JPH0351793B2 - - Google Patents

Description

[Detailed description of the invention]

[Purpose of the Invention] (Field of Industrial Application) The present invention provides a chromate treatment method for plug welding the end of a fuel pipe made of an aluminum alloy material subjected to chromate treatment in order to improve the corrosion resistance against mixed fuel containing alcohol. It is widely used in the treatment of fuel delivery pipes for automobiles. (Prior art) As a prior art related to the present invention, a chromate treatment method is described in Aluminum Surface Technology Handbook, published on October 17, 1980, pages 69 to 271, and the composition and conditions of this conventional method are described here. are shown in Table 3. Fuel delivery pipes used in automobile engines are treated with chromate and then directly projec- tion welded onto the lid. There is a significant drop in the welding area, and fuel tends to leak from the welded area.For this reason, the chromate film at the welding location is peeled off before welding, or chromate treatment is performed after welding. (Problems to be Solved by the Invention) However, the method of chromate treatment, that is, the method of peeling off the chromate film and then welding, requires time and effort to remove the chromate film both mechanically and chemically, and furthermore, it is difficult to remove the peeled part. There is a problem of decreased corrosion resistance,
Furthermore, chromate treatment after welding poses no quality problems, but the inside of the pipe becomes bag-shaped and requires a lot of pumping out of the treatment liquid, which also makes it difficult to clean the treatment liquid inside the pipe, resulting in very high costs. The problem is that it gets high. The object of the present invention is to provide a chromate treatment solution that has strong corrosion resistance and a small amount of chromium deposit when chromate treatment is applied to a workpiece, that is, has welding strength. [Structure of the invention] (Means and effects for solving the problems) The means taken to solve the above problems are as follows. Chromate treatment is performed by adding ammonium molybdate and titanium sulfate to the composition of a conventional chromate solution. That is, in the chromate treatment method for fuel pipes made of aluminum alloy materials, the composition of the chromate treatment solution is 2 to 4 chromate anhydride.
g/L, sodium dichromate 2-3.5g/L,
Sodium fluoride 0.2-1.0g/L, ammonium molybdate 0.05, 0.15g/L, titanium sulfate 0.02
A chromate composition liquid of ~0.05 g/L and pH of 2 to 3.5 is chromated at a bath temperature of 30 to 45°C for a treatment time of 20 to 50 seconds. Due to the above chromate treatment, the amount of chromium deposited on fuel pipes made of aluminum alloy material is 40 to 200 mg/m ²
Therefore, the addition of ammonium molybdate and titanium sulfate makes the chromium adhesion layer denser, ensuring corrosion resistance even with a thin chromate film, and the welding strength is not reduced due to the thin film. No fuel leaks will occur. (Example) Specific examples will be described below. 1 is a delivery pipe used as a fuel system pipe for automobile engines, 2 is the main body, and 3
a and 3b are blind lids at both ends. The delivery pipe main body 2 is made of aluminum alloy material (JIS AD12), and after chromate treatment under the conditions shown in Table 1 for corrosion prevention purposes, blind lids 3a and 3b made of steel material (SISC) with nickel plating on both ends are installed. Excision welded.

[Table] The conditions for projection welding are the current
70KA x pressurization 1.6 tons x load time 0.15 seconds. In this case, the corrosion resistance of chromate, the strength of the welded part, and the amount of chromium deposited in the chromate film are determined by the second
Evaluation was made using the method shown in the table.

[Table] The second graph shows the chromate treatment time, corrosion resistance, welding strength, and chromium deposition amount according to Table 2.
As shown in the figure. Next, the relationship between the corrosion resistance, welding strength, and amount of chromium deposited in Table 2 and the treatment time under the conditions when the conventional chromate solution composition shown in Table 3 is used is shown in the graph of FIG. From Figures 2 and 3, the chromate treatment method of the present invention has a corrosion resistance of R/N9 under treatment conditions of 20 to 50 seconds.
With the above, welding strength of 1200 kg or more can be secured. In the conventional method, by setting the processing time to 40 seconds or more, as shown in Figure 3, corrosion resistance can be ensured at R・N9 or higher, but the welding strength is extremely low and even welding strength of 1000 kg cannot be guaranteed.

〔Effect of the invention〕

The present invention has the following unique effects. That is,
By adding ammonium molybdate and titanium sulfate to the conventional chromate treatment liquid, corrosion resistance and welding strength are increased, so there is no need to peel off some of the chromate treatment part for welding fuel pipes, making it easier to use equipment. Moreover, the number of man-hours can be reduced, and peeling other than the welded portion due to the peeling process is unlikely to occur.

[Brief explanation of drawings]

Fig. 1 is an external perspective view of an automobile delivery pipe, Fig. 2 is a graph showing the chromate treatment time, corrosion resistance, welding strength, and amount of chromium deposited according to the present example, and Fig. 3 is a graph of the conventional example. 2nd by
This is a graph similar to the one shown in the figure.

Claims (1)

[Claims] 1. In the chromate treatment method for fuel pipes made of aluminum alloy materials, the composition of the chromate treatment solution is 2.0 to 4.0 g/L of chromic anhydride and 2.0 to 4.0 g/L of sodium dichromate.
3.5g/L, sodium fluoride 0.2~1.0g/L, ammonium molybdate 0.05g~0.15g/L, titanium sulfate 0.02~0.05g/L, PH2~3.5 and bath temperature 30
Chromate treatment method: ~45℃, treatment time 20~50 seconds.