for measuring the HF concentration in the test liquid using the action of HF that dissolves metal silicon, the acid etching action can be accurately evaluated. .

  As described above, the acid etching method according to the present invention includes a supplying step of supplying F ions and alkali metal ions to the surface treatment liquid.

  For this reason, it is possible to continuously perform acid etching at a high etching rate without replacing the surface treatment liquid, and it is possible to continuously remove an oxide film and a release agent having poor properties on the surface of the aluminum-based member. .

  The method for producing an aluminum-based member according to the present invention includes an acid etching step for performing the acid etching method according to the present invention, a chemical conversion treatment step for performing a chemical conversion treatment on the aluminum-based member after the acid etching step, and a chemical conversion treatment step. And a painting step of painting a later aluminum-based member.

  For this reason, an aluminum-type member can be manufactured at lower cost.

  An embodiment of the present invention will be described as follows.

  In this specification, “weight” is treated as a synonym for “mass”, and “weight%” is treated as a synonym for “mass%”. Further, “ppm” means a value calculated in terms of mass unless otherwise specified, for example, 10,000 ppm means 1% by mass. Furthermore, in this specification, “A to B” indicating a range indicates that the range is A or more and B or less.

  Further, various physical properties listed in the present specification mean values measured by the methods described in the examples described later unless otherwise specified.

  The “aluminum-based substrate” in the present specification intends all substrates mainly including aluminum, including at least an aluminum substrate or an aluminum alloy substrate.

(I) Acid Etching Method The acid etching method according to the present embodiment is a method in which the surface of an aluminum-based member is acid-etched with a surface treatment solution containing an inorganic acid and having a pH of 3 or less. (A) Etching step, (b ) HF concentration measurement step, (c) HF and alkali metal supply step, and (d) precipitate removal step. Details will be described below.

(A) Etching process In the said etching process, the surface of the said aluminum-type member is acid-etched with the surface treatment liquid of pH 3 or less containing an inorganic acid.

  Although it does not specifically limit as an aluminum-type member which can apply the acid etching method which concerns on this Embodiment, For example, an aluminum wheel, an outboard motor body, etc. are mentioned.

  Examples of the inorganic acid include phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, and complex hydrofluoric acid. These may be used alone or in combination of two or more. The concentration of the inorganic acid in the surface treatment liquid is not particularly limited, but can be, for example, in the range of 10 g / L to 30 g / L, and more preferably in the range of 10 g / L to 15 g / L. It can be. If the concentration of the inorganic acid in the surface treatment liquid is within the above range, a stable acid etching action can be obtained.

  When the aluminum-based member to which the acid etching method according to the present embodiment is applied is shot blasted, shot residue (Fe) remains on the surface of the aluminum-based member. When Fe ions dissolve and accumulate in the surface treatment liquid (for example, 500 ppm or more), the ability of the surface treatment liquid to dissolve the shot residue (Fe) decreases. As a result, a shot residue, which is a metal nobler than Al, is left on the surface of the aluminum-based member, and the corrosion resistance after painting is reduced.

  For this reason, when the aluminum-based member is subjected to shot blasting, it is preferable that phosphoric acid is contained as the inorganic acid at a concentration of 10 g / L to 15 g / L. This is because phosphoric acid combines with iron ions dissolved in the treatment solution to form insoluble iron phosphate.

  The pH of the surface treatment solution may be 3 or less, more preferably 2.5 or less, and still more preferably 2.0 or less. If pH is in the said range, acid etching can be performed at a high etching rate.

  The surface treatment liquid preferably further contains complex hydrofluoric acid at a concentration of 0.5 g / L or more and 15 g / L or less. If the concentration of complex hydrofluoric acid is within the above range, more stable acid etching can be performed at a high etching rate.

  Examples of the complex hydrofluoric acid include silicohydrofluoric acid, borohydrofluoric acid, and titanium hydrofluoric acid, and silicohydrofluoric acid is more preferable.

  The treatment temperature in the etching step is not particularly limited, and may be in a temperature range usually used in conventional acid etching. Specifically, in general, it is preferably performed within a range of 20 ° C to 70 ° C, more preferably within a range of 35 ° C to 60 ° C. Etching may be performed in a heated state for the purpose of improving workability.

  Furthermore, ultrasonic treatment may be performed when the aluminum-based member is immersed and etched in the etching treatment solution. Thereby, an etching reaction can be promoted. The acceleration of the etching reaction by this ultrasonic treatment is due to the effects of micro vibration, stirring, defoaming, cavitation and the like by ultrasonic waves.

(B) HF concentration measurement step In the HF concentration measurement step, the HF concentration of the surface treatment liquid is measured. Based on the HF concentration measured in the HF concentration measurement step, a supply step described later is performed so that the HF concentration in the surface treatment liquid is within a predetermined range. The HF concentration in the surface treatment liquid can be measured, for example, with a metal silicon electrode meter.

(C) Supplying step In the supplying step, F ions and alkali metal ions are added to the surface so that the HF concentration in the surface treatment liquid falls within a predetermined range based on the HF concentration measured in the HF concentration measuring step. Supply to processing solution. As a matter of course, the surface treatment liquid may contain F ions and alkali metal ions from the beginning.

  As a specific method for supplying F ions and alkali metal ions to the surface treatment liquid, for example, an alkali metal salt of HF or an HF and alkali metal-containing compound (hereinafter referred to as “an alkali metal salt of HF, or HF and There is a method in which “an alkali metal-containing compound” is sometimes abbreviated as “alkali metal salt of HF or the like” as a regenerating agent of the acid etching treatment liquid.

Examples of the alkali metal salt of HF include sodium salts of HF such as NaF and NaHF ₂ and potassium salts of HF such as KF and KHF ₂ . These may be used alone or in combination of two or more. Among these, it is more preferable to use HF sodium salt and HF potassium salt in combination from the viewpoint of forming elpasolite having low solubility.

  When the HF sodium salt and the HF potassium salt are used in combination, the ratio of the HF sodium salt to the HF potassium salt is within a range of 1: 1.5 to 1: 2.5 in molar ratio. preferable.

  Examples of the alkali metal-containing compound include alkali metal hydroxides such as NaOH and KOH, alkali metal halides such as NaCl and KCl, alkali metal phosphates, alkali metal nitrates, alkali metal sulfates, Examples include alkali metal hydrochlorides. These may be used alone or in combination of two or more. Among these, it is preferable to use sodium salt and potassium salt in combination from the viewpoint of forming elpasolite having low solubility.

  Similarly, when sodium salt and potassium salt are used in combination, the ratio of sodium salt and potassium salt is preferably within a range of 1: 1.5 to 1: 2.5 in terms of molar ratio.

  Moreover, when adding HF and an alkali metal containing compound to the said surface treatment liquid, it is preferable that the molar ratio of HF and an alkali metal containing compound exists in the range of 1: 1-2: 1.

  In the supply step, it is preferable to supply an alkali metal salt of HF or the like to the surface treatment liquid so that the HF concentration in the surface treatment liquid is 0.25 g / L or more, and 0.3 g / L or more. It is more preferable to supply as follows.

  If the HF concentration in the surface treatment liquid is 0.25 g / L or more, the concentration of aluminum ions in the surface treatment liquid can be controlled to about 100 ppm or less, and a decrease in etching rate can be suppressed.

  Further, it is preferable to supply an alkali metal salt of HF or the like to the surface treatment liquid so that the HF concentration in the surface treatment liquid is 5.0 g / L or less, and supply such that the HF concentration is 1.0 g / L or less. More preferably, it is more preferable to supply so that it may become 0.5 g / L or less.

  If the HF concentration in the surface treatment liquid is 5.0 g / L or less, since the amount of HF necessary for precipitating aluminum ions does not exist in the treatment liquid, the etching rate should be a predetermined rate or more. Can be suppressed. Moreover, it can suppress that the usage-amount of the regeneration agent for removal of aluminum ion increases, or the generation amount of aluminum containing sludge increases.

  The HF concentration in the present specification means a value measured using a silicon electrode meter (trade name: Surf Proguard 101N, manufactured by Nippon Paint Co., Ltd.) without diluting the acid etching solution.

  In addition to the regenerant, a replenisher containing an inorganic acid can be added to the treatment liquid according to the reduction rate of the acidity of the treatment liquid. The replenisher can be replenished to the treatment liquid discontinuously or continuously according to the treatment of the member to be treated, and the replenishment amount can be adjusted based on the acidity analysis result of the treatment liquid.

(D) Precipitate removal step In the precipitate removal step, the precipitate generated in the supply step is removed from the surface treatment liquid. In addition, although this Embodiment has demonstrated the case where a deposit removal process is included, it does not restrict to this. The precipitate removing step may not be included. However, when the precipitate removing step is included as in the present embodiment, it is possible to suppress the precipitated aluminum ions from being eluted again into the surface treatment liquid, which is particularly effective.

  In the above description, the case where the acid etching method according to the present embodiment includes the HF concentration measurement step has been described. However, the present invention is not limited to this. The HF concentration measurement step may not be included. If at least the acid etching step and the supply step are included, substantially the same effect as in the present embodiment can be obtained. That is, in this case, the above supply process may be performed as appropriate while performing the above supply process every predetermined time or observing the etching rate without performing management based on the HF concentration.

  However, when the HF concentration measurement step is included as in this embodiment, acid etching can be stably performed at a constant etching rate. For this reason, since an acid etching process can be performed continuously and uniformly, the effect is particularly great.

(II) Regenerating agent for acid etching treatment solution The regenerating agent according to the present embodiment is a regenerating agent for the acid etching treatment solution used in the acid etching method according to the above-described embodiment, and contains HF and an alkali metal. A compound, or an alkali metal salt of HF.

  Examples of the alkali metal-containing compound and the alkali metal salt of HF include the compounds exemplified in “(I) Acid etching method”. Note that the regenerant according to the present embodiment may contain both HF, an alkali metal-containing compound, and an alkali metal salt of HF.

  The content of the HF and alkali metal-containing compound or the alkali metal salt of HF in the regenerant according to the present embodiment is not particularly limited, but is preferably in the range of 1 to 20% by mass, More preferably, it is within the range of 20% by mass.

(III) Acid Etching Apparatus FIG. 1 is a schematic diagram showing a schematic configuration of an acid etching apparatus according to the present embodiment.

  The acid etching processing apparatus according to the present embodiment is an acid etching processing apparatus for performing the above-described acid etching method. As shown in FIG. 1, the processing tank 1 for storing the surface treatment liquid and the surface treatment liquid are coated with the acid etching treatment apparatus. It is measured by sampling means (pump 6 and flow rate control section 7) for collecting the measurement liquid, HF concentration measurement section (HF concentration measurement means) 4 for measuring the HF concentration of the liquid to be measured, and HF concentration measurement section 4. Based on the HF concentration, a control unit (calculation means) 5 for calculating the amount of alkali metal salt or the like of HF supplied to the surface treatment liquid in the treatment tank 1, and based on the amount calculated by the control unit 5, HF Supply means (supplementing tank 2, pump 10 and flow rate control unit 11) for supplying the alkali metal salt or the like to the surface treatment liquid in the processing tank 1.

  In the acid etching processing apparatus according to the present embodiment, the acid etching process can be performed by a conventionally known method by immersing the aluminum-based member in the processing tank 1. In the present specification, the description of members similar to those conventionally known, such as a member for immersing an aluminum-based member, is omitted.

  As shown in FIG. 1, the treatment tank 1 in which the surface treatment liquid is stored is provided with a pipe for supplying the surface treatment liquid to the HF concentration measuring unit 4 as a liquid to be measured. In addition, a flow rate control unit 7 is provided and constitutes sampling means. The flow rate control unit 7 includes a flow rate adjustment valve and a flow meter. The flow rate control unit described below is composed of a flow rate adjustment valve and a flow meter.

  The replenishing tank 2 is provided with a pipe for supplying a solution containing an alkali metal salt of HF or the like (hereinafter referred to as a “HF alkali metal salt etc. solution”) to the treatment tank 1. 10 and a flow rate control unit 11 are provided. Thereby, the supply means is configured.

  A pipe for supplying the liquid to be measured is provided from the sampling means to the HF concentration measuring section 4 as the HF concentration measuring means, and a flow rate control section 12 is provided in this pipe. The HF concentration measurement unit 4 is provided with a pipe for returning the measured liquid after measurement to the treatment tank 1 again. Further, a bypass pipe that does not pass through the HF concentration measuring unit 4 is provided between the sampling means and the processing tank 1, and a flow rate adjusting valve 13 is provided in the bypass pipe.

  The measurement data signal of the HF concentration measured by the HF concentration measurement unit 4 is sent to the control unit 5, and based on this measurement data, the replenishment amount of the HF alkali metal salt solution to be supplied to the treatment tank 1 is determined, A signal for controlling the replenishment amount is sent to the pump 10 and the flow rate control unit 11.

  A metal silicon electrode meter is provided in the HF concentration measuring unit 4, and the HF concentration in the liquid to be measured is measured by the metal silicon electrode meter. As such a structure of the HF concentration measuring unit 4, for example, a structure as shown in FIG. 2 can be adopted.

  FIG. 2 is a cross-sectional view showing a schematic configuration of an example of an HF concentration measurement unit in the acid etching apparatus according to the present embodiment.

  As shown in FIG. 2, in the HF concentration measuring unit 4, an anode metal silicon electrode 20 for detecting the HF concentration and a cathode platinum electrode 21 are flown through the resin pipe 23 in the resin pipe 23. It is provided in contact with the measurement liquid. Further, the resin pipe 23 is provided with another platinum electrode 22 which is a counter electrode at the time of electrolytic cleaning of the cathode in a direction perpendicular to the metal silicon electrode 20 and the platinum electrode 27. With such a structure, the HF concentration in the liquid to be measured flowing through the resin pipe 23 can be measured.

  Hereinafter, the operation of the acid etching apparatus shown in FIG. 1 will be described.

  In the apparatus shown in FIG. 1, a certain amount of liquid to be measured is fed from the surface treatment liquid in the treatment tank 1 to the HF concentration measurement unit 4 to measure the HF concentration. This liquid feeding is performed by the pump 6 and the flow rate control unit 7, and the liquid to be measured is fed to the HF concentration measuring unit 4 at a predetermined flow rate.

  After the HF concentration measurement, the liquid to be measured is returned to the processing tank 1. The flow rate at which the liquid to be measured sampled from the surface treatment liquid in the treatment tank 1 is refluxed in this way can be, for example, 5 liters / minute.

  The sampled solution to be measured is sent to the HF concentration measurement unit 4, and since a bypass is provided here, the solution to be measured that passes through the HF concentration measurement unit 4 by the flow rate control unit 12 and the flow rate adjustment valve 13. The amount of can be adjusted. For example, the amount of the liquid to be measured that passes through the HF concentration measurement unit 4 within a range of 2 to 5 liters / minute can be arbitrarily set.

  The sampled liquid to be measured is measured for HF concentration by the HF concentration measuring unit 4. The measurement data of the HF concentration is transmitted to the control unit 5, and the control unit 5 calculates the amount of alkali metal salt of HF supplied to the surface treatment liquid in the treatment tank 1.

  Based on the calculated amount, a control signal is sent to the pump 10 and the flow rate control unit 11. Based on this transmitted signal, a predetermined amount of HF alkali metal salt solution or the like is supplied from the replenishing tank 2 into the processing tank 1 by the pump 10 and the flow rate control unit 11.

The solution such as HF alkali metal salt supplied in the treatment tank 1 reacts with aluminum ions in the surface treatment liquid in the treatment tank 1, and cryolite (Na ₃ AlF ₆ ), elpasolite (K ₂ NaAlF ₆ ), etc. The aluminum ion is removed from the surface treatment solution. Thereby, the concentration of aluminum ions in the surface treatment liquid is controlled within a predetermined range.

  In FIG. 1, the configuration for removing the precipitate from the surface treatment solution is omitted, but the acid etching processing apparatus according to the present embodiment can employ a conventionally known configuration.

  For example, a hopper or the like that can temporarily store a precipitate and remove the precipitate from the treatment layer 1 as necessary may be provided at the bottom of the treatment tank 1. Moreover, you may further provide the filter for collect | recovering surface treatment liquids from the said slurry-like precipitation taken out. Thereby, the usage-amount of a surface treatment liquid can be reduced.

  Although it does not specifically limit as said filter, For example, a pressure dehydration filter, a pressure concentration filter, etc. are mentioned. These may be used alone or in combination.

  FIG. 3 shows an example of a configuration for removing the precipitate from the surface treatment liquid. As shown in FIG. 3, a hopper 36 capable of temporarily storing a precipitate and removing the precipitate from the treatment layer 1 as needed is provided at the bottom of the treatment tank 1. The slurry-like precipitate removed from the treatment tank 1 is transferred to the pressure concentration filter 32 by the pump 31.

  In the pressure concentration filter 32, a part of the surface treatment liquid is recovered from the slurry-like precipitate and transferred to the treatment tank 1. The remaining slurry-like precipitate is temporarily stored in the drain tank 33 and then transferred to the pressure dehydration filter 34 by the pump 31.

  In the pressure dewatering filter 34, the precipitate 35 is removed from the slurry-like precipitate in the form of a cake, and the remaining surface treatment liquid is transferred to the treatment tank 1.

  As described above, if the acid etching apparatus according to the present embodiment is used, the liquid to be measured is continuously sampled from the processing tank 1 and the HF concentration is measured. By adding a solution such as an HF alkali metal salt, the aluminum concentration in the surface treatment liquid can be controlled to a predetermined value or less.

(IV) Method for Producing Aluminum-Based Member The method for producing an aluminum-based member according to the present embodiment includes a step of performing the acid etching method according to the present embodiment described above.

  As each process other than the process of performing the acid etching method according to the present embodiment described above, which can be included in the method for manufacturing an aluminum-based member according to the present embodiment, for example, a process of molding an aluminum-based substrate, Examples include a release agent removing step, a degreasing step, a chemical conversion treatment step, and a coating step by an appropriate means.

  The step of molding the aluminum base material is a step of molding the aluminum base material, and can be performed by a conventionally known method such as casting and / or forging.

  The release agent removal step by physical means is a step of performing a treatment to remove the release agent and aluminum oxide film remaining on the surface of the aluminum-based member after casting and / or forging by physical means. .

  Specific examples of the physical means include shot blasting. Due to the treatment by such physical means, the mold release agent and the poorly oxidized aluminum oxide film adhering to the surface of the aluminum member, the machine oil adhering to the surface of the aluminum member, and the organic impurities such as cutting oil, etc. Can be removed.

  The degreasing step is a step of removing oil adhering to the surface of the aluminum-based member. In the degreasing step, the method of degreasing the surface of the aluminum-based member is not particularly limited, and a conventionally known method used for degreasing the surface of the aluminum base material may be used.

  In the chemical conversion treatment step, a chemical conversion coating for improving adhesion to the coating and corrosion resistance is formed on the surface of the aluminum-based member processed in the step of performing the acid etching method according to the present embodiment. Specifically, a uniform and dense chemical conversion film is formed in close contact with the base of the aluminum-based member.

  The specific chemical conversion treatment in the chemical conversion treatment step is not particularly limited, and a conventionally known chemical conversion treatment applied to the surface of the aluminum-based member may be performed.

  In the said coating process, it coats on the surface of the aluminum-type member processed in the said chemical conversion treatment process. The coating is not particularly limited, and any conventionally known coating can be used. Specific examples include solvent coating, aqueous coating, and powder coating.

  In addition, in the manufacturing method of the aluminum-type member which concerns on this Embodiment, it is preferable to perform the process of performing the acid etching method which concerns on this Embodiment after a degreasing process, and to perform a chemical conversion treatment process after that.

  Moreover, in the manufacturing method of the aluminum-type member which concerns on this Embodiment, it is preferable to perform a water washing process with respect to an aluminum-type member after the said acid etching process. Thereby, the surface treatment liquid can be washed away (diluted) to stop the etching reaction. Moreover, the amount of the surface treatment liquid brought into the subsequent process can be reduced by the water washing treatment.

  The water washing treatment may be performed under conditions that can stop the etching reaction, but is preferably performed a plurality of times from the viewpoint of efficiency. Thereby, an etching reaction can be stopped reliably.

  Furthermore, in the manufacturing method of the aluminum-based member according to the present embodiment, after the step of performing the acid etching method according to the present embodiment (after the chemical conversion treatment step), the coating film and the aluminum-based member The process (post-processing process) which performs the process which improves adhesiveness may be included.

  By performing the post-processing step, it is possible to widen the selection range of the type of coating applied to the aluminum-based member. If it demonstrates more concretely, even if it is a case where the coating which forms a thick film with high internal stress like a powder coating is given, the adhesiveness with the aluminum system member of a coating film can be improved.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to a following example.

[Al alloy dissolution amount]
The amount of dissolved Al alloy was calculated by calculating the weight loss (P) per treatment area before and after chemical etching.

[Shot residue]
The cast surface of the wheel after the chemical conversion treatment is cut out, and the residue of Fe, which is the main component of the shot grain, is detected by fluorescent X-ray analysis using a Rigaku scanning X-ray fluorescence analyzer ZSX Primus (manufactured by Rigaku Corporation). Quantitative analysis of the amount, the following criteria ○: When Fe residual amount is less than 100 mg / m ² Δ: When Fe residual amount is 100 or more and less than 200 mg / m ² ×: Fe residual amount is 200 mg / m ² Evaluation was made when the value was exceeded.

[Release agent removability]
The wheel surface after chemical conversion treatment is rubbed with white gauze, and the degree of adhesion of black impurities to the white gauze is as follows. X: Adherence of black impurities to white gauze was clearly recognized and evaluated.

[Coating resistance]
The surface of the test piece was cut to a length of 10 cm with a cutter knife, and the cast test solution adjusted according to JISZ2371-2000 was sprayed at 50 ± 2 ° C. for 240 hours, and the degree of corrosion around the cut portion was determined according to the following criteria: Occurrence of blistering or rusting of the coating film is less than 1 mm from the cut portion ○: Fluffing or rusting of the coating film is 1 mm to 3 mm from the cut portion
X: Evaluated when the swelling of the coating film or the occurrence of rust exceeded 3 mm from the cut part.

[PH of surface treatment solution]
The pH of the surface treatment solution was measured at 20 ° C. with a pH meter without dilution.

[Example 1]
The molten aluminum alloy (AC4CH) was cast into an automotive wheel mold coated with a commercially available graphite release agent, cooled, and taken out from the mold.

  Next, after heat treatment, shot blasting was performed as a physical treatment using SUS430 material as shot grains.

  Thereafter, degreasing (immersion treatment at 50 ° C. for 3 minutes) with an alkaline degreasing agent (Surf Cleaner 53NF (manufactured by Nippon Paint Co., Ltd.), 2% by weight) was performed. After the degreasing treatment, immersion water washing was performed in two steps. And the pickling (40 degreeC, 3 minute immersion process) by the pickling process liquid (Surf cleaner 355A (Nippon Paint Co., Ltd. product, 3 weight%)) was performed.

  Next, an acid etching treatment was performed using the apparatus shown in FIG. 1 by the treatment method described in Table 1 with the surface treatment liquid of the components listed in Table 1 (see column of initial composition in Table 1). That is, the acid treatment is performed using the surface treatment liquid having the initial composition shown in Table 1, and the HF conversion concentration of the surface treatment liquid is 0.25 to 0.32 g / L. Replenisher B having the composition was appropriately replenished. In addition, the replenisher A was collected in a set amount (10 mL) of the treatment liquid, neutralized titration analysis was performed with 0.1N caustic soda solution as needed, and replenished according to the rate of decrease in acidity.

  After the acid etching treatment, it was subjected to a chemical conversion treatment (pH = 3.5, 40 ° C., 45 seconds immersion treatment) with a non-chromic chemical conversion treatment agent (Alsurf 501N (manufactured by Nippon Paint Co., Ltd.), 1% by weight). After the chemical conversion treatment, immersion water washing was performed in two steps, and then immersion treatment with pure water was performed. Thereafter, it was dried with hot air at 120 ° C. for 10 minutes and then naturally cooled.

  Thereafter, electrostatic powder coating is carried out with an acrylic powder coating (Powdax A400 Clear (manufactured by Nippon Paint Co., Ltd.)), and the coating thickness ( 100 μm) of primer coating was obtained.

  Next, an acrylic solvent-type paint (Superlac 5000AS70 11SV-14 (manufactured by Nippon Paint Co., Ltd.)) was applied to a dry coating film of 20 μm, set for 10 minutes, and then heated at 140 ° C. for 20 minutes. Next, an acrylic solvent paint (Superlac 5000AW-10 (manufactured by Nippon Paint Co., Ltd.)) was applied to a dry film thickness of 40 μm, set for 10 minutes, then heated at 140 ° C. for 20 minutes to form a multilayer coating. A membrane was prepared.

  Table 1 shows the results of various evaluations on the obtained painted aluminum wheel.

[Examples 2 to 12, Comparative Examples 1 to 5]
The aluminum alloy (AC4CH) was processed in the same manner as in Example 1 except that the shot blasting was performed and the chemical etching conditions were changed to the conditions shown in Table 1. Each evaluation result of the obtained coated aluminum wheel is shown in Tables 1 and 2.

  In addition, NaOH in the initial compositions of Examples 10 and 11 and Comparative Example 5 was added so as to be ½ mol with respect to HF.

As is apparent from Tables 1 and 2, when the acid etching method of the present invention was performed, the amount of Al alloy dissolved was almost unchanged between the initial stage and after 1000 m ² treatment, except for Example 12. In Example 12, the initial composition of the treatment liquid does not contain an alkali metal salt of HF, but since HF and NaOH were added to the treatment liquid as the replenisher B, the Al alloy dissolved after 1000 m ² treatment. The amount was excellent.

In Examples (Examples 2, 3 and 9) in which shot blasting was not performed, the paint durability hardly changed between the initial stage and after 1000 m ² treatment. Even if it is an example (Examples 1 and 4-8) which is performing shot blasting, if it is an example (Examples 1 and 5-8) which contains phosphoric acid in a surface treatment liquid, it is shot residue amount and paint corrosion resistance Was almost unchanged between the initial stage and after 1000 m ² treatment.

  Of course, in Comparative Example 3 where the acid etching treatment was not performed, the paint corrosion resistance was poor.

On the other hand, in Comparative Examples 1 and 2, since the initial composition of the surface treatment agent and the replenishing agent do not contain an alkali metal salt of HF, the Al alloy dissolution amount, the shot residue amount, and the paint corrosion resistance are 1000 m compared to the initial value. ² worsened after treatment. Further, in Comparative Example 4 which initially contains an alkali metal salt of HF but does not contain an alkali metal salt of HF, the dissolution amount of Al alloy, the amount of shot residue, and the corrosion resistance of the paint are 1000 m ² compared with the initial treatment. Later it was worse.

  Moreover, it has confirmed from the comparison with Example 2 containing hydrogen silicofluoride and Example 3 which does not contain that the amount of Al alloy melt | dissolution is larger when hydrogen silicofluoride is contained.

As described above, by using the acid etching method of the present invention, the aluminum wheel surface can be continuously etched by 1 g / m ² or more, and the oxide film and the release agent can be continuously removed. . For this reason, when coating is performed on the aluminum hole subjected to the acid etching treatment, the coating adhesion and the coating corrosion resistance can be improved.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The acid etching method of the present invention can continuously perform acid etching at a high etching rate without changing the treatment liquid. For this reason, it can apply suitably for the acid etching process of various aluminum type members.

It is a schematic diagram which shows schematic structure of the acid etching processing apparatus which concerns on this Embodiment. It is sectional drawing which shows schematic structure of an example of the HF density | concentration measurement part in the acid etching processing apparatus which concerns on this Embodiment. It is a schematic diagram which shows an example of the structure which removes the said precipitation from the surface treatment liquid in the acid etching processing apparatus which concerns on this Embodiment.

Explanation of symbols

1 treatment tank 2 replenishment tank (supply means)
4 HF concentration measuring unit (HF concentration measuring means)
5 Control unit (calculation means)
6 Pump (sampling means)
7 Flow controller (sampling means)
10 Pump (supply means)
11 Flow control unit (supply means)

Claims (14)

It is a method of acid etching the surface of an aluminum-based member with a surface treatment solution containing an inorganic acid and having a pH of 3 or less,
An acid etching method comprising a supplying step of supplying F ions and alkali metal ions to the surface treatment liquid.   The acid etching method according to claim 1, wherein the surface treatment liquid contains phosphoric acid as the inorganic acid at a concentration of 10 g / L to 30 g / L.   The acid etching method according to claim 1, wherein the surface treatment liquid further contains complex hydrofluoric acid at a concentration of 0.5 g / L or more and 15 g / L or less.   The acid etching method according to claim 3, wherein the complex hydrofluoric acid is silicohydrofluoric acid.   The acid etching method according to any one of claims 1 to 4, wherein the supplying step is performed by supplying an alkali metal salt of HF to the surface treatment solution.   6. The acid etching method according to claim 5, wherein the alkali metal salt of HF is a sodium salt of HF and a potassium salt of HF. A precipitate removing step of removing the precipitate generated by the supplying step from the surface treatment liquid;
The acid etching method according to claim 1, wherein acid etching is continuously performed on a plurality of aluminum-based members.   The acid etching method according to any one of claims 1 to 7, wherein the supplying step is performed so that an HF concentration in the surface treatment liquid is 0.25 g / L or more. Furthermore, an HF concentration measurement step for measuring the HF concentration in the surface treatment liquid is included,
The acid according to any one of claims 1 to 7, wherein the supplying step is performed so that the HF concentration becomes 0.25 g / L or more based on the HF concentration measured by the HF concentration measuring step. Etching method. A regenerating agent for an acid etching treatment liquid used in the acid etching method according to any one of claims 1 to 9,
A regenerant comprising HF and an alkali metal-containing compound, or an alkali metal salt of HF. An alkali metal salt of HF,
The regenerant according to claim 10, wherein a sodium salt of HF and a potassium salt of HF are used as the alkali metal salt of HF. An acid etching step for performing the acid etching method according to any one of claims 1 to 9,
A chemical conversion treatment step for performing chemical conversion treatment on the aluminum-based member after the acid etching step;
A coating process for coating the aluminum-based member after the chemical conversion treatment process;
The manufacturing method of the aluminum-type member characterized by including. An acid etching treatment apparatus for performing the acid etching method according to any one of claims 1 to 9,
A treatment tank for storing a surface treatment liquid;
Sampling means for collecting the liquid to be measured from the surface treatment liquid;
HF concentration measuring means for measuring the HF concentration of the liquid to be measured;
Calculation means for calculating the supply amount of F ions and alkali metal ions supplied to the surface treatment liquid in the treatment tank based on the HF concentration measured by the HF concentration measurement means;
Supply means for supplying F ions and alkali metal ions to the surface treatment liquid in the treatment tank based on the supply amount calculated by the calculation means;
An acid etching processing apparatus comprising:   14. The acid etching apparatus according to claim 13, wherein the HF concentration measuring means is a metal silicon electrode meter.

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