JPH05126510A - Oxide layer measuring method - Google Patents

Abstract

PURPOSE:To obtain a method for measuring the thickness of an oxide layer on the surface of an aluminum alloy simply and easily. CONSTITUTION:An electrolyte 10 is dripped on the surface of an aluminum alloy W, a plus electrode is dipped into the dripped electrolyte 10 and is retained at a constant distance from the surface of the aluminum alloy W, at the same time a minus electrode 5 is connected to a base material of the aluminum alloy W, DC current is made to flow between both electrodes for enabling an oxide layer at a part which is in contact with the electrolyte 10 to be subjected to electrolytic separation. Then, by measuring the time period from the initiation of this conduction to the time when the current reaches a maximum current value, completion time of electrolytic separation is obtained and then it is compared with a reference value which is set based on a measurement data, etc., previously, thus obtaining the film thickness of the oxide layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily 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, and color development in order to improve corrosion resistance. Oxide film is generated from. This oxide film becomes thicker with the passage of time, and when surface treatment such as painting is performed on the thick oxide film, defects such as pinholes and air blow occur between the surface treatment layer and the material surface, Water easily enters through these gaps, 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, but the time of this treatment differs depending on the film thickness, and it is necessary to measure the film thickness by some method in advance. For this reason, conventionally, a method of obtaining a film thickness by measuring the resistance value at that time by passing a current in the plate thickness direction, or a method of obtaining the film thickness by irradiating a laser beam and analyzing its polarization rate is known. There is.

[0003]

However, in the former case, the resistance value changes due to the difference in the plate thickness of the base metal itself, and since the oxide film is generated on the front and back surfaces of the plate, the film thickness There is a problem in terms of accurate measurement, and in the latter case the device is large and it is inconvenient to carry.For example, when the object to be measured becomes large, you have to cut out a part of the test piece and measure it. There is a problem that does not become,
For this reason, there has been a demand for a method that allows easy and simple measurement regardless of the size of the object to be measured.

[0004]

In order to solve the above problems, the present invention is to drop an electrolytic solution on the surface of an aluminum alloy, and immerse a positive electrode in the dropped electrolytic solution so that a certain distance is left from the surface of the aluminum alloy. In this state, the negative electrode is connected to the aluminum alloy base material, a direct current is passed between the electrodes to electrolytically separate the oxide film, and the thickness of the oxide film is calculated from the completion time of this electrolytic separation. I chose Then, the electrolytic separation completion time is determined by measuring the time from the start of energization to the maximum current value. Further, the gap between the positive electrode and the aluminum alloy surface is maintained by bringing the positioning portion of the insulator provided on the side of the positive electrode into contact with the aluminum alloy surface.

[0005]

[Function] The dropped electrolytic solution is energized to locally electrolytically separate the oxide film, and the electrolysis completion time at that time is measured by the change in the current value, and the film thickness standard is set according to the preset electrolysis completion time. The film thickness is obtained by comparing with the sample data of the values. At this time, since the positive electrode is held at a position at a constant distance from the surface of the aluminum alloy, positioning can be easily performed by the positioning portion provided on the side of the electrode.

[0006]

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

As shown in FIG. 1, the measuring device 1 used in the measuring method of the present invention comprises an anode side probe 4 connected to a power source 2 via a detection circuit 3 and an aluminum alloy material directly connected to the power source 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.

The probe 4 is, as shown in FIG.
It is provided with a plus electrode 7 and a positioning bar 8 as a positioning portion provided on the side of the plus electrode 7. The positioning bar 8 is made of an insulator and is provided, for example, in a pair on the left and right, or at four locations around it. Moreover, it is longer than the plus electrode 7 by, for example, about 0.5 mm.

Therefore, 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 material W surface. ..

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.
Oxide film f on the surface of aluminum alloy material W as shown in FIG.
Tartrate solution 10 (electrolyte solution of potassium tartrate) on the surface of material W to measure the thickness of
Is dripped.

Next, the tip of the probe 4 is inserted into the dripped tartaric acid solution 10, and the tip of the positioning bar 8 is made into the material W.
The positive electrode 7 is immersed in the tartaric acid solution 10 so as to be in contact with the surface, and is faced 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 the aluminum alloy material W. At this time, the sharpened tip is brought into contact with the back of the base material through the oxide film f.

In this state, DC is applied to the plus electrode 7, for example.
By applying a current of about 1 to 5 V and applying electricity, the oxide film f in contact with the tartaric acid solution 10 begins to decompose into aluminum and water due to the electrolytic separation phenomenon.

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

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

Through the above process, the time when the current value i reaches the peak, that is, the electrolytic separation completion time T is measured, and this time is compared with the standard film thickness sample data prepared in advance to judge the film thickness. To do.

This standard film thickness sample data is shown in FIG.
For example, in the case of aluminum GX50 material, if the electrolysis completion time is 2 seconds, the film thickness is 18 angstroms, and if it is 3 seconds, the film thickness is 19 angstroms. It is set based on.

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

[0020]

As described above, the measuring method of the present invention is extremely small and lightweight even when configured as an apparatus, which is convenient and easy to carry. Therefore, it is not necessary to cut out a test piece or the like, and the actual product itself can be measured in that state. Further, since it is not affected by the plate thickness, there is an effect that there is a large degree of freedom in selecting the measuring portion.

[Brief description of drawings]

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

[Figure 2] Partly enlarged view

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

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

[Explanation of symbols]

 5 Negative Electrode Rod 7 Positive Electrode 8 Positioning Bar 10 Tartaric Acid Solution as Electrolyte W Aluminum Alloy Material f Oxide Coating T Electrolytic Separation Completion Time

Claims (2)

[Claims] 1. A measuring method for measuring an oxide film on the surface of an aluminum alloy, which comprises dropping an electrolytic solution on the surface of the aluminum alloy and immersing a positive electrode in the dropped electrolytic solution. From the start of energization, the negative electrode is connected to the aluminum alloy base material and a direct current is applied between the electrodes to electrolytically separate the oxide film. A method for measuring an oxide film, characterized in that the film thickness of the oxide film is obtained from the time until the current value and the film thickness of the oxide film is obtained from this time. 2. The holding of the space between the positive electrode and the surface of the aluminum alloy is performed by bringing a positioning portion of an insulator provided on a side portion of the positive electrode into contact with the surface of the aluminum alloy. 1. The method for measuring an oxide film according to 1.