JP2014051722A - Iron plating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iron plating apparatus in which an iron plating layer can be formed on an article to be plated formed from an aluminum alloy at high speed.SOLUTION: An iron plating apparatus (100) includes: a plating treatment part (10) in which an iron plating layer is formed on a surface of an article to be plated formed by an aluminum alloy; a main tank (20) that supplies a plating solution to a plating treatment part (10); a pH adjustment part (30) that adjusts a pH of a plating solution discharged from a plating treatment part (10); and an iron dissolution tank (40) in which iron is dissolved by a plating solution in which a pH is adjusted by a pH adjustment part (30). A plating solution in which iron is dissolved by an iron dissolution tank (40) is supplied to a main tank (20).

Description

  The present invention relates to an iron plating apparatus, and more particularly to an iron plating apparatus that performs an iron plating process on an object to be plated formed from an aluminum alloy.

  In recent years, in order to meet the needs for higher performance and weight reduction of internal combustion engines, the use of aluminum alloys for internal combustion engine components has been progressing. As one of the wear-resistant treatments for aluminum alloy parts, an iron plating process for forming an iron plating film on the surface of the part is known.

  Patent Document 1 discloses an iron plating apparatus for performing an iron plating process on an aluminum alloy part. The iron plating apparatus disclosed in Patent Document 1 includes a plating bath in which an object to be plated is immersed in a plating solution, and an adjustment bath in which the component concentration of the plating solution discharged from the plating bath is adjusted.

The adjustment bath includes a dissolution tank for making up for insufficient components in the plating solution. In this dissolution tank, iron is dissolved in order to replenish Fe ²⁺ ions that are reduced by the iron plating treatment in the plating bath. Specifically, iron powder is put into the plating solution in the dissolution tank, and dissolution is performed by propeller stirring. Thus, the plating solution whose component concentration is adjusted is sent again to the plating bath and used for the plating process.

JP 2000-265295 A

  However, in the iron plating apparatus disclosed in Patent Document 1, it is difficult to form an iron plating film at a high speed. This is because the pH of the plating solution is not controlled in the iron plating apparatus of Patent Document 1, as will be described in detail later.

  This invention is made | formed in view of the said problem, The objective is to provide the iron plating apparatus which can form an iron plating layer to the to-be-plated object formed from the aluminum alloy at high speed.

  An iron plating apparatus according to the present invention includes a plating processing unit that forms an iron plating layer on the surface of an object to be plated formed from an aluminum alloy, a main tank that supplies a plating solution to the plating processing unit, and the plating processing unit. A pH adjusting unit for adjusting the pH of the discharged plating solution; and an iron dissolving tank in which iron is dissolved by the plating solution whose pH is adjusted by the pH adjusting unit, wherein the iron is dissolved in the iron dissolving tank. A plating solution is supplied to the main tank.

  In one embodiment, the pH adjusting unit reduces the pH of the plating solution.

  In one embodiment, the iron plating apparatus according to the present invention further includes a pipe interconnecting the main tank, the plating treatment unit, and the iron dissolution tank, the main tank, the plating treatment unit, the iron dissolution tank, and The plating solution circulates in the pipe.

  In one embodiment, steel wool is dissolved in the iron dissolution tank.

  In one embodiment, the iron plating apparatus according to the present invention further includes an intermediate tank provided between the iron dissolution tank and the main tank.

  In one embodiment, the intermediate tank is provided with a first tank supplied with a plating solution from the iron dissolution tank and a second tank provided so that a supernatant portion of the plating solution supplied to the first tank flows in. And have.

  In one embodiment, the pH adjusting unit adjusts the pH of the plating solution discharged from the plating unit based on the pH value of the plating solution in the second tank.

  In a certain embodiment, pH value of the plating solution supplied to the said plating process part is 1.25 or more and 1.40 or less.

  In one embodiment, the iron plating layer is an iron-phosphorus alloy film.

  ADVANTAGE OF THE INVENTION According to this invention, the iron plating apparatus which can form an iron plating layer at high speed to the to-be-plated object formed from the aluminum alloy is provided.

It is a figure showing typically iron plating apparatus 100 in an embodiment of the present invention. It is a figure showing typically iron plating apparatus 100A in an embodiment of the present invention. It is a figure showing typically iron plating apparatus 100B in an embodiment of the present invention. It is the cross-sectional photograph of the iron plating layer 71 to which the small piece 72 of steel wool adhered. In the iron plating apparatus 100 shown in FIG. 1, the pH value detected by the pH sensor 62 (the pH value of the plating solution in the main tank 20) and after flowing out of the iron dissolution tank 40 and before flowing into the main tank 20. It is a graph which shows transition of pH value of a plating solution. 3 is a graph showing the transition of the pH value detected by the pH sensor 62 (the pH value of the plating solution in the second tank 52) and the transition of the pH value of the plating solution in the main tank 20 in the iron plating apparatus 100B shown in FIG. is there. It is a cross-sectional photograph of the iron-phosphorus alloy film 71 having fine cracks that do not reach the object to be plated 70. It is a graph which shows the relationship between the melt | dissolution amount (g) of steel wool and iron powder, and melt | dissolution time (minutes) about Example 2 and 3. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, an iron plating apparatus for forming an iron-phosphorus (Fe-P) alloy film as an iron plating layer on the surface of an object to be plated will be exemplified, but the present invention is not limited to this.

  In FIG. 1, the iron plating apparatus 100 in this embodiment is shown. As shown in FIG. 1, the iron plating apparatus 100 includes a plating treatment unit 10, a main tank 20, a pH adjustment unit 30, and an iron dissolution tank 40. Although not shown in FIG. 1, the main tank 20, the plating treatment unit 10, and the iron dissolution tank 40 are connected to each other by a pipe, and the main tank 20, the plating treatment unit 10, the iron dissolution tank 40, and the pipe interior The plating solution circulates.

The plating processing unit 10 forms an iron plating layer on the surface of the object to be plated. Specifically, the plating solution is supplied so as to come into contact with the surface of the object to be plated disposed inside the plating processing unit 10, and in this state, electroplating is performed using the object to be plated as a cathode, thereby performing iron plating. A layer is formed. Here, an iron-phosphorus alloy film is formed as the iron plating layer, but the iron plating layer is not limited to the iron-phosphorus alloy film. For example, an Fe—N alloy film, an Fe—TiO ₂ —P composite film, or an Fe—SiC—P composite film may be formed as the iron plating layer. The iron-phosphorus alloy film is excellent in that it has a high effect of preventing wear and seizure on the sliding surface because the lubricating oil is easily retained. The object to be plated is formed from an aluminum alloy. As the aluminum alloy, known aluminum alloys having various compositions can be used. For example, an Al—Si hypereutectic alloy can be preferably used. The object to be plated is, for example, a cylinder block or a piston for an internal combustion engine. When the object to be plated is a cylinder block, the iron plating layer is formed on the inner peripheral surface of the cylinder bore.

  The main tank 20 supplies a plating solution to the plating processing unit 10. A pump 61 is provided in a pipe connecting the main tank 20 and the plating processing unit 10. Further, in the configuration illustrated in FIG. 1, a pH sensor 62 that detects the pH value of the plating solution in the main tank 20 is provided. A part of the plating solution discharged from the plating processing unit 10 after the plating process is returned to the main tank 20, and the rest flows into the iron dissolution tank 40.

  The pH adjusting unit 30 adjusts the pH (hydrogen ion index) of the plating solution discharged from the plating processing unit 10 (plating solution flowing into the iron dissolution tank 40). Typically, the pH adjusting unit 30 reduces the pH of the plating solution. The pH adjusting unit 30 in the present embodiment includes a pump 31 and a pH adjusting solution storage tank 32 in which hydrochloric acid as a pH adjusting solution is stored, and adjusts the pH based on the pH value detected by the pH sensor 62. By adding hydrochloric acid in the liquid storage tank 32 to the plating solution using the pump 31, the pH of the plating solution is adjusted. In the configuration illustrated in FIG. 1, a check valve 63 for preventing the plating solution from flowing into the pH adjusting unit 30 from a pipe connecting the plating processing unit 10 and the iron dissolution tank 40 is provided. ing.

  In the iron dissolution tank 40, iron is dissolved by the plating solution whose pH is adjusted by the pH adjusting unit 30. Then, a plating solution in which iron is dissolved in the iron dissolution tank 40 is supplied to the main tank 20. In the configuration illustrated in FIG. 1, impurities are removed from the plating solution by the cartridge filter 64 provided between the iron dissolution tank 40 and the main tank 20.

  FIG. 1 shows a valve 65 provided on a pipe connecting the plating processing unit 10 and the iron dissolution tank 40 and a valve 66 provided on a pipe connecting the iron dissolution tank 40 and the main tank 20. Although shown, the number and arrangement of the valves are not limited to those illustrated in FIG.

  As described above, the iron plating apparatus 100 according to the present embodiment includes the pH adjusting unit 30 that adjusts the pH of the plating solution discharged from the plating processing unit 10. Iron is dissolved in the plating solution whose pH is adjusted. This makes it possible to form an iron plating layer at high speed. Hereinafter, this reason will be described in more detail.

When forming an iron-phosphorus alloy film as an iron plating layer at high speed and high current density, an insoluble anode is used. The insoluble anode is, for example, a base made of titanium (Ti) coated with platinum (Pt) or iridium oxide (IrO ₂ ). When an insoluble anode is used, Fe ³⁺ ions are generated by the anodic oxidation reaction of Fe ²⁺ ions represented by the following formula (1) and the water is electrolyzed by the following formula (2). The reaction generates H ⁺ ions.
Fe ²⁺ → Fe ³⁺ + e ⁻ (1)
2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (2)

An increase in Fe ³⁺ ions and a decrease in pH (due to the formation of H ⁺ ions) in the plating solution are caused by a decrease in the surface roughness of the plating film (granular deposition) and the adhesion between the plating film and the object to be plated. It causes deterioration of the quality of the plating film (iron plating layer) such as deterioration. In addition, the cathode current efficiency is lowered, and the plating speed is lowered accordingly.

Therefore, in order to form a high-quality plating film at high speed, it is preferable to increase Fe ²⁺ ions and decrease Fe ³⁺ ions in the plating solution supplied to the plating processing unit 10. In the iron plating apparatus 100 of the present embodiment, the plating solution after the plating treatment is caused to flow into the iron dissolution bath 40 to dissolve iron and supplement Fe ²⁺ ions, and to convert Fe ³⁺ ions to Fe ²⁺ ions. To reduce.

The dissolution reaction of iron in the iron dissolution tank 40 is represented by the following formulas (3) and (4).
Fe + 2H ⁺ → Fe ²⁺ + H ₂ (3)
Fe + 2Fe ³⁺ → 3Fe ²⁺ (4)

By the reaction represented by the formula (3), H ⁺ ions are reduced and Fe ²⁺ ions are generated (pH increases with this reaction). Further, Fe ³⁺ ions are reduced to Fe ²⁺ ions by the reaction represented by the formula (4).

In the iron plating apparatus 100 of this embodiment, the pH of the plating solution discharged from the plating processing unit 10 can be adjusted by the pH adjusting unit 30. Therefore, the pH of the plating solution flowing into the iron dissolution tank 40 can be controlled to a value suitable for iron dissolution. Typically, by further reducing the pH of the plating solution after the plating treatment, the pH value becomes suitable for dissolving iron. Therefore, the amount of iron dissolved per unit time can be increased, and more Fe ³⁺ ions can be reduced to Fe ²⁺ ions. Therefore, according to the iron plating apparatus 100 of this embodiment, an iron plating layer can be formed on a workpiece to be plated at a high speed.

  On the other hand, in the iron plating apparatus disclosed in Patent Document 1, although the component concentration of the plating solution is adjusted, the pH of the plating solution is not controlled. difficult.

  The specific configuration of the pH adjusting unit 30 is not limited to that illustrated in FIG. Further, the pH adjusting liquid is not limited to hydrochloric acid, and for example, sulfuric acid or a mixed liquid of hydrochloric acid and sulfuric acid may be used. In order to form a good plating film (iron plating layer), the pH adjusting solution is preferably hydrochloric acid when the plating solution is a chloride bath. Similarly, when the plating solution is a sulfuric acid bath, the pH adjusting solution is preferably sulfuric acid.

  FIG. 1 shows an example in which the pH value of the plating solution in the main tank 20 is detected by the pH sensor 62. However, as in the iron plating apparatus 100A shown in FIG. The pH value of the plating solution before flowing into the main tank 20 after flowing out of the tank 40 may be detected. In this case, in the pH adjusting unit 30, the pH of the plating solution before flowing into the main tank 20 (the detected pH value) is the pH of the plating solution in the main tank 20 (that is, the plating supplied to the plating processing unit 10). The pH is adjusted to be slightly higher than the pH of the solution (specifically, the supply amount of hydrochloric acid is adjusted). Since the pH of the plating solution discharged from the plating processing unit 10 and returned to the main tank 20 is lower than the pH of the plating solution supplied from the main tank 20 to the plating processing unit 10, the main tank 20 directly from the plating processing unit 10. By mixing the plating solution returned to 1 and the plating solution flowing in from the iron dissolution tank 40 in the main tank 20, the pH of the plating liquid in the main tank 20 is adjusted within a certain range.

  From the viewpoint of reducing the size of the iron dissolution tank 40, it is preferable to dissolve steel wool in the iron dissolution tank 40. When using iron powder (that is, dissolving iron powder in the iron dissolution tank 40), in order to prevent the aggregation of iron powder and increase the reduction efficiency, it is preferable to provide a stirrer in the iron dissolution tank 40, In this case, the iron dissolution tank 40 becomes large. On the other hand, when steel wool is used, a sufficiently large contact area with the solution (plating solution) can be ensured without providing a stirrer, so that the iron dissolution tank 40 can be downsized.

  Moreover, it is preferable that the iron dissolution tank 40 has a double structure including an inner tank 41 and an outer tank 42 (for example, each is cylindrical) as shown in FIG. The double-structure iron dissolution bath 40 has a plating solution inflow portion at the lower portion of the outer bath 42 and a plating solution outflow portion at the lower portion of the inner bath 41. Further, the double-structure iron dissolution tank 40 has a removable cartridge in the inner tank 41, and this cartridge is filled with steel wool. The plating solution flows into the iron dissolution tank 40 from the inflow part at the lower part of the outer tank 42, passes through the inner side of the outer tank 42 (and the outer side of the inner tank 41), and flows into the upper end of the cartridge from the upper part of the inner tank 41. The plating solution dissolves the steel wool while passing through the steel wool while flowing from the top to the bottom of the cartridge, and flows out of the iron dissolution tank 40 from the outflow portion at the bottom of the inner tank 41. At that time, the inside of the inner tank 41 is filled with the plating solution so that the entire cartridge is immersed in the plating solution. By adopting such a structure, dissolution of steel wool can be further promoted. Further, by providing an opening in the upper part of the inner tub 41 where the cartridge can be attached and detached, the cartridge containing the steel wool can be easily replaced. Therefore, working efficiency is improved and continuous plating can be easily performed.

  Furthermore, it is also preferable to provide the intermediate tank 50 between the iron dissolution tank 40 and the main tank 20 as in the iron plating apparatus 100B shown in FIG. 3 for the following reason.

  The plating solution flowing from the iron dissolution tank 40 into the main tank 20 may contain steel wool (small pieces of steel wool) that cannot be completely dissolved and becomes fine. This is because small pieces of steel wool that could not be completely dissolved in the iron dissolution tank 40 may flow into the main tank 20 without being completely removed by the cartridge filter 64. If a plating solution containing such a piece of steel wool is supplied from the main tank 20 to the plating processing unit 10, it may adhere to the iron plating layer and cause a defect. FIG. 4 shows a cross-sectional photograph of the iron plating layer to which small pieces of steel wool are attached. In the example shown in FIG. 4, it can be seen that small pieces 72 of steel wool having a size of about 300 μm are attached to the iron plating layer 71 formed on the surface of the workpiece 70.

  When the intermediate tank 50 is provided between the iron dissolution tank 40 and the main tank 20, the steel wool pieces are dissolved or precipitated in the intermediate tank 50, and therefore do not flow into the main tank 20. Therefore, the occurrence of defects as described above is prevented.

  In the configuration shown in FIG. 3, the intermediate tank 50 is provided so that the first tank 51 supplied with the plating solution from the iron dissolution tank 40 and the supernatant portion of the plating solution supplied to the first tank 51 flow in. And a second tank 52. The plating solution is supplied from the second tank 52 to the main tank 20. When the intermediate tank 50 has such a two-tank structure, inflow of small pieces of steel wool into the main tank 20 is more reliably prevented. Furthermore, when the intermediate tank 50 is opened to the atmosphere (that is, when the intermediate tank 50 opened to the atmosphere is provided), hydrogen gas generated when iron is dissolved can be removed from the plating solution.

  In the configuration shown in FIG. 3, the pH sensor 62 detects the pH value of the plating solution in the second tank 52. When the pH adjusting unit 30 adjusts the pH of the plating solution discharged from the plating processing unit 10 based on the pH value of the plating solution in the second tank 52, the variation of the pH of the plating solution in the main tank 20 is reduced. Therefore, the quality of the iron plating layer (here, the iron-phosphorus alloy film) is further stabilized.

  5 shows the transition of the pH value detected by the pH sensor 62 (that is, the pH value of the plating solution in the main tank 20) in the iron plating apparatus 100 shown in FIG. The transition of the pH value of the plating solution before flowing into the plate is shown. 6 shows the transition of the pH value detected by the pH sensor 62 (that is, the pH value of the plating solution in the second tank 52) and the pH of the plating solution in the main tank 20 in the iron plating apparatus 100B shown in FIG. Shows the transition of values. 5 and 6, when the detected pH value becomes 1.4, supply of hydrochloric acid by the pump 31 is started, and when the detected pH value becomes 1.36, supply of hydrochloric acid by the pump 31 is started. Stop.

  As in the iron plating apparatus 100 shown in FIG. 1, when the pH value of the plating solution in the main tank 20 is detected by the pH sensor 62 and the pH adjusting unit 30 adjusts the pH based on the detected pH value, As shown in FIG. 5, the pH value of the plating solution in the main tank 20 varies in the range of 1.27 to 1.43.

  On the other hand, like the iron plating apparatus 100B shown in FIG. 3, the pH sensor 62 detects the pH value of the plating solution in the second tank 52 of the intermediate tank 50, and adjusts the pH based on the detected pH value. When the unit 30 adjusts the pH, as shown in FIG. 6, the pH value of the plating solution in the main tank 20 varies gently after the start of plating and hardly falls below 1.36.

  As described above, when the pH adjusting unit 30 adjusts the pH of the plating solution discharged from the plating processing unit 10 based on the pH value of the plating solution in the second tank 52, the pH of the plating solution in the main tank 20 is adjusted. Variation can be reduced.

Here, a preferable composition of the plating solution will be described from the viewpoint of the quality of the iron-phosphorus alloy film. As a plating solution for electroplating of an iron-phosphorus alloy (also called a plating bath when placed in a plating tank), a plating solution (sulfuric acid) containing ferrous sulfate as a main source as a source of Fe ²⁺ ions. Bath), a plating solution mainly composed of ferrous sulfate and ferrous chloride, and a plating solution mainly composed of ferrous chloride (a chloride bath).

  However, when a thick iron-phosphorus alloy film is formed at a high current density using the former two plating solutions, that is, a plating solution containing ferrous sulfate, the iron-phosphorus alloy film reaches the object to be plated. Macro cracks may occur.

On the other hand, when a plating solution containing ferrous chloride as a main component is used and the concentration of hypophosphorous acid (H ₃ PO ₂ ) is relatively low, high current density and thick iron (for example, 100 μm to 150 μm) Even if the phosphorus alloy film is formed, the occurrence of macro cracks can be suppressed. FIG. 7 shows a cross-sectional photograph of the iron-phosphorus alloy film in which the occurrence of macro cracks is suppressed. From FIG. 7, it can be seen that macro cracks that reach the object 70 are not generated in the iron-phosphorus alloy film 71.

  Moreover, when the hypophosphorous acid content of the plating solution is 0.01 g / L or more and 1.0 g / L or less, an iron-phosphorus alloy film having a smooth surface and excellent adhesion can be formed. Therefore, when such an iron-phosphorus alloy film is formed on the inner peripheral surface of the cylinder bore of the aluminum alloy cylinder block, the polishing step and the honing step can be omitted. Furthermore, as shown in FIG. 7, since the surface of the iron-phosphorus alloy film has fine cracks (not macro cracks reaching the object to be plated), lubricating oil is held in the cracks, pistons, etc. The slidability with the other material is improved. From the viewpoint of obtaining these effects more reliably, the hypophosphorous acid content of the plating solution is more preferably 0.1 g / L or more and 0.5 g / L or less.

The content of ferrous chloride as a supply source of Fe ²⁺ ions in the plating solution is preferably 350 g / L or more and 450 g / L or less. Further, from the viewpoint of improving the plating speed, the pH value of the plating solution supplied to the plating unit 10 (that is, the pH value of the plating solution in the main tank 20) is 1.0 or more and 1.5 or less. Is preferable, and it is more preferable that it is 1.25 or more and 1.40 or less. Furthermore, when performing a plating process with such a plating solution at a high current density, the temperature of the plating solution is preferably 50 ° C. or higher and 70 ° C. or lower, and more preferably 60 ° C. or higher and 70 ° C. or lower. The cathode current density is preferably at 100A / dm ² or more 200A / dm ² or less, and more preferably 100A / dm ² or more 150A / dm ² or less.

  As already explained, in the iron plating apparatuses 100, 100 </ b> A and 100 </ b> B of this embodiment, the pH is adjusted with respect to the plating solution before flowing into the iron dissolution tank 40. Here, when hydrochloric acid is added to the plating solution before flowing into the iron dissolution tank 40 (Example 1), and against the plating solution before flowing into the main tank 20 after flowing out from the iron dissolution tank 40 The results of comparing the amount of steel wool dissolved in the case of adding hydrochloric acid (Comparative Example 1) will be described. Conditions for measuring the dissolution amount (the composition of the plating solution, the temperature of the plating solution, the pH value of the plating solution in the main tank 20, the capacity of the iron dissolving tank 40, the inflow rate of the plating solution into the iron dissolving tank 40, the plating solution The total amount) is as shown in Table 1 for both Example 1 and Comparative Example 1. Further, with respect to each of Example 1 and Comparative Example 1, the pH value fluctuation and cycle of the plating solution before flowing into the main tank 20 and the period of supply of hydrochloric acid are as shown in Table 2.

  When the dissolution amount of steel wool was measured under the conditions shown in Tables 1 and 2, the dissolution amount of steel wool in Comparative Example 1 was 132 g / Hr, whereas in Example 1, the dissolution amount of steel wool was It was 198 g / Hr. Thus, it was confirmed that the amount of iron dissolved per unit time can be greatly increased by adjusting the pH of the plating solution before flowing into the iron dissolution tank 40.

  Moreover, as already demonstrated, in the iron dissolution tank 40, it is preferable to melt steel wool. Here, the result of comparing the amount of dissolution between the case where the steel wool is dissolved in the iron dissolution tank 40 (Example 2) and the case where the iron powder is dissolved (Example 3) will be described. Conditions for measuring dissolution amount (plating solution composition, plating solution temperature, pH value of plating solution in main tank 20, capacity of iron dissolving bath 40, total amount of plating solution, inflow of plating solution into iron dissolving bath 40 The speed and dissolution time are as shown in Table 3 for both Examples 2 and 3. The fiber center diameter of the steel wool used in Example 2 and the particle size distribution of the iron powder used in Example 3 are as shown in Table 4.

  When the amount of steel wool and iron powder dissolved was measured under the conditions shown in Table 3 and Table 4, the amount of steel wool dissolved in Example 2 and the amount of iron powder dissolved in Example 3 were as shown in Table 5 and FIG. It was as shown in.

  As can be seen from Table 5 and FIG. 8, the amount of dissolution was significantly higher in Example 2 using steel wool than in Example 3 using iron powder. This is because when iron powder is dissolved in the iron dissolution tank 40, the iron powder is fixed and aggregated at the bottom of the iron dissolution tank 40, and the amount of iron powder that is floating may be reduced. This is thought to be due to a decrease. Aggregation of iron powder can be prevented by providing a stirrer in the iron dissolution tank 40, but in that case, the iron dissolution tank 40 is enlarged.

  ADVANTAGE OF THE INVENTION According to this invention, the iron plating apparatus which can form an iron plating layer at high speed to the to-be-plated object formed from the aluminum alloy is provided. The iron plating apparatus by this invention is used suitably for the iron plating process with respect to various aluminum alloy members (for example, cylinder block for internal combustion engines).

DESCRIPTION OF SYMBOLS 10 Plating part 20 Main tank 30 pH adjustment part 31 Pump 32 pH adjustment liquid storage tank 40 Iron dissolution tank 41 Inner tank 42 Outer tank 50 Intermediate tank 51 First tank 52 Second tank 61 Pump 62 pH sensor 63 Check valve 64 Cartridge filter 65, 66 Valve 70 Plated object 71 Iron plating layer (iron-phosphorus alloy film)
72 Small pieces of steel wool 100, 100A, 100B Iron plating equipment

Claims (9)

A plating treatment section for forming an iron plating layer on the surface of an object to be plated formed of an aluminum alloy;
A main tank for supplying a plating solution to the plating section;
A pH adjusting unit for adjusting the pH of the plating solution discharged from the plating processing unit;
An iron dissolving tank in which iron is dissolved in a plating solution whose pH is adjusted by the pH adjusting unit,
An iron plating apparatus in which a plating solution in which iron is dissolved in the iron dissolution tank is supplied to the main tank.   The iron plating apparatus according to claim 1, wherein the pH adjusting unit reduces the pH of the plating solution. Further comprising a pipe interconnecting the main tank, the plating treatment section and the iron dissolution tank,
The iron plating apparatus according to claim 1 or 2, wherein the plating solution circulates in the main tank, the plating processing unit, the iron dissolution tank, and the pipe.   The iron plating apparatus according to any one of claims 1 to 3, wherein steel wool is dissolved in the iron dissolution tank.   The iron plating apparatus according to any one of claims 1 to 4, further comprising an intermediate tank provided between the iron dissolution tank and the main tank.   The said intermediate tank has a 1st tank supplied with the plating solution from the said iron dissolution tank, and a 2nd tank provided so that the supernatant part of the plating solution supplied to the said 1st tank may flow in. 5. The iron plating apparatus according to 5.   The iron plating apparatus according to claim 6, wherein the pH adjusting unit adjusts the pH of the plating solution discharged from the plating unit based on the pH value of the plating solution in the second tank.   The iron plating apparatus according to any one of claims 1 to 7, wherein a pH value of a plating solution supplied to the plating processing unit is 1.25 or more and 1.40 or less.   The iron plating apparatus according to claim 1, wherein the iron plating layer is an iron-phosphorus alloy film.

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