JPS5952718B2 - Two-step sealing method for anodic oxide film on aluminum or aluminum alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for sealing an anodized film of aluminum or an aluminum alloy (hereinafter simply referred to as aluminum).

Generally, aluminum is subjected to a sealing treatment to prevent surface contamination, improve corrosion resistance, and protect and stabilize the colorant applied to the oxide film after anodizing.

Conventionally, methods for sealing include (a) a pressurized steam method in which the anodic oxide film is treated with pressurized steam of 3 kg/- or more for 20 minutes or more, and (1) the anodized film is immersed in boiling water at a temperature of 98°C or more. Boiling water method, which involves soaking for 15 minutes or more.
(--) A metal salt method in which the anodized film is treated by immersing it in a heated aqueous solution in which a large amount of a hydrolyzable metal salt, especially nickel acetate or cobalt acetate, is dissolved; The silicate method, which involves immersing the anodic oxide film in a heated aqueous solution of sodium silicate (water glass), has been implemented. ing.

However, the conventional pore sealing method described above has various drawbacks as follows.

In other words, the pressurized steam method (a) is one of the methods that has been widely used in the past, and although the properties of the sealed anodic oxide film are quite good, it is not suitable for mass production, and the equipment cost is high. However, they are expensive and are not particularly suitable for processing large aluminum parts; for this reason, the boiling water method or metal salts immersed in heated aqueous solutions such as nickel acetate (-) are expensive. law is being practiced. However, although the boiling water method is simple, it has the disadvantage that the sealing effect is not sufficient, while the metal salt method has a better sealing effect than the boiling water method, but
However, it is insufficient, and white powdery precipitates often occur on the sealing surface, which must be removed by methods such as para-polishing, resulting in the necessity of such a finishing process and the difficulty of bath management. In addition, the high cost of raw materials increases the product price, and the method of dipping in dichromate or chromate aqueous solution has the disadvantage of leaving a yellow color on the product. Although the method of dipping in a sodium silicate aqueous solution improves the corrosion resistance of the film, it is less effective than other treatment methods, and the adhesion of the paint during painting is poor.This invention is a sealing method for aluminum anodic oxide film that solves the drawbacks of the conventional methods mentioned above, not only has an excellent sealing effect, but also allows easy management of the treatment bath and can be carried out at low cost with simple equipment. It provides a treatment method, specifically, by treating anodized aluminum with common sealants such as metal salts, ammonium derivatives, alkali hydroxides, amine compounds, or boron compounds at room temperature or slightly heated. (hereinafter referred to as first sealing), and then immersed in heated tap water, well water, industrial water, or ion-exchanged water (hereinafter referred to as second sealing),
The above object has been achieved by such a two-stage sealing method. In the case of the present invention, among the sealing agents that can be used in the first sealing treatment, examples of metal salts include nickel,
Nitrates, sulfates, acetates, etc. of cobalt, lead, chromium, etc. are suitable, and ammonium derivatives include, for example, aqueous ammonia, hydrazine hydrate, hydrazine sulfate, etc.
Examples of alkali hydroxides include sodium hydroxide and potassium hydroxide; examples of amine compounds include diethylethanolamine and triethanolamine; examples of boron compounds include ammonium borate, potassium borate,
Sodium metaborate, etc. can be used, and other commonly used sealants are also effective, and waste liquid from inorganic coloring baths containing metal salts such as nickel or boron compounds such as boric acid can also be used. .

The concentration used is 0.1 g/l to saturation concentration, the bath temperature for the first sealing is 5°C to 80°C, and the bath temperature for the second sealing is 60°C to 100°C. . in this case,
At a concentration of 0.1 g or less, the effect is weak, and as the concentration increases, the effect becomes more pronounced. However, it is not economical to use something too concentrated, and for practical purposes it is 0.1g/l to 50g.
/l is appropriate. At this time, the higher the temperature of the first sealing, the better the effect, but normal temperature is usually sufficient. In addition to the ion-exchanged water conventionally used in boiling water sealing, tap water, well water, or industrial water can be used for the second sealing, and the effect is weak at temperatures below 60°C. The higher the temperature, the more pronounced the effect. From this point of view, as a practical condition, the additive concentration in the first sealing hole is 0.1 to 50.
The temperature is preferably room temperature (10~30℃), and tap water, well water, or industrial water is used for the second sealing, and the temperature is 60~30℃.
It is desirable to process at a temperature of 100°C. Next, examples of the hole sealing method according to the present invention will be described.

Extruded aluminum profile (A6O) with conventional pretreatment
63S-T5) as an anode, it was immersed in a 15% (weight ratio) sulfuric acid aqueous solution (temperature 20°C), and the current density was 1.3A/D.
After performing anodizing treatment for 30 minutes at m. The sealing effect was evaluated for those that were dried after drying and those that were sealed in conventional boiling water.

The results are summarized and charted below. The sealing evaluation was performed based on the appearance after sealing treatment, an alkali resistance test, a cast test (JISH86Ol), an anthraquinone violet dye dyeing sewage test, a painting test, etc.

According to the above test results, the higher the sealing agent concentration in the first sealing hole, the better the corrosion resistance in alkali resistance, cast tests, etc.
It can be seen that the other properties of the pores sealed by the treatment method of the present invention are generally superior to those of the conventional treatment method.

The inventors of the present invention attempted to seal the anodic oxide film on pure aluminum and other aluminum alloys in addition to extruded aluminum profiles, but obtained results similar to those in the above examples. As described above, when the method of the present invention is applied to the sealing treatment of anodized aluminum coatings, the surface of the sealed coating is extremely clean and has no coloration, and excellent sealing results can be obtained in a short time. In addition, the adhesion of the paint is very good, and the treatment itself is extremely easy and can be done at low temperatures, and the aging of the bath is minimal, making it an inexpensive treatment method.

Claims (1)

[Claims] 1. After forming an anodic oxide film on aluminum or aluminum alloy, one of the commonly used sealants such as metal salts, ammonium derivatives, amine compounds, alkali hydroxides, or boron compounds is used as the first sealing treatment. or more in the range of 0.1/l to saturation concentration 5 to 80
℃ immersion in an aqueous solution, then 60-1 as a second sealing.
A two-step sealing method for an anodized film of aluminum or aluminum alloy, which comprises immersing it in water heated to 00°C.