JPS5983790A - Surface treatment of aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To form an Alumite film exhibiting a translucent effect only by the process of anodic oxidation, by connecting an Al material to an anode in an Alumite-forming liquid electrolyte containing a proper metal ion, and electrolyzing it with DC of current density higher than that under a conventional Alumite- forming condition. CONSTITUTION:After Al or an Al alloy, esp. an Al-Mg or Al-Si alloy material, is subjected to pretreatment such an degreasily washing, etching and smut removal in a conventional manner, it is anodically oxidized with DC. As the base of a liquid electrolyte to be used in said oxidation, an aqueous phosphoric acid solution is optimum. The concentration of said liquid electrolyte is 5-15V/V%, esp. about 10V/V%, and its temp. is 20-30 deg.C. In addition, a metal ion such as Al ion is let exist in said liquid electrolyte, and electrolytical oxidation is performed with current density, e.g. in the range of 2-4A/cm<2>, higher than that under a conventional Alumite-forming condition. Hence, metal particles included in the Alumite film are stable and exhibit excellent fire resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for producing an opaque alumite film on the surface of aluminum or aluminum alloy.

In the following description, aluminum or aluminum alloy will be collectively referred to as aluminum material.

The present invention is a unique method for surface treatment of aluminum materials, with the aim of producing an opaque alumite film using only the anodizing process. By performing this in an electrolytic solution for alumite production, eight gold particles are injected into the alumite film, and the diffused reflection of light by the metal particles is intended to give the alumite film an opaque feel. That is, the method for surface treatment of aluminum materials of the present invention involves connecting an aluminum material to an anode in an alumite production tube containing appropriate metal ions and an anode in a solution, and applying direct current at a current density higher than that under normal alumite production conditions. The method is characterized in that an opaque alumite film is formed on the aluminum material by electrolytic treatment.

Further, the method of the present invention will be explained in detail. An alloy material, mainly an aluminum-magnesium alloy material or an aluminum-magnesium-silicon alloy material, is suitable for the aluminum material to be treated, and pure aluminum has a weak opacity effect.

This aluminum material is subjected to pretreatment such as degreasing, cleaning, etching, and smut removal by conventional methods, and then subjected to anodization treatment using direct current.

As the base of the electrolytic solution used in the anodizing process, an appropriate inorganic acid or organic acid can be used, but an aqueous phosphoric acid solution is most suitable. Note that if a sulfuric acid aqueous solution is used as a base, it will not become opaque, and if a chromic acid aqueous solution is used, there will be problems in waste liquid treatment, and both are inappropriate.

The concentration and temperature of the base electrolyte may be the same as those for normal alumite film formation, but good results can be obtained by setting the conditions to make the film slightly thicker. That is, the concentration is j
~/3-V/V%, preferably about 10V/V%, temperature. 20-30°C, preferably 2.5°C plus 11 years. Note that if the temperature is too high, the film will be too thin and will not be opaque; if the temperature is too low, a high voltage will be required, which is uneconomical.

Gold FA to be dissolved in the base electrolyte (Aluminum ions, nickel ions, iron ions, etc. are adopted as the metal ions. When using a phosphoric acid aqueous solution as the base TLF and M solution, phosphoric acid/l / It is used in the form of miniram, nickel phosphate, and ferrous phosphate, each requiring a concentration of lo-309A.The optimum measurement must be selected depending on the type of aluminum material used.

Furthermore, as other processing conditions, it is preferable to set the current density higher than the normal alumite production conditions. in particular! Good results are obtained when operating in the range of ~1 l-IJdt. If the current density is too low (2 people/M or less), the film thickness will become too thick and there will be no opacity; if the current density is too high (≠A/dl
(more than 90%), it will be eroded and it will no longer be possible to obtain a film that can withstand practical use. Note that better results can be obtained if the energization time is longer than the normal alumite production conditions. That is, the operation is performed so that the film thickness becomes thicker. Preferably, the value is ≠0 to go, but the optimum value may be selected depending on the type of aluminum material used.

Furthermore, since the total refraction particles incorporated into the alumite film are stable, it exhibits excellent light resistance.

Examples of the present invention will be shown below.

Example/ Aluminum alloy Al0! 2. After pretreatment using conventional methods (degreasing, washing with water, etching, etc.), this aluminum alloy was treated with phosphoric acid 10 V/V% and aluminum phosphate 3 J.
In an aqueous solution of 9A, nickel phosphate, 49/1 (liquid temperature 23'C), the anode was oxidized and the cathode was connected to graphite, and anodized for 41Q minutes at 3A/dPv'' DC. As a result, an 11-speed white alumite skin with an opaque layer and a film thickness of 1 μm was attached.

Example No. Aluminum alloy A3032tlC p pretreatment (
After degreasing, washing with water, etching, etc.), the aluminum alloy was phosphorus m-/OV/V%, γ-luminium phosphate 33-Q/(1, nickel phosphate/lyQ/l).
, aqueous solution of ferrous phosphate 329 (liquid temperature, 2 j ”C
), the anode was connected to the anode, graphite was connected to the anode, and anodization was performed for 4/-0 minutes at a direct current of 3Δ/dM.
A colored alumite film was obtained.

Example 3 After pre-treatment (degreasing, washing with water, etching, etc.) by a conventional method on aluminum alloy A O O O Otsu 3, this aluminum alloy was phosphorus f'J:IO''J/V%, aluminum phosphate 3 .3- Q/l, nickel phosphate/, 49/l
.

Ferrous phosphate 3.2 Q/l aqueous solution (liquid temperature: 25°C)
Connect it to the anode inside, connect graphite to the cathode, and apply DC 3/dye' for 0 minutes. was gotten.

Claims (1)

[Claims] / Aluminum or aluminum alloy is connected to an anode in an electrolytic solution for alumite generation containing appropriate metal ions, and stain removal treatment is performed using a direct current with a higher current density than normal alumite generation conditions. Or surface treatment of aluminum or aluminum alloy characterized by producing an opaque alumite film on the aluminum alloy! Method.