CN1912576A - Detection method and device for thick coating adhesion force - Google Patents

Abstract

The invention relates to a detection method and a detection device for thick coating adhesion. The thick coating detection method is to apply pressure to the coating through the hole made on the substrate of the coated detection plate under simulated working conditions, so that the coating is gradually bulging and peeling off. While the coating is bulging and peeling off, measure Record coating pressure and coating peeling radius and width, or establish coating peeling radius and width-coating center bulging displacement relationship curve through numerical fitting, and indirectly measure coating peeling radius by measuring and recording coating center bulging displacement and width, and then substituted into the calculation formula of line peel strength and surface peel strength to calculate coating adhesion. The detection device for implementing the method comprises a pressurized environment simulation box, a pressure measurement and control instrument, a coating center swelling displacement measurement instrument, a detection board, a coating to be tested, a temperature measurement and control instrument and a pressurization system. The structure of the device is reasonable, and the design of the coating to be tested conforms to the real stress conditions and boundary conditions of the coating, and the detection range is wide.

Description

Thick coating adhesion detection method and detection device

1. Technical field

The invention belongs to detection methods and equipment, in particular to a detection method and a detection device for detecting the coating adhesion of powder coatings.

2. Background technology

The wide application of coating technology has opened up a new direction of material science research and application. Since the coating on the substrate can effectively change the properties of the substrate surface, not only the overall performance of the structure has been significantly improved, but also many traditional materials in It has been fully utilized in various fields of economic construction. However, the problem often encountered in practical applications is how to ensure and predict that the coating will not peel off from the substrate, otherwise, no matter how good the performance of the coating is, it cannot be used correctly and safely. Therefore, how to scientifically and accurately detect the evaluation index of coating adhesion has become an important performance index for judging the performance of coatings. The current adhesion measurement methods include tensile method, shear method, scratch method, indentation method, etc. Due to their limitations, especially for the detection of thick coatings such as powder coatings, the detection principle and results deviate from the actual coating. The force and damage are too large, and the detection data is inaccurate. Although there are many improved methods at present, there is no corresponding method and detection device suitable for thick coating adhesion detection.

3. Contents of the invention

The purpose of the present invention is to be aimed at the characteristic of powder paint coating and this coating often runs into in the course of actual use failure mode---the characteristic of bulging peeling failure, promptly owing to the penetration of medium to coating, on the coating-matrix interface Forming a bulge, due to the existence of the pressure difference, with the continuous penetration of the medium, when the bulge swells to a certain size under the pressure, the coating will slowly peel off from the substrate, thereby making the coating invalid. A thick coating adhesion detection method and detection device.

The basic idea of the present invention is: under the conditions of simulated working conditions, apply pressure to the coating through the holes made on the substrate of the coated detection plate, so that the coating is gradually bulging and peeling off, and the coating is bulging and peeling off at the same time , measure and record the coating pressure and coating peeling radius and width, or establish the coating peeling radius and width-coating center bulging displacement relationship curve through numerical fitting, and indirectly measure the coating by measuring and recording the coating center bulging displacement Peel radius and width, and then calculate the coating adhesion according to the following formula, that is, line peel strength and surface peel strength: line peel strength ${\mathrm{\&sigma;}}_l=\frac{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20051004424800092.png"\; state="\{\{state\}\}">r</figure-callout>}}{2}\mathrm{pMPa}.\mathrm{mm}---\left(1\right)$ Surface Peel Strength ${\mathrm{\&sigma;}}_b=\frac{r}{2b}\mathrm{pMPa}---\left(2\right)$

In the formula:

p-coating pressure, MPa;

r-coating peeling radius, m;

b-Coating strip width, mm.

If it is necessary to obtain the continuous change curve of coating adhesion with coating pressure, during the peeling test, measure the coating pressure and coating peeling radius and width point by point, or the coating peeling radius and width through numerical fitting ——The bulging displacement relationship curve of the coating center, measure the bulging displacement of the coating center point by point to indirectly obtain the coating peeling radius and width, and establish the coating peeling radius-coating pressure and coating peeling width-coating pressure relationship curve, and then calculate the coating line peel strength-coating pressure, coating surface peel strength-coating pressure curve according to formula (1) and formula (2).

The size of the detection hole on the detection board should be determined according to the strength of the coating material, the level of adhesion of the coating and the thickness of the coating. According to the characteristics of the coating covered on the detection hole, the coating can be assumed to be a circular plate clamped around the periphery, and the conditions for making the detection hole size are: when detecting the peeling strength of the coating line $\sqrt{\frac{{4\mathrm{Et\&omega;}}_{\max }}{(1-{\mathrm{\&mu;}}^2){\left[\mathrm{\&sigma;}\right]}_{\mathrm{coat}}}}\&le;a\&le;\frac{2}{3}\frac{{\left[\mathrm{\&sigma;}\right]}_{\mathrm{<figure-callout\; id="2"\; label="coat\; t"\; filenames="A20051004424800092.png"\; state="\{\{state\}\}">coat</figure-callout>}}{t}^{}{}^2}{{\mathrm{\&sigma;}}_l^{\&prime;}}---\left(3\right)$ Or when testing the peel strength of the coating surface $\sqrt{\frac{{4\mathrm{Et\&omega;}}_{\max }}{(1-{\mathrm{\&mu;}}^2){\left[\mathrm{\&sigma;}\right]}_{\mathrm{coat}}}}\&le;a\&le;\frac{2}{3b}\frac{{\left[\mathrm{\&sigma;}\right]}_{\mathrm{coat}}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="A20051004424800092.png"\; state="\{\{state\}\}">t</figure-callout>}}^2}{{\mathrm{\&sigma;}}_b^{\&prime;}}---\left(4\right)$

Among the above formulas:

a—radius of detection hole, mm;

E——Elastic modulus of coating material, MPa;

t—thickness of the coating to be inspected, mm;

ω _max ——the swelling displacement of the detection hole covering the center of the coating, mm;

[σ] _coat — allowable stress of coating material, mm;

σ _b ′——Estimated peel strength of coating surface, MPa;

σ _l ′——Estimated coating line peel strength, MPa.mm;

μ - Poisson's ratio of the coating material;

p——coating pressure, MPa;

At the same time, the coating pressure measuring instrument should meet:

The coating center bulging displacement measuring instrument shall meet the following requirements:

The minimum effective indication value of the displacement measuring instrument <<ω _max < the effective range of the displacement measuring instrument (6)

In order to realize this method, the coating adhesion detection device is composed of a pressure environment simulation box, a pressure measurement and control instrument, a coating center swelling displacement measurement instrument, a detection board, a coating to be tested, a temperature measurement and control instrument and a pressurization system. The pressurized system is composed of a pressurized pump, a control valve and a box connected by common hydraulic pipelines; there are detection holes on the test board and covered with the coating to be tested; the material of the test board and the material of the coating to be tested are consistent with The base material and the coating material of the tested coating adhesion parts are the same; the detection hole is set in the center of the detection plate. A detection board is provided with a large hole inlaid detection hole conversion sleeve to realize. In order to prevent paint from clogging the detection hole during coating coating, the detection hole can be equipped with a hole plug matching the size of the detection hole before coating coating. The contact surface between the hole plug and the coating is coated with a release agent. After the coating is prepared After that, remove the hole plug. The detection plate is installed on the pressure environment simulation box and is sealed and fastened with quick-opening structures such as threaded or clamped or toothed or flanged or split ring. During the test, firstly adjust the medium and temperature in the pressurized environment simulation box according to the working environment of the coating to be tested. When the temperature set by the test is reached, the pressurized system is turned on, and the coating is bulged through the test hole. Peeling pressure, during the test, the medium temperature, pressure and coating center swelling displacement in the pressure environment simulation box, as well as the coating peeling radius and width values will be detected simultaneously. If the pressure applied by the pressurization system and the temperature of the medium in the pressurized environment simulation box are controlled according to a certain change rule, the adhesion of the coating under alternating loads can be measured. After measuring the pressure exerted by the medium on the coating through the detection hole, the bulging displacement of the coating center, the peeling radius and width of the coating, it is substituted into the calculation formula of the line peel strength and surface peel strength of the coating adhesion to calculate.

The detection method is suitable for detecting the adhesion of thick coatings, the detection data is accurate, and the detection process is simple. The structure of the detection device is reasonable, and the design of the coating to be tested conforms to the real stress conditions and boundary conditions of the coating. Through reasonable configuration of the pressurization system, pressure environment simulation box, pressure and temperature measurement and control instruments, and displacement measurement instruments, the designed The stress condition of the testing coating is closer to the actual service condition of the coating; by adjusting the size of the testing hole, it is also possible to measure coatings with different thicknesses and bonding properties, and the detection range is wide.

4. Description of drawings

Fig. 1 is the structural representation of coating adhesion detection device;

Figure 2 is the coating center bulging displacement-coating pressure relationship curve;

Fig. 3 is the relationship curve of coating center bulging displacement-coating peeling radius;

Fig. 4 is the relationship curve of coating line peeling strength-coating peeling radius;

Fig. 5 is the relationship curve of coating surface peeling strength-coating peeling width.

Reference signs:

1 Pressure environment simulation box, 1-1 Environmental medium, 1-2 Pressure housing, 1-3 Evacuation valve, 1-4 Pressure maintaining valve, 1-5 Heating and heat preservation components; 2 Fastening and sealing components, 2- 1 fastening assembly, 2-2 upper flange, 2-3 seal, 2-4 lower flange; 3 pressure measurement and control instrument; 4 displacement measurement instrument; 5 detection plate; 6 detection hole; 7 detection hole conversion sleeve; 8 Coating to be tested; 9 temperature measurement and control instrument, 9-1 temperature probe; 10 pressurization system.

5. Specific implementation

Describe embodiment in detail in conjunction with accompanying drawing.

As shown in Figure 1, the pressurized environment simulation box [1] is mainly composed of an environmental medium [1-1], a pressure housing [1-2], an exhaust valve [1-3], and a pressure maintaining valve [1-4] ] and heating and heat preservation components [1-5], etc.; the fastening and sealing component [2] consists of a fastening component [2-1], an upper flange [2-2], a seal [2-3], a lower flange Composed of [2-4], the fastening component [2-1] is a set of bolts, gaskets and nuts; the pressure-bearing simplified body [1-2] and the lower flange [2-4] are welded according to the relative positions shown in Figure 1 The seal [2-3] is made of polytetrafluoroethylene gasket, placed between the test board [5] and the lower flange [2-4], the upper flange [2-2], the test board [ 5], the seal [2-3] and the lower flange [2-4] are installed in sequence, and the seal is achieved under the pre-tightening force of the fastening component [2-1]; the heating component [1-5] is composed of the jacket, The heat conduction medium, the heating jacket and the insulation jacket are used together in the position shown in Figure 1. The heat conduction medium is filled in the jacket. The heat conduction medium can be heat conduction oil or silicone oil, etc. The jacket is welded to the pressure shell [1- 2], a space filled with heat-conducting medium is formed between the inner wall and the outer wall of the pressure-bearing shell [1-2]. The entire outer wall of the jacket is wrapped by a heating jacket, and an insulating jacket is wrapped on the outer layer of the heating jacket. The heating jacket is heated by resistance set. The pressure measurement and control instrument [3] is a precision pressure gauge with a range of 0-10MPa and an accuracy of 0.25. The displacement measuring instrument [4] selects the displacement dial indicator and fixes it on the upper flange [2-2] through the displacement meter bracket. The displacement dial indicator has a range of 0-10 mm and an accuracy of 0 grade. The detection board [5] selects Q-235A, a material commonly used in engineering practice. The detection hole [6] is set at the center of the detection plate, and the size of the detection hole can be adjusted by inserting a detection hole conversion sleeve [7] in the large hole according to the strength, adhesion and thickness of the coating to be tested [8]. The coating to be tested [8] is made of powder coating. The temperature measurement and control instrument [9] is composed of a temperature control display instrument and a temperature probe [9-1]. The heating and heat preservation component [1-5] controls the circuit relay, so as to control the temperature of the ambient medium by controlling the current on and off of the heating element of the heating jacket heating and heat preservation component. The pressurization system [10] is composed of a pressurization pump, a control valve and a box. The pressurization pump can be manual or electric. For the manual pressurization pump system, the control valve may not be installed, and the electric pressurization pump is used. The system The middle control valve is connected with the control end of the pressure measurement and control instrument to control the pressure of the pressurization system. Determine whether to inlay the detection hole conversion sleeve [7] to adjust the aperture size of the detection hole [6] as required.

According to the preparation process of the coating to be tested [8], the surface of the test plate [5] is treated and the coating is prepared; according to the simulated working environment of the coating to be tested, the environmental medium is loaded into the pressure-bearing shell [1-2] [1-1]; install the gasket [2-3]; place the detection board [5] on the lower flange [2-4] and the gasket [2-3], and install the upper flange [2-2] , use the fastening component [2-1] to pre-tighten the seal; according to the simulated working temperature of the coating to be tested, set the heating temperature of the heating jacket [1-5], and heat it with electricity; after the temperature reaches the set value, close the exhaust The empty valve [1-3] pressurizes the pressure-bearing shell [1-2] through the booster pump; under the action of the pressure, the coating to be tested [8] at the hole opening will gradually bulge up, and finally the [5] was peeled off; during the test, the displacement value of the center of the coating was measured by the displacement dial indicator [4]; the pressure on the coating was read by the pressure measurement and control instrument [3].

It is difficult to measure r and b directly, and indirect measurement method, that is, finite element auxiliary analysis and fitting method is generally used. As shown in Figure 2, the specific process is as follows: First, the relationship curve of coating center bulging displacement-coating pressure shown in Figure 2 is directly measured by the actual measurement method. Secondly, take a certain pressure p and the corresponding central bulging displacement in the curve as ω; then, under the action of pressure p, use finite element analysis to calculate the central displacement value ω′ of the detection hole or the coating with a peeling radius a ;Finally, by constantly changing the peeling radius a in the finite element model, when the central displacement value ω′=ω calculated by the finite element method, the peeling radius a in the finite element model can be considered as the coating peeling radius in the actual test r. By repeating the above process, the relationship curve of coating center swelling displacement-peeling radius can be obtained, as shown in FIG. 3 .

The coating peeling bandwidth b can also be obtained by finite element analysis, but it is relatively complicated. According to experience, the strip width b of the general coating is about 0.1mm. Substitute the calculated stripping radius r and empirical stripping width b into the line

The peel strength formula (1) and the surface peel strength formula (2) can be calculated.

The peel strength of the coating can be easily measured by using the above-mentioned device. Take polyethylene (PE) as an example, its E=240MPa, μ=0.46, [σ] _coat =15MPa, σ _b ′=6MPa, b=0.1mm, the effective range of the displacement measuring instrument should be ω _max ＝0.1～ 2.51mm and take t=1mm, from the formula (4) to get 2.85≤a≤16.67mm, so it can be taken as a=4.0mm. According to formula (5) and (6), the pressure gauge and displacement dial gauge selected in the device meet the requirements.

According to the above-mentioned test and calculation steps, the measured coating center bulging displacement-coating pressure relationship curve shown in Figures 2 and 3 above and the finite element assisted analysis fitting coating peeling radius-coating center bulging displacement Relationship lines.

According to experience, it is determined that the coating peeling bandwidth b is about 0.1mm.

Correspondingly take the coating pressure, coating center bulge displacement and coating peeling radius and Substituting the width into formula (1) and formula (2), the line peel strength and surface peel strength can be calculated, as shown in Figures 4 and 5.

Through the above steps, the value of the adhesion of the PE coating is obtained to evaluate the bonding performance of the coating and the substrate.

Claims (3)

1, the thick coating adhesion force detection method, it is characterized by the bulging method, its testing process is, under the simulated condition condition, by the hole that makes on the check-out console matrix that scribbles coating, coating is exerted pressure, coating is stripped down by bulging gradually, when the coating bulging is peeled off, the survey record coating is exerted pressure and coating stripping radius and width, perhaps sets up coating stripping radius and width by numerical fitting---and coating center bulging displacement relation curve records coating stripping radius and width indirectly by the bulging displacement of survey record coating center, calculate coating adhesion, i.e. line peel strength and face peel strength by following formula then: the line peel strength ${\mathrm{\&sigma;}}_l=\frac{r}{2}\mathrm{pMPa}.\mathrm{mm}$ With the face peel strength ${\mathrm{\&sigma;}}_b=\frac{r}{2b}\mathrm{pMPa}$

In the formula:

Pressure in the p-pressure-bearing tube, MPa;

The r-disbondment radius, mm;

B-peels off bandwidth, mm.

2, a kind of thick coating adhesion force pick-up unit of implementing claim 1 detection method is characterized by this device and is made of the environmental chamber of exerting pressure, pressure testing and controlling instrument, coating center bulging displacement measuring instrument, check-out console, coating to be measured, measurement and control of temperature instrument and compression system; The hole of detection is arranged on the check-out console and cover coating to be measured; The material of check-out console and the material of coating to be measured thereof are identical with matrix material and the coating material of wanting detected coating adhesion spare; Detect the centre that the hole is opened in check-out console.

3, according to claims 2 described thick coating adhesion force pick-up units, it is characterized by described compression system is to be made of force (forcing) pump, operation valve and casing.

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