JPH0525693A - Locally anodizing method - Google Patents

Abstract

PURPOSE:To realize a locally anodizing method capable of eliminating the need for masking work and applying to the parts having a complex shape. CONSTITUTION:Anodizing liquid 3 is circulated to the inside of the parts 1 on which an anodized film is formed. A coolant flow path 6b is provided to the outside of the parts 1 free from formation of the anodized film. While a coolant 11 is circulated through the flow path 6b and the outside of the parts 1 is cooled, electricity is conducted between an electrode 7 inserted into the inside of the parts 1 and this parts 1. Thereby a locally anodizing method is realized which is applied to rigid anodizing treatment and eliminates the need for masking work and is capable of being efficiently utilized even for the parts having a complex shape at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local anodizing method for forming an anodized film on the surface of aluminum and aluminum alloys.

[0002]

2. Description of the Related Art As a conventional method for forming an anodized film on the surface of aluminum and aluminum alloys,
Generally, as shown in FIG. 5, a method of energizing the cathode rod 13 and the anode rod 14 through the lead wire 15 with the component 1 having the masking material 12 immersed in the anodizing solution 3 in the electrolytic cell 2 ( Immersion method) was adopted. Further, as a special case, as shown in FIG. 6, the anodizing liquid 3 pumped up from the liquid storage tank 4 is brought into contact with the surface 5 to be treated of the component 1, that is, the anodizing liquid 3 is fixed to the jig 6 made of hard vinyl chloride. A method (liquid circulation method) of injecting into the space surrounded by the component 1 from the liquid supply pipe 7 which also serves as an electrode and energizing the liquid supply pipe 7 while circulating between the liquid storage tank 4 and It was sometimes taken.

[0003]

In the anodizing treatment, it is often desired to form the anodized film only on a part of the surface of the component.

In this case, in the conventional method, generally, a portion where an anodizing film is not desired to be formed is covered with an insulating masking material prior to the anodizing treatment, and then the anodizing treatment is performed by the dipping method. However, if there are many parts where you do not want to form an anodized film on the part, that part is complicated in shape, or if the part size is large, this method requires time for masking work and is appropriate. There wasn't.

In this case, the above-mentioned liquid circulation method is adopted, but the conventional liquid circulation method is applicable to the sulfuric acid anodizing treatment and the chromic acid anodizing treatment, which have a slow film formation rate among the anodizing treatments. However, the hard anodizing treatment that forms a thick anodized film at a high speed did not form a film well and was not applicable.

An object of the present invention is to solve the above problems of the conventional method and to provide a method capable of locally forming a uniform and smooth hard anodized film having a thickness of 50 μm or more.

[0007]

According to the method for local anodizing of the present invention, the inside of a part on which an anodized film is formed is sealed and an electrode is inserted therein, and the outside of the part which does not form the anodized film is a jig. To form a coolant channel between the jig and the outside of the component, circulate an anodizing liquid inside the component, circulate the coolant in the coolant channel, and energize between the component and the electrode. Is characterized by.

[0008]

In the above, the anodizing liquid is supplied from the outside to the inside of the component forming the anodizing film on its surface, and circulates. On the outside of the part on which the anodized film is not formed, the coolant is supplied to the coolant channel from the outside and circulated so that the coolant contacts and is cooled.

In this state, when electricity is applied between the component and the electrode,
No anodized film is formed on the outside of the part, and a good anodized film is formed on the inside surface of the part.

Regarding the above, when the anodizing treatment by the conventional liquid circulation method is carried out, defective film formation occurs because heat radiation from the back side of the surface to be treated of the component is insufficient. It depends on what was found as a result of the calculation and examination.

By the above, a local anodizing method which can be applied to a hard anodizing treatment, does not require a masking work, and can be efficiently performed at low cost even for a component having a complicated shape is realized.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus to which the method of the first embodiment of the present invention is applied will be described with reference to FIGS. 1 and 2
The apparatus shown in FIG. 2 is for the case where the method of the present embodiment is applied to anodizing treatment of an aluminum cylindrical component, and is provided at the upper and lower ends of the component 1 whose inner surface is anodized and which seals the inside of the component 1. A jig 6 made of vinyl, an outer cylinder jig 6a provided on the side of the component 1 to form a cooling water flow path 6b between the jig 1 and the upper and lower ends thereof and joined to the jig 6 made of vinyl chloride. One end penetrates the vinyl chloride jig 6 at the upper end and is inserted into the component 1 and is made of stainless steel and also serves as an electrode. The liquid feed pipe 7 is connected to the other end of the liquid feed pipe 7 and the component 1. Between the liquid tank 4 for circulating the anodizing liquid 3 by the pump 19, the refrigerator 8 connected to the liquid tank 4 for cooling the anodizing liquid 3, and the pipe 6b connected to the cooling water flow passage 6b. Tank for circulating cooling water by pump 19a , And a refrigerator 8a which is connected to the water storage tank 9 for cooling the cooling water.

In the above, the anodizing liquid 3 pumped up from the liquid storage tank 4 is made of stainless steel which also serves as an electrode, in a space surrounded by the hard vinyl chloride jig 6 and the aluminum part 1 having an inner diameter of 60 mm. It is injected from the liquid pipe 7 and then discharged, and circulates between the liquid pipe 7 and the liquid storage tank 4. In the liquid storage tank 4, the anodizing liquid is cooled by the refrigerator 8 and kept at 5 ° C. On the other hand, from the water tank 9, the cooling water 11 kept at 5 ° C. like the anodizing liquid is pumped up by the refrigerator 8a and formed between the back side 10 of the surface to be treated of the component and the outer cylinder jig 6a. It is injected into the cooling water channel 6b and circulates with the water tank 9 to cool the component 1. In this state, a positive voltage is applied to the component 1 and a negative voltage is applied to the liquid feed pipe 7 that also has the function of an electrode, and the hard anodizing process is performed.

In the method of this embodiment, the poor film formation that occurred when the conventional local anodizing method (liquid circulation method) was applied to the hard anodizing treatment was confirmed by the thermal calculation.
The heat radiated from the surface of the component 1 in contact with the atmosphere, that is, the back side 10 of the surface to be treated of the component 1 is not sufficient, and in some cases, heat is absorbed from the atmosphere in reverse and the electrolytic heat generated by the anodizing treatment is generated in the component 1. It was invented by the fact that the temperature of the component was increased and the temperature of the component was increased and the vicinity of the surface to be treated 5 was overheated.

From the above-mentioned examination results, by cooling the back side 10 of the surface to be processed of the component 1, the electrolytic heat is also radiated from the surface 10, and the component 1 is annealed during the anodizing process.
That is, the temperature of the surface to be treated 5 could be significantly reduced. That is, by cooling the back side 10 of the surface to be processed of the component 1, it is possible to obtain the same component cooling conditions as the immersion method in which the component 1 is completely immersed in the anodizing liquid 3.
It became possible to form a hard anodized film satisfactorily.

The above will be described in more detail with reference to FIG. As shown in FIG. 3A, when the back side 10 of the surface to be processed is not cooled, when the outside air temperature is high, the outside air temperature T _O > the component temperature T _Ma , and the electrolytic heat is removed from the back side 10 of the surface to be processed. On the contrary, heat flows into the component 1 from the outside air. As a result, the component temperature T _Ma increases. On the other hand, FIG. 3 (b)
When the back side 10 of the surface to be processed is cooled as shown in (4), the cooling water temperature T _c <the component temperature T _{Mb is} naturally satisfied, and the electrolytic heat is also removed from the back side 10 of the surface to be processed. As a result, the component temperature T _Mb becomes lower and T _Ma >> T _Mb .

Since the component 1 is made of aluminum and aluminum alloy and has very good heat conduction, the temperature gradient inside the component is extremely small. Further, although the formed anodized film is thin, the thermal conductivity is poor, so that the temperature gradient is large.

The hard anodizing treatment test specifically carried out by the method of this embodiment will be described below. The composition of the anodizing solution is 135 g / liter of sulfuric acid, 15 g / liter of oxalic acid, and the rest is deionized water. The liquid temperature and the flow rate of the anodizing liquid are 5 ° C. and 80 liter / liter, respectively.
The current density is 2.5 to 20 minutes after the start of electrolysis.
The current was increased to 3.0 A / dm ^{2, and} then constant current electrolysis was performed for 50 minutes. During this period, the cooling water temperature was 5 ° C. and the cooling water flow rate was 0.6 m / s.

The quality of the hard anodized film obtained by this anodizing treatment is black-brown in appearance, uniform and smooth, and the film thickness is 55 to 56 μm as measured by an eddy current type film thickness measuring device. Good results were obtained.

As described above, a local anodizing method which can be applied to hard anodizing treatment, does not require masking work, and can be efficiently performed at low cost even for parts having complicated shapes is realized.

Next, a second embodiment of the present invention will be described. This example is the same as the first example except that the anodizing liquid temperature and the cooling water temperature are set to 11 ° C., and the hard anodizing treatment is performed.

The hard anodized film obtained as described above has a blackish brown appearance, is uniform and smooth, and has a film thickness of 52-52.
The thickness was 53 μm, which was a good film as in the first embodiment.

A third embodiment of the present invention will be described with reference to FIG. The present embodiment shown in FIG. 4 is the same as the first embodiment except that an anodizing liquid is used as the coolant, and the hard anodizing treatment is performed. FIG. 4 shows the whole system, in which the anodizing liquid 3 pumped up from the liquid storage tank 4 is branched and sent to the treated surface 5 of the component and the back side 10 of the treated surface. Anodized liquid 3 as coolant
This makes it possible to perform this treatment even in equipment that does not have a cooling water line. The back side 10 of the surface to be treated is not attacked by the anodizing solution and an unnecessary anodizing film is not formed.

The quality of the hard anodized film obtained by this anodizing treatment was black brown in appearance, uniform and smooth, and the film thickness was 54 to 55 μm, which was as good as that of the first embodiment.

[0025]

Industrial Applicability The local anodizing method of the present invention circulates an anodizing liquid inside a component forming an anodizing film, and provides a coolant channel outside the component not forming an anodizing film, and circulates the coolant in the channel. By cooling the outside of the component and energizing it between the component and the electrode inserted inside the component, it is also applicable to hard anodizing treatment, eliminating the need for masking work, and for components with complex shapes. Realize a local anodizing method that can be implemented efficiently and at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory view of a portion surrounding parts of an apparatus applied to a method of a first embodiment of the present invention.

FIG. 2 is an overall explanatory diagram of an apparatus applied to the method of the first embodiment.

FIG. 3 is an explanatory diagram of an operation according to the method of the first embodiment.

FIG. 4 is an overall explanatory diagram of an apparatus applied to the method of the third embodiment of the present invention.

FIG. 5 is an explanatory view of anodizing treatment by a conventional dipping method.

FIG. 6 is an explanatory diagram of anodizing treatment by a conventional liquid circulation method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Parts 3 Anodizing liquid 4 Storage tank 5 Surface to be treated 6 Vinyl chloride jig 6a Outer cylinder jig 6b Cooling water flow path 7 Liquid supply pipes 8 and 8a Refrigerator 9 Water storage tank 10 Backside of surface to be treated 11 Cooling water 19 , 19a pump

Claims (1)

Claim: What is claimed is: 1. A jig for forming an anodized film is hermetically sealed, an electrode is inserted therein, and the outside of the anodized film-free part is wrapped with a jig to form the jig. A local anodization characterized by forming a coolant channel between the outside of the component, circulating an anodizing liquid inside the component, circulating coolant in the coolant channel, and energizing between the component and the electrode. Method.