JPS59145799A - Electrolytic coloring method of anodized film of aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To enable coloring of an anodized film of Al from pale brown to dark brown colors as desired in the stage of coloring electrolytically said film using an Ni-salt bath by setting the voltage for electrolysis in specific range and controlling an electrolyzing time. CONSTITUTION:Coloring is performed for the electrolyzing time controlled by using the voltage between the primary peak voltage I v and secondary peak voltage IIv of a correlation curve of the three factors; current, voltage and electrolyzing time of an electrolytic bath in the stage of coloring the anodized film of Al or Al alloy by using an Ni-salt bath. More specifically, the 1st peak current I i and the 2nd peak current IIi appear in the curve indicating the relative reltion among the current, voltage and electrolyzing time in the stage of electrolysis, and the voltages corresponding to the same are the primary peak voltage I v, secondary peak voltage IIv which are made I v <= electrolyzing voltage <= IIv. If the electrolytic coloring is started at I v and is stopped at IIv, the darkening of the color arises in this region with time and if the voltage is set in this range, the prescribed coloring is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrolytically coloring pre-anodized aluminum or an aluminum alloy to any color from light brown to dark brown.

Conventionally, as a method for coloring an anodic oxide film of aluminum, a method as disclosed in Japanese Patent Application Laid-open No. 44939/1983 is known. This method darkens the color by alternately switching the polarity of the electrolyte. However, in the actual production process, this method requires changing the current, voltage, and electrolyte as the polarity is switched. Difficult to control time etc.
It is troublesome and difficult to manage on-site production.

As a result of extensive research into this problem, the inventor found that
When coloring a brown color using a nickel salt bath,
A correlation curve of three factors: current-voltage-electrolysis time during electrolysis, at a voltage intermediate between the first peak voltage and the second peak voltage that causes the first and second peak currents. , electrolytic coloring produces a color ranging from light brown to rich brown (
It has been discovered that it is possible to adjust the temperature as desired up to (blank).

The present invention has been made based on this new knowledge, and the gist of this invention is to apply a current to the electrolytic bath when electrolytically coloring an anodic oxide film of aluminum or aluminum alloy using a nickel salt bath.

In the correlation curve of the three factors of voltage and electrolysis time, the electrolysis time is controlled at an intermediate voltage between the first peak voltage 1V and the second peak voltage ■■ to change the color from light brown to dark brown (black).
This is an electrolytic coloring method for an anodic oxide film of aluminum or an aluminum alloy, which is characterized by coloring an anodic oxide film of aluminum or an aluminum alloy at will.

Here, the first peak voltage and the second peak voltage will be explained in detail.

Current and voltage during electrolysis used in the present invention.

The relative relationship between electrolysis times is expressed by a curve as shown in FIG. Peak values represented by ■λ and ■λ appear on the current curve. I4 is the first peak current and 11λ is the second peak current.

The voltage corresponding to I is the first peak voltage Nv), and the voltage corresponding to I (Ilv) is the second peak voltage.

The relationship between this electrolytic voltage and the electrolytic coloring is as follows.

(1) When electrolytic voltage < Iv No coloration occurs in this area.

When f211v≦electrolytic voltage<IIv, electrolytic coloring starts at Iv. Coloring stops at point IIv. In this range, color deepening occurs as time progresses. Therefore, by setting the voltage within this range, it is possible to freely color the color to any desired intensity.

(3) Region where electrolytic voltage≧Ilv In this region, the color does not deepen over time and remains light brown.

The reason why the voltage of the present invention is limited to a range of Iv or more and less than Ilv is because of the reasons described above.

Although the coloring mechanism of the present invention has not yet been completely elucidated, the following is assumed.

That is, since the present invention uses cathode electrolysis, the reduction reaction of nickel ions progresses more actively within the above voltage range, thereby deepening the color tone.

It is thought that N1 begins to precipitate at exactly 1V, and an insulating film with high electrical resistance is formed at Uv.

Next, the present invention will be explained by examples.

Examples Aluminum and aluminum alloys having the compositions shown in Table 1 were used as test pieces. In addition, component elements are weight%
Shown as

A. Pretreatment The above test piece was subjected to the following pretreatment for anodizing treatment.

■ Degrease by immersing in 10% Na011 melt at 50℃ for 30 seconds ■ Clean with tap water and distilled water ■ 10% 1INO! After neutralization by immersion in the solution for 1 minute, water washing B, anodizing treatment bath composition and electrolysis conditions are as follows.

Bath composition Sulfuric acid: 8W/V% Aluminum sulfate: 2W/V% Electrolytic conditions current: 1.5A/dm2 1W voltage: I4~
! 5V electrolysis time: 20 minutes Film thickness: Approximately 10μm Liquid temperature: 20'C Using a bath using nickel sulfate as C9 electrolytic coloring nickel salt.
The second test piece was electrolytically colored.

The bath composition and electrolytic conditions are as follows.

Bath composition: 9% nickel sulfate, 7H20, 3% boric acid aqueous solution pH: '3.65 Electrolytic conditions: Anode: Nisokel cathode: Above material after anodizing treatment Liquid temperature: 20°C Under the above conditions, Iv and Ilv FIG. 2 shows the correlation between current, voltage, and electrolysis time when electrolysis is performed by applying a DC voltage between the two.

The peak current and voltage of each aluminum material were as shown in Table 2.

Table 2 No coloring occurred until then.

Coloring started from a point past Iv, and the color tone began to deepen with time.

In this example, the set voltage was set to a voltage corresponding to the bottom part of the current curve up to the transition to the primary peak current, that is, the part where the current curve changes from r^ to {circle around (2)} in FIG.

A rich brown (black) was obtained with an electrolysis time of 140 seconds.

For comparison, electrolysis was also performed at a voltage of IIv or higher, but no concentration occurred over time. Only a light brown color was obtained.

As described in detail above, the present invention can be easily colored from light brown (bronze) to rich brown (blank) by using the conventional direct/molar electrolyzer as is. Moreover, the color tone can be controlled by simply changing the electric IW time using 4J, and the coloring time to a rich brown (black) is as short as 140 seconds, compared to conventional methods (Asada method and JP-A-Sho method). 50-44939) in about 10 minutes, the coloring process is five times faster, leading to improved productivity, and is highly effective in practical applications. It can be used in a wide range of applications, including various aluminum building materials and collectors for solar water heaters.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between current and voltage used in the present invention in terms of electrolysis time, and FIG. 2 shows actual measured values of current and voltage in an example of the present invention. Patent applicant: Okinawa Prefectural Industrial Research Institute Yoshimitsu Nagao, agent: Masu Tebori (two idiots)

Claims (1)

[Claims] 1. When electrolytically coloring the anodic oxide film of aluminum or aluminum alloy using a nickel salt bath,
The first peak voltage 1v and the second peak voltage 1 of the correlation curve of three factors: current, voltage, and electrolysis time of the electrolytic bath.
A method for electrolytically coloring an anodic oxide film of aluminum or an alumina alloy, characterized in that the electrolysis time is controlled at a voltage in the range of 1v or more and less than Uv.