JPH059639A - Aluminum alloy for coating having excellent filiform corrosion resistance - Google Patents

Abstract

PURPOSE:To produce an Al alloy for coating having excellent filiform corrosion resistance by incorporating specified percentages of Mg, Si and Mn into Al and regulating the content of Fe as an impurity. CONSTITUTION:An Al alloy consisting of 0.5-1.5wt.% Mg, 0.5-1.2wt.% Si, 0.08-1.5wt.% Mn, <0.06wt.% Fe as an impurity and the balance essentially Al is prepd. About <=0.03wt.% Ti, Cr, Cu, Zr, Zn, B, etc., may be contained as other impurity elements in the Al alloy. This Al alloy for coating has excellent filiform corrosion resistance in a severe corrosive environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for coating, which is suitable for coating products used for automobile body sheet materials and the like, and has extremely excellent resistance to yarn rust even in a severe corrosive environment. The present invention relates to an aluminum alloy for painting.

[0002]

2. Description of the Related Art Conventionally, aluminum products manufactured by molding such as automobiles, trains and the like, cases for home electric appliances, etc. have a predetermined shape after molding to improve decorativeness and corrosion resistance. After surface treatment,
It is common to apply baking coating. The product which has been baked and coated in this way is subject to string-like corrosion between the material Al or Al alloy and the coating film due to surface scratches or water that penetrates through the pinholes of the paint in a severe corrosive environment during use. Thread rust may occur, causing a problem in appearance and significantly impairing product value. The occurrence of this thread rust is affected by the type of material, the pretreatment method of the material before coating, the type of coating, etc.
Although the rust corrosion is prevented by improving the chemical composition of the material, the structure, the manufacturing process, etc., the current situation is that it has not been completely solved. By the way, as an aluminum alloy conventionally used for these baking coatings,
For automobile panels, 2030 (Al-Cu type), 600
9, 6010 (Al-Mg-Si system), 5182 (Al
-Mg type) and the like, and 5182 for yarn rust resistance,
6010 and the like are said to be relatively excellent. However, car body sheet materials are
Since snowfall agents such as CaCl ₂ are often sprayed on roads as a deicing agent, the corrosive environment becomes more severe and the warranty period of automobile manufacturers has become longer. Therefore, there is a demand for development of a material having more excellent thread rust resistance.

[0003]

SUMMARY OF THE INVENTION The present invention has developed a coating aluminum alloy capable of exhibiting excellent thread rust resistance even in a severe corrosive environment as a high quality coating material in response to the above demand. ..

[0004]

In order to develop an aluminum material for coating which can achieve the above-mentioned object, the present inventor adjusted various chemical components of aluminum in order to improve the thread rust resistance of conventional aluminum materials. However, an aluminum material which has excellent thread rust resistance and can be used for vehicles such as automobiles and trains and cases for home electric appliances has been found here. The gist of the aluminum material is Mg0.5 ~ 1.5
%, Si 0.5-1.2%, Mn 0.08-1.5%, coating aluminum which is controlled to less than Fe 0.06% as impurities and the balance is substantially Al and has excellent rust resistance. It is an alloy.

[0005]

The reason for limiting the chemical components in the present invention is as follows. The additive amounts of Mg, Mn, and Si are adjusted in order to improve the thread rust resistance of the coated surface while considering strength setting and moldability according to the use as a moldable material. It was done. Mg together with Si, Mg ₂ S
A fine precipitate of i is generated at room temperature and at the time of baking coating to improve the strength. If the Mg content is less than 0.5%, sufficient mechanical performance cannot be obtained, and the Mg content should be in the range of 0.5 to 1.5% from the performance design of other additive elements. Mn prevents local corrosion, enhances general corrosion resistance, has an effect of suppressing thread rust corrosion peculiar to aluminum, and improves thread rust resistance of a coated surface. Further, Mn is an element having an effect of improving strength and formability, but if added in a small amount, it cancels out with the amount of Si. If Mn exceeds 1.5%, the moldability becomes poor, which is not preferable. Therefore, the Mn content is 0.08
The range is up to 1.5%. Si is an element that imparts strength and wear resistance, but if it is less than 0.5%, a sufficient effect cannot be obtained, and if it exceeds 1.2%, the yarn rust resistance becomes poor, which is not preferable. Therefore, the amount of Si is set to 0.5 to 1.2%. Fe is contained as an unavoidable impurity, but F
If the content of e exceeds 0.06%, the effect of the yarn rust resistance of the present invention is impaired, so the content of e is limited to less than 0.06%. Other impurity elements such as Ti, Cr, Cu, Zr, Zn, and Be may be contained if they are 0.03% or less, respectively, since they do not affect the yarn rust resistance of the present invention.

[0006]

EXAMPLE An example of the present invention will be described below.
A 50 mm thick ingot of Al alloy having the chemical composition shown in Table 1 was homogenized at 500 ° C. for 4 hours and then 480
Hot rolling was performed to a sheet thickness of 5 mm at a temperature of up to 280 ° C, and further cold rolling was performed to a sheet thickness of 1 mm. This 1 mm thick aluminum alloy plate was rapidly heated at 520 ° C., held for 10 seconds, and then rapidly cooled in water to obtain a test material. The thread rust test for the obtained test material was carried out as follows. Preparation of test piece 70 × 150 mm test piece → degreasing → surface adjustment → zinc phosphate treatment → cationic electrodeposition coating (170 ° C. × 30 minutes baking) → intermediate coating (140 ° C. × 30 minutes) → top coating (140 ° C. × 30 minutes) ) Corrosion test Using a sharp cutting edge on the coated surface, a test piece containing a straight artificial scratch (1) with a length of 25 mm and two horizontal and two horizontal lines reaching the aluminum base as shown in Fig. 1 was inserted. , Salt spray test (JI
24 hours → Wetting test (40)
C., 60 to 85% RH) 240 hours repeated test was conducted for a total of 1344 hours. Evaluation of thread rust resistance As shown in Fig. 1, thread rust is checked from the place where the artificial scratch (1) is attached.
When (2) occurs, it depends on the number of occurrences of thread rust, blistering, etc.
The evaluation was performed according to the following criteria. [Evaluation criteria for the thread rust resistance test] ○ Good without any thread rust, blister, etc. □ 〃 1 to 6 points occurred △ 〃 7 to 20 〃 × 〃 exceeds 20 points or maximum thread rust length 20 mm or more

[0007]

[Table 1]

As is clear from Table 1, all the alloys of the present invention have excellent thread rust resistance. On the other hand, all the comparative alloys having chemical components outside the scope of the present invention are inferior in thread rust resistance.

[0009]

As described in detail above, according to the present invention, an aluminum alloy having excellent thread rust resistance can be obtained by appropriately adjusting the alloy components, and it is possible to achieve a remarkable industrial effect. is there.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a thread rust test method and a situation in which thread rust is generated.

[Explanation of symbols]

 1 Artificial scratch 2 Thread rust

Claims (1)

Claims: 1. 0.5 to 1.5% by weight of Mg, Si
An aluminum alloy for coating, which contains 0.5 to 1.2% and Mn 0.08 to 1.5%, is regulated to less than 0.06% Fe as an impurity, and has the balance substantially consisting of Al and having excellent rust resistance.