JPS61157693A - Al plate having superior suitability to phosphating - Google Patents

Abstract

PURPOSE:To obtain an Al plate having superior suitability to phosphating by forming a Zn layer, a Zn alloy layer or an Fe alloy layer on the surface of an Al plate by plating by a specified extent of deposition. CONSTITUTION:A pure Al plate or a plate of an Al alloy such as Al-Mg, Al-Cu or Al-Zn is prepd. A Zn layer, a Zn alloy layer or an Fe alloy layer is formed on the surface of the pure Al plate or the Al alloy plate by plating by >=1g/m<2> extent of deposition.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an Al or Al alloy plate having excellent phosphating properties, particularly an Al or Al alloy plate with a plating layer on the surface (hereinafter referred to as rAl alloy plate). (collectively referred to as "hill").

(Conventional technology) In recent years, there has been an increasing demand for automotive steel sheets to be protected against corrosion by spraying anti-freeze agents in cold regions, and to reduce weight in order to improve the fuel ratio. For example, they are applying surface-treated steel sheets with metal plating such as Zn or Zn-based alloy plating, or thin, high-strength high-strength steel sheets to automobile body panels.

However, the reality is that it is still difficult to say that sufficient corrosion resistance and weight reduction have been achieved.

On the other hand, it is possible to dramatically improve the above requirements by applying lightweight and corrosion-resistant Al plates made of Al or Al-gold alloys to body panels, etc., instead of conventionally used cold-rolled steel plates. However, such Al plates are only used in a small number of cases due to problems with phosphate treatment and painting clarity, which will be described later.

(Problems to be Solved by the Invention) Incidentally, on an automobile manufacturing line, generally after a body is assembled from each part, a phosphate treatment process is started. At this time, it is known that if parts made from steel plates and parts made from aluminum plates are used together in the body, problems will occur due to the formation of a phosphate film and the sharpness of the image after painting.

That is, if an Al plate is treated with a phosphate treatment bath, the Al surface will melt in the phosphate treatment bath, resulting in accumulation of A(2) ions in the phosphate bath, and all The reason for this is still not clear, but the presence of just a few ppm or more of dissolved Al ions in the bath inhibits the formation of phosphate film on the metal. It has been experimentally confirmed that the formation of a salt film rarely occurs.

In parts made of Al plates, which are inherently highly corrosion resistant, there are not many problems with regard to corrosion resistance even if a phosphate film is not formed. However, in parts made of cold-rolled steel sheets, if there is no phosphate coating, the corrosion resistance after painting will be significantly inferior, which poses an extremely serious problem. In other words, phosphate treatment is essential.

In addition, even if an Al plate is treated with phosphate, only a very small amount of phosphate film is formed, and on the other hand, a difference in surface resistance occurs between it and a cold-rolled steel plate on which a sufficient phosphate film has been formed. However, there is a problem in that the gloss and sharpness of the coating film after painting differs, which impairs the appearance.

Such difficulties are unavoidable as long as parts made of aluminum plates and steel plates are used together in the body.

Traditionally, the solution to this problem has been to add water to the phosphate bath.
, a method of adding F- ions is known.

The purpose of adding K+ and F- is to precipitate Al ions and remove dissolved Al ions using the reaction A(23" + 2K" + Na" + 6F- 2 NaAlF g (precipitate). At the same time, The purpose is to solve the above problem by making it possible to form a phosphate film on the Al plate by adding F-.

However, when processing Al plates and steel plates at the same time, the liquid composition and replenishment amount vary depending on the ratio of the areas to be treated, and in the case of a factory that manufactures many types of cars on the same phosphate treatment line, The above-mentioned area ratios are different, and it is virtually impossible to control the processing liquid components within an appropriate range.

In order to solve this problem, the present invention makes it possible to process a body having parts made of a steel plate and an aluminum plate in the same phosphate treatment line. The object of the present invention is to provide an Al plate with excellent phosphate treatment properties, which can form a phosphate film and provide image clarity comparable to that of the above-described method.

(Means for Solving the Problems) The inventors continued their intensive studies to solve the above problems, and found that they plated with an appropriate metal to completely prevent the elution of Al, and also used phosphoric acid as the metal. The present invention was completed based on the knowledge that excellent effects can be obtained by selecting a metal with excellent salt treatment property.

The gist of the present invention is to have a Zn plating layer, a Zn-based alloy plating layer, or an Fe-based alloy plating layer on the surface with an adhesion amount of 1 g/rd) d or more. Features: Al with excellent phosphate treatment properties
It is a board.

As already mentioned, there are many difficulties in applying phosphate treatment to an Al plate, and on the other hand, when directly applying a coating to an Al plate, the sharpness of the coating film is not sufficient. However, as mentioned above,
According to this invention, once a plating layer is provided and then phosphate treatment is performed in the same way as for ordinary cold-rolled steel sheets, phosphate treatment can be performed without requiring the coexistence of F- ions as in the conventional method. Moreover, the paintability obtained is comparable to that of cold-rolled steel sheets.

That is, A having excellent phosphate treatment properties according to the present invention
l plate has a Zn plating layer of 1 g/m or more on the surface, Z
It is equipped with either an n-based alloy plating layer or an Fe-based alloy plating layer, and the steel plate forming the base includes not only pure Al plate but also various Al alloy plates. A
Typical examples of l-alloy plates include Al--Mg based, Al--Cu based, and Al=Zn based high-strength rolled materials that are widely used in automobiles today.

In this invention, the plating layer formed on the Al plate includes a Zn plating layer, a Zn-based alloy plating layer, for example, a Zn
-Fe, Zn-Co, Zn-Ni, etc., there are Fe-based alloy plating layers, such as Fe-5b, and any one of them is formed on the steel plate by a known electroplating or dip plating method. Therefore, the plating conditions and plating composition are not particularly limited, and according to the experiments conducted by the inventors, satisfactory results were obtained in all of them under normal plating conditions and plating composition.

As described above, the reason why the plating layer is formed on the Al plate in this invention is to prevent the dissolution of Al in the phosphate treatment solution in the plating layer, and also to prevent the coating from dissolving in the phosphate treatment solution. By making the composition Zn, Zn-based alloy, or Fe-based alloy, a phosphate film can be formed even on an Al plate. In other words, it is possible to form a phosphate film to the same extent as on cold-rolled steel sheets. Therefore, in that case, the plating amount is set to be Ig/m' or more because the plating amount is 1g/m' or more.
If it is less than g/rd, it will not be possible to prevent Al dissolution in the base material, and Al dissolution will occur in excess of the amount of plating deposited, resulting in A in the bath.
This is because the l ion concentration increases, which not only impairs the formation of a phosphate film on the surface of the steel plate, but also prevents the formation of a phosphate film on the Al plate. On the other hand, in the present invention, there is no particular upper limit to the amount of plating deposited, but if it is too thick, workability will be impaired, so from the viewpoint of cost etc., the upper limit is usually preferably 5 g/'rd or less.

Thus, by forming the plating layer on the Al plate as described above, the dissolution of Al in the phosphate treatment solution is effectively prevented, and the plating film itself is melted, resulting in the same phosphorus formation as in cold-rolled steel. This allows formation of an acid salt film.

Therefore, according to the present invention, phosphate treatment of products and parts that use both Al plate and cold-rolled steel plate can be carried out on the same line with a treatment liquid having the same treatment liquid components, and the sharpness of the coating film after painting can be improved for both. You can get something without any difference.

Next, the present invention will be explained in further detail by way of examples.

Example Sample material A shown in Table 1 (Magnets 1 to 3, N15 to 8 are Al single plates, Magnet 4 is 8Q99%-Mg 1% Al alloy plate, Dial 9 is CO, 05%-Mn 0 .25% cold-rolled steel plate), test 11hl Al plate and Na9 cold-rolled steel plate specimens were left unplated without plating, and test materials 11h2 to 8 were as shown in the same table. Plating bath composition (sulfate bath), bath p
Zn plating, Zn-based alloy plating, and Pa-based alloy plating were performed at H1 plating current density, and the surfaces thereof were plated with the plating layer composition shown in the left column of the same table. The Al plate sample material of Test 11h2 was coated with plating with a coating weight of 0.5 g/rrr, which is outside the scope of this invention.
The amount of plating deposited on the Al plate sample material was 1.5 g/n, which is within the scope of this invention. The plating of Test-4 Al-Mg
After forming plating with a plating weight of 5 g/m on the Al alloy plate sample of Test N115-8, and plating with a plating weight of 3 g/rrf on the Al plate sample of test N115-8, commercially available phosphoric acid was applied. Phosphate treatment was performed by immersing each sample material for 2 minutes under standard conditions using a salt treatment agent (trade name "Granozinc", manufactured by Nippon Paint Co., Ltd.). The results obtained are summarized in Table 2. The left column of Table 2 shows the amount of phosphate deposited on the surface of each sample material A shown in Table 1 that was phosphate treated immediately after preparation of the treatment solution, and the right column of the same table. For each sample material, treat liquid II! , per 0.5
The figure shows the amount of phosphate deposited on the surface of the surface when it is continuously treated at a rate of rrf and the Al ion concentration in the treatment solution at that time.

In addition, Alt5. of test positions 1 to 8. Alternatively, in the case of continuous treatment of Al alloy plates, when a cold-rolled steel plate (same as sample material No. 9 in Table 1) was further treated with the treatment solution, the amount shown as sample material B in the table was The amount of phosphoric acid deposited was obtained.

In the case of the present invention, there was virtually no difference in the amount of phosphate deposited even when the test materials were treated one after another. In other words, in the case of the example of the present invention, the amount of eluted Al ions is t ppm or less, and has no effect on the phosphate treatability.

Table 3 shows the test samples that were treated with phosphate immediately after bath preparation.

A commercially available Power Top U-30 manufactured by Nippon Paint Co., Ltd. was cationically electrodeposited to a thickness of 20 μm on sample material A and the above-mentioned sample material B when treated with material A at 0.5 m/l. Intercoated with 25 μm thick OTO4810 gray manufactured by the same company! ! The results of examining the clarity of the coating film after overcoating with OTO626 white to a thickness of 30 μm are shown.

Here, "sharpness" refers to the sharpness glossiness needle (Tokyo type knee PG).
D-2I-7794).

From the results shown in Tables 3 and above, Tables 2 and 3, in the case of the sample material of Test 1, which is a comparative example, that is, a single Al plate treated with phosphate without plating, immediately after bath construction, Even after the 0.5rJ/J treatment, the amount of phosphate deposited was 0.1g/rd in both cases, and almost no phosphate crystals were formed, and on the contrary, Al
is melted and after 0.5 rrr/1 treatment, 50
ppm of Q ions are dissolved, so with this treatment solution,
Even if a cold-rolled steel sheet is treated, which should originally generate sufficient phosphate crystals, the amount of phosphate deposited on the surface is only 0.5 g/rrr due to the high Al ion concentration. No crystals are formed. Therefore, in both cases, the image clarity after painting is poor.

The sample material of Test 11h2, which is a comparative example, that is, 0 on the Al plate.
．． 5 g/rrrFe-Zn plating is applied, immediately after bath preparation when the Al ion concentration is low, a certain amount of phosphate crystals are generated due to the effect of the plating layer, and the image clarity after painting is not bad. However, the melting of Al cannot be completely prevented, and the shark ion concentration increases depending on the amount of treatment, resulting in a decrease in phosphate treatment properties. 8ppm after 0.5%/J treatment
As a result, similar to the above, sufficient phosphate crystals are not formed in the cold-rolled steel sheet, resulting in poor image clarity after coating.

On the other hand, the test materials of Test Cases 3 to 8, which are examples of the present invention, that is, the Al plates or Al alloy plates plated with a plating of Ig/d or higher, prevent the dissolution of Al due to the plating effect. As the bath temperature increases, a sufficient amount of phosphate film is easily generated, and the phosphate treatment property does not decrease even after the 0.5%/N treatment, and the Al ion concentration remains at lpp, the same as after bath preparation.
m or less, and the Al plate or Al alloy plate is 0.5 m
/7! Almost the same amount of phosphate crystals are generated in the cold-rolled steel sheet treated with the treated solution as in the case of the Al sheet or Al alloy sheet. This is comparable to that of the cold rolled steel plate of Test No. 9, which is a comparative example, which was subjected to continuous treatment. therefore,
The image clarity after painting is also excellent, and there is no difference between Al plate or Al alloy plate and cold rolled steel plate.

Note that the test scores are the same throughout Tables 1 to 3.

Claims (1)

[Claims] Zn plating layer, Zn alloy plating layer, or Fe on the surface
One of the plating layers of the alloy plating layer is 1 g/m^
An Al plate with excellent phosphate treatment properties, characterized by having a coating weight of 2 or more.