JPH0754598B2 - Surface treatment method for aluminum alloy tape recorder cylinders - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cylinder for a tape recorder for DAT, VTR, etc., and more particularly to a rotary head cylinder for supporting a head in a tape recorder adopting a rotary head recording / reproducing system. .

Conventional technology Conventionally, for cylinders for DAT, VTR, etc., aluminum alloy die casting, because it is lightweight and non-magnetic,
Casting and extruded products are often used. In particular, since the outer peripheral surface on which the tape runs is required to have a high degree of wear resistance, a tape made of an Al-Si alloy having excellent wear resistance is generally used.

The problem to be solved by the invention is that such a conventional cylinder is put to practical use in a state where the surface is not treated after mirror surface cutting, and therefore, due to the primary crystal and eutectic Si particles present on the surface, especially under high temperature and high humidity. There was a problem with the corrosion resistance. That is, there is no problem when used in a relatively low temperature and low humidity environment such as indoors, but for example, a DAT mounted on a car or a portable D used outdoors.
When used in a hot and humid environment such as AT or VTR, there was a risk of corrosion on the surface of the cylinder. When corrosion occurs on the surface of the cylinder, there is a risk that even a slight corrosion product will be transferred to the tape and transported to the surface of the head, causing significant clogging of the head.

For such a problem of corrosion, it is first considered to carry out a normal anodic oxidation treatment using an oxalic acid bath, a sulfuric acid bath or the like as a general anticorrosive surface treatment for aluminum materials, but a general alumite treatment In addition, the surface roughness after processing becomes large, and the base material is an Al-Si alloy and it contains a relatively large amount of impurities, so it is not possible to obtain a uniform film, which is required for a cylinder for tape recorders. It is not possible to satisfy the high level surface characteristics.

The present invention has the following technical background.
It is an object of the present invention to provide a surface treatment method capable of improving the humidity resistance of an Al-Si alloy cylinder without impairing the accuracy characteristics of the surface and eliminating the risk of corrosion in a hot and humid environment. .

Means for Solving the Problems As a means for achieving the above-mentioned object, the present invention adsorbs phosphoric acid, chromic acid, silicic acid, or nitrate ions on the surface of a cylinder, and the adsorbate is used to adsorb aluminum on the surface of an aluminum material. It is intended to suppress the growth of the oxide film and improve the moisture and corrosion resistance.

That is, the present invention is a cylinder made of aluminum alloy,
After degreasing and washing treatment, one kind of aqueous solution selected from phosphoric acid, phosphate, chromic acid, chromate, silicic acid, silicate, nitric acid, nitrate, and phosphate ion, chromate ion , Silicate ion or nitrate ion 100 to 2 respectively
A gist is a surface treatment method of a cylinder for an aluminum alloy tape recorder, which is characterized by dipping treatment in an aqueous solution containing 000 ppm.

In the present invention, phosphoric acid, phosphate, chromic acid, chromate, silicic acid, silicate, nitric acid and nitrate, which are components of the treatment bath, are oxidized by the adsorbate by ion adsorption on the surface of the aluminum material. They are mutually equivalent in terms of actions capable of suppressing the growth of the film, and any one of them can be appropriately selected and used.

Further, the concentration of the treatment bath needs to be in the range of 100 to 2000 ppm in terms of content as phosphate ion, chromate ion, silicate ion, or nitrate ion. That is, if it is less than 100 ppm, it is not possible to obtain sufficient amount of ion adsorption on the surface of the aluminum material to improve the moisture resistance. On the other hand, when the concentration exceeds 2000 ppm, the immersion treatment time for producing a uniform ion adsorption film becomes too short,
The processing operation becomes difficult. The most preferable concentration range is about 800 to 1500 ppm.

EFFECT OF THE INVENTION According to the surface treatment method of the present invention, on the surface of the aluminum alloy cylinder whose surface has been degreased and washed after cutting,
Phosphoric acid, chromic acid, silicic acid or nitrate ions are adsorbed, and the ultra-thin film of uniform angstrom order due to these adsorbates has the effect of suppressing the growth of oxide film on the surface of the aluminum material. Corrosion is prevented. Therefore, due to the improved moisture resistance, it can be suitably used without fear of corrosion even as a tape recorder cylinder used in high temperature and high humidity environments such as DAT for automobiles, DAT and VTR for outdoor use. sell. In addition, this improvement in moisture resistance is
It is also possible to realize the secondary effect that the dew condensation prevention circuit attached to the VTR cylinder for the purpose of preventing corrosion is unnecessary. Moreover, according to the treatment of the present invention, since the above-mentioned ion adsorption is performed on the surface of the cylinder, the film thickness of the adsorbed material is uniform and extremely thin on the order of angstrom, which deteriorates the surface accuracy of the cylinder. Never. That is, unlike the case of the usual alumite treatment, the surface roughness is not increased and the formed film is not uneven. Therefore, good tape running characteristics can be maintained.

Examples Example 1 An Al-Si-based aluminum alloy extruded material was cut into a cylinder for DAT, which was immersed in an organic solvent and a weak alkaline non-etching type pretreatment bath for 2 minutes at 50 ° C. Degreasing A washing process was performed.

Next, the degreasing-cleaned cylinder was immersed in a phosphoric acid aqueous solution containing 800 ppm as phosphate ions at 40 ° C. for 30 seconds.

Example 2 Al that has been subjected to cutting processing and degreasing cleaning treatment in the same manner as in Example 1.
-Si-based alloy cylinder is 1500p as chromate ion
A treatment of immersing the chromic acid aqueous solution containing pm at 50 ° C. for 60 seconds was performed.

Example 3 Al subjected to cutting processing and degreasing cleaning treatment in the same manner as in Example 1
-Si-based alloy cylinder, 2000ppm as silicate ion
Was immersed in a sodium silicate aqueous solution containing 30 ° C. for 20 seconds.

Example 4 Al subjected to cutting processing and degreasing cleaning treatment in the same manner as in Example 1.
The -Si alloy cylinder was immersed for 120 seconds in an aqueous nitric acid solution containing 200 ppm of nitrate ions at 20 ° C.

Comparative Example 1 Al which was subjected to cutting processing and degreasing cleaning treatment in the same manner as in Example 1.
The -Si alloy cylinder was used as a comparative test material in its original state.

(Evaluation) In order to examine the humidity resistance and corrosion resistance of the test materials of Examples 1 to 4 and Comparative Example 1, a constant temperature and humidity test of leaving them in an atmosphere of 60 ° C. and a relative humidity of 95% for 48 hours was performed. The surface condition of each cylinder was observed.

As a result, in the test materials according to Examples 1 to 4, no change was observed on the surface, whereas in the test materials according to Comparative Example 1, white change due to partial corrosion on the surface. The existence of some parts was recognized.

Further, all of the test materials of Examples 1 to 4 maintained good smoothness on the surface.

Claims (1)

[Claims] 1. An aluminum alloy cylinder is degreased and washed, and then phosphoric acid, phosphate, chromic acid, chromate,
1 selected from silicic acid, silicate, nitric acid, nitrate
An aqueous solution of seeds, which comprises phosphate ions, chromate ions,
100 to 2000 ppm of silicate or nitrate, respectively
A method for surface treatment of a cylinder for an aluminum alloy tape recorder, which comprises immersing in an aqueous solution containing the aluminum alloy tape recorder.