JP2930154B2 - Oxide film measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simply and easily measuring the thickness of an oxide film on the surface of an aluminum alloy.

[0002]

2. Description of the Related Art Conventionally, the surface of an aluminum alloy material is subjected to a surface treatment such as painting, plating, coloring treatment or the like in order to enhance corrosion resistance. From the oxide film. This oxide film becomes thicker with the passage of time, and if surface treatment such as painting is performed on the thick oxide film, defects such as pinholes and air bubbles occur between the surface treatment layer and the material surface, Moisture easily penetrates through the gap, which promotes the progress of corrosion and causes the surface treatment layer to fall off. Therefore, it is necessary to remove such an oxide film. However, the time for this treatment depends on the film thickness, and it is necessary to measure the film thickness by some method in advance. For this reason, in the related art, there are known a method of obtaining a film thickness by flowing an electric current in a plate thickness direction and measuring a resistance value at that time, and a method of calculating a film thickness by applying a laser beam and analyzing the polarization ratio thereof. I have.

[0003]

However, in the former case, the resistance value changes due to the difference in the plate thickness of the base material itself, and an oxide film is formed on the front and back surfaces of the plate. There are difficulties in terms of accurate measurement.In the latter case, the device is large and it is inconvenient to carry.For example, when the object to be measured becomes large, it is necessary to cut out a test piece and measure it. There is a problem that
For this reason, there has been a demand for a measure capable of easily and easily measuring regardless of the size of the object to be measured.

[0004]

According to the present invention, an electrolytic solution is dropped on the surface of an aluminum alloy, and a plus electrode is immersed in the dropped electrolytic solution so as to be spaced apart from the surface of the aluminum alloy by a predetermined distance. The negative electrode is connected to the base material of the aluminum alloy, a direct current is passed between the two electrodes to electrolytically separate the oxide film, and the thickness of the oxide film is determined from the completion time of the electrolytic separation. I made it. The electrolytic separation completion time was determined by measuring the time from the start of energization to the maximum current value. The spacing between the plus electrode and the surface of the aluminum alloy was maintained by bringing the positioning portion of the insulator provided on the side of the plus electrode into contact with the surface of the aluminum alloy.

[0005]

The electric power is applied to the dropped electrolytic solution to locally separate the oxide film electrolytically, and the electrolysis completion time at that time is measured by a change in the current value, and a film thickness standard according to a preset electrolysis completion time is measured. The film thickness is determined by comparing with the value sample data. At this time, since the plus electrode is held at a position at a fixed distance from the aluminum alloy surface, positioning can be easily performed by using a positioning portion provided on the side of the electrode.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for measuring an oxide film according to the present invention will be described with reference to the accompanying drawings. 1 is an overall configuration diagram of a measuring device used in the present measuring method, FIG. 2 is a partially enlarged view, and FIG.
Is a graph showing an example of a measured current value, and FIG. 4 is an example of sample data.

As shown in FIG. 1, a measuring apparatus 1 used in the measuring method of the present invention includes an anode-side probe 4 connected to a power supply 2 via a detection circuit 3, and an aluminum alloy material directly connected to the power supply 2. A cathode-side electrode rod 5 connected to W is provided, and a timer 6 having a display function is connected to the detection circuit 3.

[0008] Then, as shown in FIG.
A positive electrode 7 and a positioning bar 8 as a positioning portion provided on the side of the positive electrode 7 are provided. The positioning bar 8 is formed of an insulator and provided at, for example, a pair of left and right sides or four places around. Moreover, it is longer than the plus electrode 7 by, for example, about 0.5 mm.

For this reason, when the positioning bar 8 is brought into contact with the surface of the aluminum alloy material W, a constant interval of, for example, about 0.5 mm is always obtained between the plus electrode 7 and the surface of the material W. .

The apparatus 1 is extremely small and lightweight, can be freely carried, and can be applied to a large object to be measured.

Next, the measuring method of the present invention will be described.
The oxide film f on the surface of the aluminum alloy material W as shown in FIG.
In measuring the thickness of the material, a tartaric acid solution 10 (a solution of potassium tartrate in water) as an electrolyte solution on the surface of the material W
Is dropped.

Next, the tip of the probe 4 is inserted into the dropped tartaric acid solution 10 and the tip of the positioning bar 8 is inserted into the material W.
The positive electrode 7 is immersed in the tartaric acid solution 10 while being in contact with the surface, and is opposed to the surface of the material W at a predetermined interval of, for example, about 0.5 mm.

The negative electrode rod 5 is connected to an aluminum alloy material W. At this time, the sharpened portion at the tip is brought into contact with the back of the base material through the oxide film f.

In this state, for example, DC is applied to the plus electrode 7.
When a current of about 1 to 5 V is applied and the electric current is applied, the oxide film f in contact with the tartaric acid solution 10 starts to be decomposed into aluminum and water by an electrolytic separation phenomenon.

From this time, the current value i and the time t are measured as shown in FIG. 3. In other words, at the initial stage of the thick oxide film f, the current value i is low due to the non-conductivity of the oxide film f. As the decomposition proceeds, the conductivity increases and the current value i increases.

The time when the current value i reaches a peak is the electrolytic separation completion time T, and thereafter, the current value i decreases again with the occurrence of recoating.

The time when the current value i reaches the peak through the above process, that is, the electrolytic separation completion time T is measured, and this time is compared with previously prepared standard film thickness sample data to determine the film thickness. I do.

The standard thickness sample data is shown in FIG.
For example, in the case of aluminum GX50 material, a reference value such as a film thickness of 18 angstroms if the electrolysis completion time is 2 seconds and a film thickness of 19 angstroms if the electrolysis completion time is 3 seconds is measured in advance. It is set based on.

The measuring method of the present invention as described above is irrelevant to the size of the object to be measured and is not affected by the plate thickness. Therefore, the present invention can be applied to products such as extrusion members.

[0020]

As described above, the measuring method of the present invention is extremely compact and lightweight even when it is configured as an apparatus, and is convenient and easy to carry. Therefore, there is no need to cut out a test piece or the like, and the actual object itself can be measured in that state. Further, since there is no influence on the thickness of the sheet, there is an effect that the degree of freedom in selecting the measuring section is large.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a measuring device used in the present measuring method.

FIG. 2 is a partially enlarged view

FIG. 3 is a graph showing an example of a measured current value.

FIG. 4 is a table showing an example of sample data;

[Explanation of symbols]

 5 Negative electrode rod 7 Plus electrode 8 Positioning bar 10 Tartaric acid solution as electrolyte W Aluminum alloy material f Oxide film T Electrolytic separation completion time

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01B 7/00-7/34 102 G01B 21/00-21/32

Claims (2)

(57) [Claims] In a measuring method for measuring an oxide film on an aluminum alloy surface, an electrolytic solution is dropped on a surface of the aluminum alloy, and a plus electrode is immersed in the dropped electrolytic solution to form a surface of the aluminum alloy. And a negative electrode is connected to the base material of the aluminum alloy, and a direct current is passed between both electrodes to separate the oxide film electrolytically. A method for measuring an oxide film, wherein the thickness is obtained from a time up to a current value, and the film thickness of the oxide film is obtained from the time. 2. The method according to claim 1, wherein the gap between the positive electrode and the surface of the aluminum alloy is maintained by bringing a positioning portion of an insulator provided on a side of the positive electrode into contact with the surface of the aluminum alloy. 2. The method for measuring an oxide film according to item 1.