JPH0743314B2 - Test method for accelerating deterioration of coating film adhesion performance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deterioration acceleration test method for testing adhesion performance between a coating surface of a painted object and a base material.

[0002]

2. Description of the Related Art The quality of adhesion of a coating film to a substrate is directly related to the quality of rust prevention, and when the substrate is a metal, poor adhesion results in rust formation.

Generally, a salt spray test and a Cass test have been used as corrosion acceleration test methods, but they have drawbacks such as the fact that rusting is different from that caused by outdoor exposure and that there is no acceleration. Recently, as a test method to compensate for these drawbacks, a salt spray test, a hot air drying test, and a wet test were conducted in this order.
A complex corrosion cycle test, in which this series of tests is repeated as one cycle, has come to be used, and as a test method with greatly improved acceleration, it has been widely used for tests such as coating films requiring corrosion resistance. Came.

[0004] In addition, in Japanese Utility Model Publication No. Sho 62-62090,
Correlation with atmospheric exposure (outdoor exposure)
Moisture the test piece for a short time as a device to accelerate corrosion
Process and keep the air temperature at 30-40 ℃ from this state
Test with light radiant energy of infrared lamp
For repeating the process of drying the pieces for a certain time
A device is disclosed.

[0005]

In the case of the conventional composite corrosion cycle test method, the progress from the wetness of the coating film to the drying after the salt spray test is determined by, for example, drying by air heating such as blowing hot air on the test piece. Done. In this case, in the coating film test piece, the coating surface temperature and the base material temperature tended to rise in coincidence as shown in FIG.

On the other hand, in a natural environment (outdoor exposure), since the sun receives strong light (light radiant energy) for drying, the temperature of the coating surface is higher than that of the base material as shown in FIG. There is a difference, in particular, the difference is large immediately after irradiation, and the difference gradually decreases as the temperature of the coating surface rises, and both tend to have the same temperature after sunset.

Therefore, since the conventional composite corrosion cycle test method and outdoor exposure differ greatly in the drying process of the test piece, there is a significant difference in the results, particularly in the evaluation of the adhesion of the coating film to the substrate. As an example of this, for example, when a knife edge is put in the coating film and exposed outdoors, a situation occurs in which rust progresses due to peeling of the coating film in the edge portion, but the situation cannot be clearly reproduced in the complex corrosion cycle test, In addition, the phenomenon of swelling of the coating film that occurs during outdoor exposure may not be reproduced. This is because the stress in the drying process by light radiant energy is caused by the difference in the linear expansion coefficient between the base material (for example, iron plate) and the coating film (for example, acrylic resin) in the drying process by the air heating. This is because the expansion coefficient is multiplied by the temperature difference between the coating film and the base material, so that it is larger, and is several times as large as the drying by air temperature.

[0008] Also disclosed in Japanese Utility Model Publication No. 49-62090.
In the method using the device of
Since light radiant energy is applied to the
In the case of coating film test pieces, the temperature difference between the coating surface and the substrate is small.
However, it does not disappear. Therefore, in outdoor exposure, both
The conditions under which the temperatures match will not be reproducible, and complex corrosion will occur.
Similar to the food cycle test method, especially for the substrate of the coating film
In the evaluation of adhesion, there was a significant difference between the two results.
In some cases,

[0009]

[Means for Solving the Problems] To solve the above problems
In order to prevent the coating film surface of the coating film sample,
(B) Second, turn on the light source.
Light radiant energy is applied to the surface of the coating to create a space between the surface of the coating and the substrate.
The temperature of the coating surface reaches the specified temperature while causing a temperature difference.
(C) Thirdly, the temperature of the coating film surface is turned off at the same time when the light source is turned off.
Hot air at the same temperature as the
Eliminate the temperature difference between the membrane surface and the substrate, and (d) finally, wetting test
Test (Humidity 95% or more at a certain temperature between 30 and 70 ° C)
Is performed for a certain period of time (a), (b), (c), (d)
Repeat a given number of times as a series of conditions as a one-cycle test
To accelerate the swelling and peeling of the coating film and improve the adhesion performance of the coating film.
The deterioration acceleration test method of the adhesion performance of the coating film to be investigated
did.

[0010]

[Action] By adopting the above means, the coating film test
Coating film test pieces exposed outdoors during the drying process
Of the sun, that is, the strong light of the sun (radiant energy)
Since the coating film test piece is exposed to heat, the temperature of the coating surface is higher than that of the substrate.
Temperature difference between the two, and as the temperature of the coating surface rises,
The difference between the two becomes smaller little by little, and both become the same temperature after sunset.
It will be possible to reproduce the state.

[0011]

EXAMPLE As described above, the present invention conducts the salt spray test first, and secondly, while applying the light radiant energy of the light source to the coating surface to generate a temperature difference between the coating surface and the substrate. The coating surface is allowed to reach a predetermined temperature, and thirdly, the light source is turned off, and at the same time, hot air at the coating surface temperature is blown onto the coating sample for a predetermined time to eliminate the temperature difference between the coating surface and the base material while drying the test piece. And a wetting test are carried out for a predetermined time at the end, and this series of conditions is defined as one cycle and is repeated a predetermined number of times.

Specific embodiments will be described below with reference to the drawings.

FIG. 1 is a block diagram of an apparatus for carrying out the test method of the present invention. In the figure, the inside of the test tank 1 is covered by a heating tank 2 covering the test tank 1 during the salt spray test.
The coating film surface of the coating film test piece 3 installed in the test tank 1 controlled at 0 ° C. receives the atomization of 5% concentration salt water sprayed from the spray tower 4 and wets uniformly.

When a predetermined time (for example, 2 hours) programmed in the control box 5 is reached, the spray of salt water is stopped, a light source 6 (for example, an infrared lamp) arranged above the test tank 1 is turned on, and the light from the light source 6 is turned on. Radiant energy is radiated to the coating film test piece 3 and the temperature of the coating film surface rapidly rises. The temperature of the coating film surface is detected by the coating film surface temperature detecting element 7, and when it reaches a predetermined temperature (for example, 60 ° C.), the light source 6 is turned off. At the same time, the hot air in the hot air tank 8 that has been adjusted to the same temperature as the temperature of the coating surface in advance operates the blower 9 to operate the valve A.
10 is opened, and air is sent to the upper side of the test tank 1 through the hot air / humidity outlet 11 provided in the lower part of the test tank 1, and the coating film test piece 3
To dry.

When the light irradiation time plus the hot air blowing time reaches a predetermined time (for example, 4 hours) programmed in the control box 5, the valve A10 is closed and the blower 9 is stopped to stop the hot air blowing. At the same time, valve B
Open 12 and operate the humidifier 13 to open hot air / humidity outlet 1
1 sends steam to humidify the inside of the test tank 1.

The temperature in the test tank 1 is the dry-bulb temperature detecting element 14
Is performed by controlling the heating tank 2 via the control box 5 and the humidity is measured by the wet bulb temperature detecting element 15
The humidifier 13 is controlled via the control box 5 so that the wet-bulb temperature detected in 1 becomes a predetermined humidity, and a wet test condition (for example, 50 ° C., 95% RH or higher) is created and maintained.

When the wetting test is carried out for the required time, the condition of the salt spray test is re-established. The control box 5 is programmed to repeat a series of tests such as the salt spray test, the dry test (hot air blowing after light irradiation), and the wet test a predetermined number of times (for example, 15 times). Further, 16 is an exhaust pipe of this apparatus, and 17 is a drain.

Next, the relationship between the test time and the temperature in this embodiment is shown in FIG. The temperature conditions of each test are as follows: 35 ° C. in the test tank 1 when salt water is sprayed, 60 ° C. is the upper limit of the coating surface temperature by light irradiation in the first half of the drying test, and 6 is the same as the hot air blowing temperature in the second half.
The temperature in the test tank 1 is 0 ° C. and 50 ° C. in the wet test.

As described above, the temperature control in this apparatus is performed by controlling the heating tank 2 and the hot air tank 8 via the control box 5 by the signal of the dry-bulb temperature detecting element 14 in the test tank 1. During light irradiation in the first half of the drying test, the coating surface temperature detecting element 7 is switched to, and when the temperature of the coating surface reaches a preset temperature of 60 ° C., control is performed by a signal from the coating surface temperature detecting element 7. The light source 6 is turned off through the box 5, and the hot air is blown in the latter half.

[0020] Now, in FIG. 2, the coating film surface of the coating film test piece
The temperature of the base and the temperature of the base are both 3 during the salt spray test.
Agreement at 5 ° C. When the dry test is started and the light source is turned on
When light radiant energy is radiated to the coating surface, the temperature of the coating surface
The degree rises sharply. On the other hand, the temperature of the substrate rises slowly.
Therefore, a temperature difference occurs between the two. The temperature of the coating surface reaches 60 ℃
When it reaches, the light source is turned off, and at the same time, the blowing of hot air at 60 ° C
As it starts, the coating surface is maintained at 60 ℃,
The temperature also gradually rises to 60 ° C., which is the same as the temperature of the coating surface.
When the dry test is completed, the wet test is started.
When the temperature of the coating surface and the substrate are the same, the temperature drops to 50 ° C.
Down and stable.

[0021] Here, especially the coating surface during the drying test
Fig. 4 shows the state in which the temperature of the base material and the temperature of the base material shift with a temperature difference.
It was found that this corresponds to the daytime condition of outdoor exposure of
Light When exposed outdoors, at night, the coating surface and substrate
However, in the present example, the salt
In order to enhance concentration enrichment and increase test acceleration, heat
The air drying time was maintained at a high temperature for a certain period of time.
In addition, when shifting to the wet test, the test temperature (for example, 5
Outdoor exposure unless humidification is started until the temperature drops to 0 ° C)
It will be possible to reproduce the temperature drop state at night in
A temperature gradient similar to that in FIG. 4 can be obtained.

Further, since the temperature rise gradient of the coating surface depends on the light radiant energy of the light source, the light radiant energy should be increased so as to increase the light radiant energy when creating a sharp rise condition due to intense sunlight in the summer in a natural environment. Power is increased, and conversely, when a slow temperature rise condition is created by receiving weak light in winter, it is also possible to reduce the power of the light source so that the radiant energy becomes small. Although an infrared lamp is used in the embodiments, a light source for a weather resistance tester such as an ultraviolet carbon arc lamp, a sunshine carbon arc lamp, or a xenon arc lamp may be used as another light source.

[0023]

According to the test method of the present invention, when the wet state after spraying with salt water is rapidly dried by irradiation with light, a temperature difference occurs between the surface of the coating film and the substrate, and the adhesion of the coating film is large. Give physical stress. Further, the salt concentration on the surface of the coating film is rapidly concentrated. These two effects are synergistic and, for example, in a sample having a knife edge in the coating film, peeling of the coating film at the edge portion or occurrence of blistering in the coating film surface can occur.

Once peeling and swelling occur, the moisture penetrates into the peeling space between the coating film and the substrate when it is wet after drying, and the salt solution easily enters this peeling space when salt water is sprayed again. Then, during rapid drying by light irradiation and hot air drying, physical destructive force due to salt breakout is also applied, resulting in further progress of peeling of the coating film.

A coating film having good adhesion performance can prevent this progress, but a coating film having poor adhesion performance shows remarkable progress of peeling, and the difference is accelerated by the test according to the present test method. A comparison of the appearance of the test results is shown in FIGS. 6, 7 and 8.

[0026] Fig. 6 shows the results of outdoor exposure of coating film samples, and Fig. 7 shows
Salt spray (35 ° C) for 2 hours, drying with the test method of the present invention
(Light irradiation + hot air drying at 60 ℃) 4 hours, wet (50 ℃,
95% RH) 15 hours with 2 hours as 1 cycle
As a result of (120 hours), FIG.
Kuru test method, salt spray (35 ℃) 2 hours, dry (6
Only hot air at 0 ° C), wet for 4 hours (50 ° C, 95% RH)
15 cycles (120 hours) with 2 hours as one cycle
This is the result.

As a result of the one-year outdoor exposure shown in FIG. 6, a peeled portion is generated at the edge portion and two swells are observed on the coating film surface. Also in the test method of the present invention of FIG. 7, almost the same results of peeling and swelling occur. On the other hand, in the result of the conventional composite corrosion cycle test method of FIG. 8, it can be seen that slight peeling is observed, but no blistering occurs.

Therefore, according to the test method of the present invention, it is possible to obtain a result close to deterioration in outdoor exposure, and whether the adhesion performance of the coating film is good or not in a short time, for example, peeling of the knife edge portion. It is possible to accurately evaluate the size of the area, the number of swells, and the area.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for carrying out a test method of the present invention.

FIG. 2 is a diagram showing a relationship among a cycle time, temperature, and test conditions in the test method according to the example of the present invention.

FIG. 3 is a diagram illustrating a temperature relationship between a coating surface and a base material during drying by a conventional composite corrosion cycle test method.

FIG. 4 is a view for explaining a temperature relationship between a coating film surface of a coating film test piece and a substrate in outdoor exposure.

[Figure 5] The device disclosed in Japanese Utility Model Publication No. Sho 62-62090
Explain the temperature relationship between the coating surface of the coating film test piece and the substrate when used
The figure to reveal.

[Figure 6] Results of one year of outdoor exposure of coating film test pieces.

[Figure 7] Testing 15 cycles of the inventive method on coating strips
result.

[Figure 8] Conventional composite corrosion cycle test method for coating film test pieces
Test result of 15 cycles.

[Explanation of symbols]  1 Test tank  Three Coating film test piece  Four Spray tower  5 Control box  6 light source  7 Coating surface temperature detection element  8 Hot air bath  11 Hot air / humidity outlet  Thirteen humidifier  14 Dry-bulb temperature detection element  15 Wet bulb temperature detection element

Claims (1)

[Claims] 1. A coating surface of a coating film sample is (a) first subjected to a salt spray test for a certain period of time, and (b) secondly, a light source is turned on to apply light radiation energy to the coating surface. The temperature of the coating surface is made to reach a predetermined temperature while causing a temperature difference between the coating surface and the substrate, and (c) third, the light source is turned off and at the same time hot air at the same temperature as the coating surface is set to a predetermined temperature. The sample is sprayed on the coating film for an hour to eliminate the temperature difference between the coating surface and the substrate, and (d) finally, the wet test (at a certain constant temperature between 30 to 70 ° C. and a humidity of 9).
(5% or more) for a certain period of time (a), (b),
(C) and (d) A series of conditions is repeated a predetermined number of times as a test of one cycle to accelerate the swelling and peeling of the coating film, and to examine the adhesion performance of the coating film.