JPS5848676A - Chemical treatment of aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To form a film with superior corrosion resistance, a superior wetting property to water and superior suitability to undercoating on the surface of Al without causing environmental pollution in the treatment of waste liquor by treating the Al with desalted water or distilled water before treatment with N,N-dialkylethanolamine. CONSTITUTION:Al or an Al alloy (expressed as Al hereunder) is immersed in desalted water or distilled water contg. additives as required, or the water is sprayed on Al. The Al surface is dissolved and oxidized to form an oxide film on the surface. The Al is then immersed in an aqueous soln. contg. N,N-dialkylethanolamine represented by the formula (where R is 1-4C alkyl), or the soln. is sprayed. Thus, the Al surface can be provided with high corrosion resistance, a high wetting property to water and high suitability to undercoating.

Description

Detailed Description of the Invention The present invention relates to a method for chemical conversion treatment of aluminum or aluminum alloy, in which aluminum or aluminum alloy is treated with demineralized water or distilled water to form an oxide film, and then N,N
-A chemical conversion treatment method for aluminum or aluminum alloys that can produce a surface film with excellent corrosion resistance, water-wetting properties, and coating base properties by treating with a dialkylethanolamine solution, and does not cause pollution problems when carried out. The purpose is to provide

BACKGROUND ART Conventionally, as a chemical conversion treatment method for forming an oxide film on the surface of aluminum or an aluminum alloy (hereinafter simply referred to as aluminum), for example, a chromate method or a boehmite method is known.

Among these chemical conversion treatment methods, the chromate method uses chromic acid,
By immersing aluminum in a chromate treatment solution containing fluoride, cyanide, etc., an oxide film is generated on the aluminum surface. is included, so the cost of treating the wastewater is enormous! However, the cost is high. Furthermore, although the chromate-treated film has relatively good corrosion resistance, it has fatal drawbacks such as extremely poor water-wetting properties on its surface. has disadvantages such as not being suitable.

The boehmite method involves bringing aluminum into contact with heated water or steam at a high temperature of 80°C or higher to form a boehmite film on the aluminum surface. Therefore, as an advantage of this boehmite method, an alkali or alkaline earth metal base such as ammonia, monoethanolamine, jetanolamine, triethanolamine, or Na0)T is added to the heated water. A boehmite method has also been proposed in which the corrosion resistance is improved by keeping the steel in place. However, even with this improved coating made using the boehmite method, relatively light corrosion4
(JIS Z2371 salt water spray test approximately 240 hours)
Although it has some effect.

Severe corrosion binary boundaries, such as O, A, 8. S, Examination (JI
S He5sl) has a fatal drawback in that it has only about half the corrosion protection effect of a chromate film.

The present invention eliminates the above-mentioned drawbacks and does not cause pollution problems during wastewater treatment, making it extremely easy to implement industrially and at low cost.Furthermore, the film produced by the treatment has excellent corrosion resistance and water-wet resistance. They discovered that it has good properties as a base coat.

An embodiment of the chemical conversion treatment method for aluminum or aluminum alloy according to the present invention will be described below.

The chemical conversion treatment method of the present invention can be applied to aluminum or, for example, aluminum-manganese alloy, aluminum-magnesium alloy, aluminum-magnesium-manganese alloy, aluminum-magnesium-silicon alloy, aluminum-copper-magnesium alloy, aluminum By immersing aluminum alloys such as mu-silicon alloys in demineralized water or distilled water, or by spraying this water, the surface of aluminum or aluminum alloys is dissolved and oxidized to form an oxide film on the surface. After that, at least one compound selected from N,N-dialkylethanolamine represented by the general formula > N-OH, -OH, -0H (where 几 is an alkyl group having 1 to 4 carbon atoms) It is immersed in an aqueous solution containing or sprayed with this aqueous solution, thereby making the aluminum or aluminum alloy surface rich in corrosion resistance, water wettability, and coating base properties.

In addition, in the process of generating an oxide film by treatment with demineralized water or distilled water, additives that promote the boehmite reaction,
For example, alkali or alkaline earth metal salts such as ammonia, monoethanolamine, jetanolamine, triethanolamine, NaOH, etc. may be added as necessary.

The temperature of the treatment with demineralized water or distilled water in this chemical conversion treatment step needs to be about 35° C. or higher.

For example, if the temperature is less than about 35°C, the formation of an oxide film on the surface of aluminum or aluminum alloy will not be sufficient. Father, the pH of the processing solution during this processing step is approximately 6 to 1.
It is preferable that it is 2. For example, if the pH is less than 6, the dissolution of aluminum will proceed faster than the formation of a film, making it impossible to obtain the desired oxide film. Also, the processing time is approximately 1
~30 minutes, particularly preferably about 3 to 20 minutes,
A preferable film can be obtained.

Moreover, the N,N-dialkylethanolamine aqueous solution is
Concentration of N,N-dialkylethanolamine i! If the concentration of N,N-dialkylethanolamine is too low, the pore-sealing effect will be weak, and conversely, if the concentration of N,N-dialkylethanolamine is too high, the film will dissolve easily and the film surface will become uneven. The concentration of ethanolamine is approximately 10-1♂ppm,
Particularly preferably, the content is in the range of 10 to 10 ppm.

Further, the treatment temperature with the N,N-dialkylethanolamine aqueous solution is preferably about 30 to 100°C, particularly preferably about 50 to 95°C, and the treatment time is about 50°C.
It is preferable to obtain a film within seconds to 10 minutes, particularly desirably about 30 seconds to 3 minutes.

In addition, N,N-dialkylethanolamine has a pore-sealing effect on the oxide film formed in the previous step, so that treatment with sodium silicate, etc., is not required, and moreover, it is less expensive than post-treatment with sodium silicate. It has excellent corrosion resistance, water wetting properties, and coating base properties.

Specific examples of the present invention will be described below.

Examples 1 to 5 JI81200-H24 aluminum alloy wrought material (50
x 1 o o x o, s w )'r: pH
After forming an oxide film on the surface of the wrought material by immersing it in distilled water of about a5 to IQ, 5, distilled water with ammonia added, or demineralized water at a temperature of 80 to 100°C for about 4 to 20 minutes, N , N
- about 60 to 95 in dialkylethanolamine aqueous solution
℃ temperature for about 1 minute.

The characteristics of the surface film of the thus treated wrought material were measured as shown in the table.

The measurement test was conducted in the following manner.

(1) Visual inspection of surface condition of formed film (2) Corrosion resistance ■Salt water spray test Salt water spray test using JT8 Z2371 After 336 hours, corrosion resistance is shown by rating number display method.

In the table, the number 1G is the best, and the smaller the number, the worse it is.

■c, h, S, s, test JIS H8681 0, A, S, S, test 9-hour ridge rating number display method shows corrosion resistance.

■Constant temperature and humidity test 4G'C, 98cs setting JJC for 24 hours and room temperature 24
After 3 cycles of aging, white rust appeared on the surface of the film. In the table, ◎ indicates no occurrence of white rust, ○ indicates occurrence of self-restraint x04 or less, and XX indicates complete occurrence of white rust.

(3) Sex The contact angle is determined using a Kyowa contact angle meter model 0A-D.

(4) Film production amount Film weight measurement using JIS Hssso.

(5) Adhesion after painting Spray paint with polyurethane paint [7. Corrosion resistance test using CASS test method, applied for 72 hours. Paint adhesion of the sample is shown using the Goban self-indication method.

As mentioned above, in the chemical conversion treatment method for aluminum or aluminum alloy according to the present invention, the surface of aluminum or aluminum alloy is treated with demineralized water, distilled water, or water to which additives are added as necessary to form an oxide film. After generating, N
, N-dialkylethanolamine solution makes it possible to carry out chemical conversion treatment of aluminum or aluminum alloys in a very short time and efficiently.Furthermore, the film produced in this way has excellent corrosion resistance, water-wetting properties, and coating properties. The adhesion after coating is extremely excellent, making it suitable for industrial materials such as heat exchanger fin materials, and furthermore, it is easy to post-process the treatment liquid during chemical conversion treatment, so it is suitable for implementing the present invention. It has the advantage of not causing any pollution problems and can be implemented at low cost.

Claims (1)

[Claims] ■ The surface of aluminum or aluminum alloy is treated with demineralized water,
Chemical conversion treatment of aluminum or aluminum alloy, characterized in that an oxide film is formed by treatment with distilled water or water with additives added thereto as necessary, and then post-treatment with an N,N-dialkylethanolamine solution. Law. ■N,N-dialkylethanolamine has the general formula,
>N-0)1. -OH, -0H (However, R has 1 carbon number
The method for chemical conversion treatment of aluminum or aluminum alloy according to claim i1, wherein the method is a chemical conversion treatment of aluminum or an aluminum alloy.