Method for detecting scratch resistance and gouges resistance of automobile coating

Abstract

The invention discloses a method for detecting scratch resistance and gouges resistance of an automobile coating. The detection method comprises the following steps: according to the requirements of a coating process, coating of each coating is sprayed on an electrophoresis plate to obtain an automobile coating, n disconnected cutting areas are cut on the electrophoresis plate by using a cutter, the cutting areas are required to be the same in size, the automobile coating is scraped off, a rectangular area of the electrophoresis coating is exposed, and a test sample plate is obtained; a cylindrical pencil lead of a test pencil is pressed downwards on the scribing line of any scribing area at the angle of 44-46 degrees under the load of 14-16 N, and the pencil is pushed at the scribing and pushing speed of 2-4 mm / s in the direction perpendicular to the scribing line until the cylindrical pencil lead is broken or the exposed cylindrical pencil lead is completely abraded; the scratch-resistant and gouge-resistant performance of the automobile coating can be quickly and accurately judged by recording the cutting length of the test pencil, and screening of formulas in the initial stage of paint development is effectively dealt with, so that the complaint of paint film damage caused by collision of automobile assembly is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile coating detection and evaluation, and more specifically, to a method for detecting the scratch resistance and dent resistance of automobile coatings. Background Art

[0002] With the continuous improvement of people's living standards and the tremendous progress of the automotive industry, cars have become an essential consumer product and means of transportation. The manufacturing process generally goes through the following steps: sketching - mold making and assembly - circuit design - manufacturing and welding - painting - vehicle assembly - beautification and commissioning. After the various parts of the car are painted, the whole vehicle assembly process will inevitably suffer from bumps and scrapes from tools, walls, and machine edges. If these bumps and scrapes cause coating peeling and other problems attributed to poor coating performance, the car company will complain to the paint company at the next level and report the relevant issues. At this time, it may be difficult for the paint company to adjust the paint formula to improve the coating's resistance to bumps and scrapes. If remedial measures are not taken in a timely manner, the paint company may lose orders, resulting in huge financial losses.

[0003] In the past, when coatings were developed, there were almost no means of testing the coating's resistance to bumps and scratches. The only tests on paint film strength in the national standards include the GB / T6739 pencil method for determining paint film hardness, GB / T9286 and GB / T1720 for determining paint film adhesion, and GB / T1732 for determining paint film impact resistance. However, in fact, the hardness, adhesion, and impact resistance of the paint film are different from the bump and scratch resistance of the paint film. A paint film with high hardness, good adhesion, and good impact resistance does not necessarily mean that it has bump and scratch resistance and can resist bumps and scratches during vehicle assembly. In addition, these national standard tests still require professional instruments for verification, and have poor operational flexibility.

[0004] In view of this, it is necessary to develop a test method for the scratch resistance of automotive coatings. This test method, as a supplement to the automotive coating strength test method, can more quickly screen formulas in the early stages of coating development, improve coating development efficiency, and predict complaints caused by paint film damage due to assembly bumps in advance, so that timely adjustments can be made to the paint film to reduce unnecessary economic losses. Summary of the Invention

[0005] In response to the demand for scratch resistance in coatings on various parts of automobiles, the present invention aims to provide a method for testing the scratch and dent resistance of automotive coatings. This intuitive observation of scratch length allows for rapid and accurate assessment of the scratch and dent resistance of automotive coatings. This facilitates the elimination of inappropriate coating formulations during the early stages of coating development, thereby avoiding complaints later related to paint film damage caused by bumps and dents during vehicle assembly, and indirectly improving the efficiency of automotive coating development.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a method for detecting the scratch resistance and scratch resistance of automobile coatings, comprising the following steps:

[0008] 1) Preparing a test pencil: Obtain a pencil with a flat cylindrical pencil tip as a test pencil, wherein the exposed length of the cylindrical pencil lead at the pencil tip is 2-4 mm;

[0009] 2) Preparing a test panel: According to the coating process requirements, spray each coating layer onto an electrophoretic plate to obtain an automotive coating. Use a cutter to create n unconnected cut areas on the electrophoretic plate, where n is an integer greater than or equal to 4. Each cut area must be a rectangular area of ​​the same size, scraped off the automotive coating layer to expose the electrophoretic coating layer, to obtain a test panel.

[0010] 3) Press the cylindrical lead of the test pencil downward on the score line of any score area at a 44-46° angle under a load of 14-16 N. Push the pencil perpendicular to the score line from the score area toward the non-score area containing the automotive coating at a speed of 2-4 mm / s until the cylindrical lead breaks or the exposed cylindrical lead is completely worn away. Record the length of the score in the non-score area.

[0011] 4) Repeat step 3) to test other scribing areas and record the scribing lengths.

[0012] Furthermore, when the scratch length of the scratched area accounting for more than 75% of the total scratched area is ≤5 mm, it is determined that the automotive coating has the ability to resist scratches and scratches.

[0013] Furthermore, the exposed length of the cylindrical pencil lead is 3 mm.

[0014] Furthermore, the pencil is selected from Mitsubishi drawing pencils, model "UNI" F.

[0015] Furthermore, the automobile coating is selected from one or more of a mid-coat, a color paint layer, and a clear coat layer.

[0016] Furthermore, the length of the cut area is 8-12 mm, and the width is 1-3 mm.

[0017] Furthermore, the n is 4.

[0018] Furthermore, in step 3), a cylindrical pencil lead of a test pencil is pressed downward on a scoring line of any scoring area at an angle of 45° under a load of 15N.

[0019] Furthermore, the rowing speed is 3 mm / s.

[0020] Furthermore, the test pencil is obtained according to the following steps:

[0021] Use a pencil sharpener to remove the wood covering the pencil lead, then use sandpaper to polish the tip of the pencil lead to obtain a flat cylindrical pencil tip, and finally obtain a cylindrical pencil lead of 2-4 mm to obtain a test pencil;

[0022] Wherein, the particle number of the sandpaper is above 400.

[0023] The beneficial effects of the present invention are as follows:

[0024] The detection method provided by the present invention can quickly and accurately judge the strength of the automobile coating, that is, the scratch and bump resistance performance, by scratching (cutting) the length of the coating film on the automobile coating with a pencil, thereby quickly and effectively responding to the screening of the coating formula in the early stage of development, avoiding complaints caused by paint film damage caused by bumps during automobile assembly, and indirectly improving the development efficiency of automobile coatings.

[0025] The detection method provided by this invention is applicable to coating systems using various coating processes, such as 3B2B, 3C1B, IPP, and CCT. Adjustments are required based on the actual coating process requirements. The detection conditions are simple and easy to implement, closely resembling actual usage scenarios. This method allows for rapid and effective verification of the scratch and dent resistance of actual automotive coatings. Statistical results show that automotive coatings that pass the inspection using this method have experienced virtually no complaints of paint damage due to dents within a 1-5 year assembly period. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] Figure 1 A schematic diagram of a test sample used in the detection method of the present invention is shown.

[0028] Figure 2 A schematic diagram of a test pencil used in the detection method of the present invention is shown.

[0029] Figure 3 A schematic diagram showing the swiping direction in the detection method of the present invention is shown. DETAILED DESCRIPTION

[0030] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0032] The scratch and scratch resistance of the automotive coating in the present invention refers to whether more serious problems such as peeling and cracking of the automotive coating will occur when the automotive coating is bumped and scratched during vehicle assembly in a car factory. An automotive coating with strong scratch and scratch resistance will not cause more serious problems such as peeling and cracking of the automotive coating due to the overall damage of the paint film after being bumped and scratched. An automotive coating with poor scratch and scratch resistance will cause more serious problems such as peeling and cracking of the automotive coating due to the overall damage of the paint film after being bumped and scratched, which are judged as poor coating quality.

[0033] Since there is no method for evaluating the scratch resistance and scratch resistance of automobile coatings in the prior art, the present invention discloses a method for detecting the scratch resistance and scratch resistance of automobile coatings, comprising the following steps:

[0034] 1) Prepare the test pencil: Use a pencil sharpener to remove the wood covering the lead, being careful not to damage the lead core. Then, use sandpaper to polish the tip of the lead to a smooth cylindrical tip. The final result is a 2-4 mm cylindrical lead, which is the test pencil.

[0035] To ensure consistency in the pencils used throughout the testing method, it is important to ensure that the pencils are sourced from the same source. Even pencils produced by different manufacturers may have different lead strengths, even if they have the same hardness. Furthermore, the preparation method for the pencils must be uniform. This is to ensure consistency in terms of the exposed length, exposed condition, and polished tip of the pencil lead. Therefore, the pencil sharpening method described in GB / T 6739, the pencil method for determining paint film hardness, was used for preparation.

[0036] The pencil used in the present invention is a Mitsubishi drawing pencil, model "UNI" F. Technicians will understand that the detection method developed in the present invention is based on the Mitsubishi drawing pencil "UNI" F. On the basis of the technical solution of the present invention, the pencil manufacturer and model can also be changed to develop corresponding detection conditions. No specific limitation is made here, and all are within the scope of protection of the present invention.

[0037] 2) Preparing a test panel: According to the coating process requirements, spray each coating layer onto an electrophoretic plate to obtain an automotive coating. Use a cutter to create n unconnected cut areas on the electrophoretic plate, where n is an integer greater than or equal to 4. Each cut area must be a rectangular area of ​​the same size, scraped off the automotive coating layer to expose the electrophoretic coating layer, to obtain a test panel.

[0038] When preparing the test samples, the coating application conditions should be consistent with those of the vehicle factory assembly line, that is, the coating formula, coating combination, and spraying parameters should be consistent. Coating processes such as 3B2B, 3C1B, IPP, and CCT commonly used by various vehicle factories are all applicable to this test method.

[0039] 3) Press the cylindrical lead of the test pencil downward on the score line of any score area at a 44-46° angle under a load of 14-16 N. Push the pencil perpendicular to the score line from the score area toward the non-score area containing the automotive coating at a speed of 2-4 mm / s until the cylindrical lead breaks or the exposed cylindrical lead is completely worn away. Record the length of the score in the non-score area.

[0040] During the scratching and pushing operation, the tip of the pencil lead is located at the junction of the scratching area and the non-scratching area. The two areas are separated by the scratching line and have a certain height difference. The flat surface formed by the polished tip of the pencil lead is against the outer edge of the non-scratching area containing the automobile coating. If extrusion and extrapolation are performed perpendicular to the scratching line, the automobile coating will be subjected to external forces from the extrusion and tearing of the pencil lead tip. Under the action of external forces, the automobile coating may be torn and damaged, resulting in a certain scratching length. It is also possible that the automobile coating cannot be torn and damaged under the load of a limited force, no scratching length is generated, and even the pencil lead may break. This method can be used to judge the scratch and bump resistance of the automobile coating. The shorter the scratching length, the stronger the automobile coating's ability to resist external force extrusion and tearing, and the stronger its scratch and bump resistance.

[0041] It should be noted that the external forces exerted on the automotive coating by the pencil tip during this testing method differ from the external forces exerted on the paint film by the pencil tip during the paint film hardness determination method according to GB / T 6739. This is due to the following reasons: first, the location of the force: in GB / T 6739, pencils of varying hardness are used to scratch the paint film surface, while the present invention scratches and pushes the paint film from the side. Second, the magnitude of the force differs: the magnitude of the force here refers not to the force exerted by the pencil, but to the force exerted by the paint film to prevent the pencil from sliding. In GB / T 6739, the front of the paint film is in contact with the pencil tip, and the surface resistance is usually smooth, resulting in relatively little resistance. In contrast, in the present invention, the resistance is significantly greater due to scratching and pushing the paint film from the side. Third, the type of force differs: in GB / T 6739, scratching the paint film with a pencil only results in sliding friction, while in the present invention, scratching and pushing the paint film from the side results in not only sliding friction but also a combination of forces, such as the film's reverse thrust and interlayer adhesion. This combination of forces is beneficial for better evaluating the scratch and dent resistance of automotive coatings.

[0042] 4) Repeat step 3) to test other scribing areas and record the scribing lengths.

[0043] Furthermore, when the scratch length of the scratched area accounting for more than 75% of the total scratched area is ≤5 mm, it is determined that the automotive coating has the ability to resist scratches and scratches.

[0044] Furthermore, the exposed length of the cylindrical pencil lead is 3 mm.

[0045] Furthermore, the automobile coating is selected from one or more of a midcoat, a color paint layer, and a clearcoat layer. For example, the automobile coating can be a composite coating combination of a midcoat + a color paint layer + a clearcoat layer, a composite coating combination of a midcoat + a color paint layer, a composite coating combination of a color paint layer + a clearcoat layer, a single coating of a pure color paint layer, and the like.

[0046] Furthermore, the length of the cutting area is 8-12 mm and the width is 1-3 mm. For example, the cutting area can be a rectangular area with a length of 10 mm and a width of 2 mm, and the edges of the rectangular area are the cutting lines.

[0047] Considering various factors such as experimental contingency, accuracy and experimental cost, it is appropriate to limit the number of divided areas to 4.

[0048] Furthermore, in step 3), a cylindrical pencil lead of a test pencil is pressed downward on a scoring line of any scoring area at an angle of 45° under a load of 15N.

[0049] Furthermore, the rowing speed is 3 mm / s.

[0050] In order to ensure the flatness of the end surface of the cylindrical pencil lead, it is also necessary to limit the fineness of the sandpaper used to grind the pencil lead. Normally, sandpaper with a grain size of 400 or above can be used.

[0051] Materials and equipment involved in the embodiments of the present invention:

[0052] 1. Matching electrophoresis plate;

[0053] 2. Matching primer, basecoat and clearcoat;

[0054] 3. Spray gun;

[0055] 4. Oven;

[0056] 5. Pencil;

[0057] 6. Utility knife;

[0058] 7. Ruler.

[0059] Example 1

[0060] Using the scratch and mar resistance testing method for automotive coatings described in the present invention, a composite coating consisting of a water-based basecoat AR-2100NH-730, its matching midcoat AR-830N2, and a clearcoat MAC O-1900 was tested to determine the scratch and mar resistance of the composite coating consisting of the midcoat + water-based basecoat + clearcoat.

[0061] The specific steps include the following:

[0062] Step 1: According to the coating process requirements, spray the intermediate paint AR-830N2, water-based base paint AR-2100NH-730 and clear paint MAC O-1900 on the 70mm*150mm electrophoresis plate in sequence, and then dry in an oven to obtain the automotive coating;

[0063] Among them, the water-based base paint coating process requirements are atomizer ACCU707 (65mm), stroke distance curve 95mm, running speed 500mm / min, speed 45krpm / min, voltage -75kv, spraying distance 250mm, discharge volume 95+95ml / min, film thickness 10-11μm, and the mid-coat coating process requirements are atomizer ACCU707 (50mm), stroke distance curve 100mm, running speed 500mm / m in, speed 55krpm / min, voltage -75kv, spray distance 250mm, discharge volume 200ml / min, film thickness 18-20μm, varnish coating process requirements are atomizer ACCU707 (50mm), stroke distance curve 85mm, running speed 500mm / min, speed 50krpm / min, voltage -75kv, spray distance 200mm, discharge volume 245ml / min, film thickness 36-39μm;

[0064] Step 2: Use a 0.4mm thick utility knife to cut the car coating in the middle area of ​​the electrophoretic plate sprayed with the car coating. It is required to cut out 4 unconnected cut areas. Each cut area is required to be a rectangular area with a length of 10mm and a width of 2mm. All water-based paint, mid-coat and clear coat should be scraped off in the cut area to expose the electrophoretic coating film to obtain the test sample. Be careful to clean the car coating debris in the cut area. See Figure 1 ;

[0065] Step 3: Use a Mitsubishi drawing pencil, model "UNI" F, certified and issued by the Japan Paint Inspection Association. Use a pencil sharpener to remove the wood covering the pencil lead, exposing the pencil lead. Then use sandpaper (grit size 400) to polish the tip of the pencil lead to a flat cylindrical tip approximately 3 mm thick, thus obtaining a test pencil.

[0066] Step 4: See Figure 2 and Figure 3 , use the cylindrical pencil lead of the test pencil to hold the pencil under a load of 15N and press it downward at a 45° angle on the cut line of any cut area (either the long side or the short side). Push the pencil from the cut area to the non-cut area containing the automotive coating at a speed of 3mm / s in a direction perpendicular to the cut line until the cylindrical pencil lead breaks or the exposed cylindrical pencil lead is completely worn away, and the automotive coating in the non-cut area is damaged under the pushing force of the test pencil. Record the length of the cut in the non-cut area;

[0067] Step 5: Use a ruler to measure the scratch length. When the scratch length of three or more of the four scratch areas is ≤5 mm, the composite coating is judged to be scratch-resistant and resistant to scratches, and the paint film is not easily damaged during assembly. The results are shown in Table 1.

[0068] Table 1 Test results of composite coating scratch resistance and scratch resistance

[0069]

[0070] The above experimental results show that after the composite coating was tested using the testing method of the present invention, the scratch lengths in the four scratch areas were all within 3.5 mm. This indicates that the composite coating of this color is scratch-resistant and resistant to scratches. Subsequent tracking data indicates that during the five years of assembly operations at customer sites for this color, there was no complaint of damage to the paint film due to bumps.

[0071] Example 2

[0072] Using the scratch and mar resistance testing method for automotive coatings described in this application, a composite coating consisting of a water-based base paint AR-3500NH-821M and its matching clear coat Mac O-1900 was tested to determine the scratch and mar resistance of the composite coating consisting of the water-based base paint + clear coat.

[0073] The specific steps include the following:

[0074] Step 1: According to the coating process requirements, spray water-based base paint AR-3500NH-821M and clear varnish Mac O-1900 on a 70mm*150mm electrophoretic plate in sequence, and then dry in an oven to obtain the automotive coating;

[0075] Among them, the water-based paint coating process requirements and varnish coating process requirements are the same as those in Example 1;

[0076] Step 2: Use a 0.4mm thick utility knife to cut the car coating in the middle area of ​​the electrophoretic plate sprayed with the car coating. It is required to cut out 4 unconnected cut areas. Each cut area is required to be a rectangular area with a length of 10mm and a width of 2mm. All water-based paint and varnish should be scraped off in the cut area to expose the electrophoretic coating film to obtain the test sample. Be careful to clean the car coating debris in the cut area. See Figure 1 ;

[0077] Step 3: Use a Mitsubishi drawing pencil, model "UNI" F, certified and issued by the Japan Paint Inspection Association. Use a pencil sharpener to remove the wood covering the pencil lead, exposing the pencil lead. Then use sandpaper (grit size 400) to polish the tip of the pencil lead to a flat cylindrical tip approximately 3 mm thick, thus obtaining a test pencil.

[0078] Step 4: See Figure 2 and Figure 3, use the cylindrical pencil lead of the test pencil to hold the pencil under a load of 15N and press it downward at a 45° angle on the cut line of any cut area (either the long side or the short side). Push the pencil from the cut area to the non-cut area containing the automotive coating at a speed of 3mm / s in a direction perpendicular to the cut line until the cylindrical pencil lead breaks or the exposed cylindrical pencil lead is completely worn away, and the automotive coating in the non-cut area is damaged under the pushing force of the test pencil. Record the length of the cut in the non-cut area;

[0079] Step 5: Use a ruler to measure the scratch length. When the scratch length of three or more of the four scratch areas is ≤5 mm, the composite coating is judged to be scratch-resistant and resistant to scratches and is not prone to paint film damage during assembly. The results are shown in Table 2.

[0080] Table 2 Test results of composite coating scratch resistance and scratch resistance

[0081]

[0082] The above experimental results show that after the composite coating was tested using the testing method of the present invention, the scratch lengths in three of the four scratch areas exceeded 5 mm. This indicates that the composite coating of this color is not resistant to scratches and bumps. Subsequent tracking data indicates that during the two years of automobile assembly operations at the customer's site, a total of five complaints were received regarding damage to the paint film due to bumps.

[0083] Example 3

[0084] Using the scratch and mar resistance testing method for automotive coatings described in this application, the water-based paint AR-2100NH-820P coating and the ColorPro H-3000NH-820P coating were tested to determine the scratch and mar resistance of the water-based paint AR-2100NH-820P coating and the ColorPro H-3000NH-820P coating.

[0085] The specific steps include the following:

[0086] Step 1: According to the coating process requirements, spray water-based paint AR-2100NH-820P and ColorPro H-3000NH-820P on two 70mm*150mm electrophoretic plates respectively, and then dry them in an oven to obtain two automotive coatings;

[0087] The water-based paint coating process requirements are the same as those in Example 1;

[0088] Step 2: Use a 0.4mm thick utility knife to cut the car coating in the middle area of ​​the electrophoretic plate sprayed with the car coating. It is required to cut out 4 unconnected cut areas. Each cut area is required to be a rectangular area with a length of 10mm and a width of 2mm. All water-based paint should be scraped off in the cut area to expose the electrophoretic coating film to obtain the test sample. Be careful to clean the car coating debris in the cut area. Figure 1 ;

[0089] Step 3: Use a Mitsubishi drawing pencil, model "UNI" F, certified and issued by the Japan Paint Inspection Association. Use a pencil sharpener to remove the wood covering the pencil lead, exposing the pencil lead. Then use sandpaper (grit size 400) to polish the tip of the pencil lead to a flat cylindrical tip approximately 3 mm thick, thus obtaining a test pencil.

[0090] Step 4: See Figure 2 and Figure 3 , use the cylindrical pencil lead of the test pencil to hold the pencil under a load of 15N and press it downward at a 45° angle on the cut line of any cut area (either the long side or the short side). Push the pencil from the cut area to the non-cut area containing the automotive coating at a speed of 3mm / s in a direction perpendicular to the cut line until the cylindrical pencil lead breaks or the exposed cylindrical pencil lead is completely worn away, and the automotive coating in the non-cut area is damaged under the pushing force of the test pencil. Record the length of the cut in the non-cut area;

[0091] Step 5: Use a ruler to measure the scratch length. When the scratch length of three or more of the four scratch areas is ≤5 mm, the coating is judged to be scratch-resistant and not susceptible to damage during assembly. The results are shown in Table 3.

[0092] Table 3 Coating scratch resistance test results

[0093]

[0094] The above experimental results show that after the AR-2100NH-820P coating was tested using the testing method of the present invention, the scratch lengths in all four scratch areas were within 5 mm, indicating that the coating of this color is scratch-resistant and resistant to scratches. In contrast, the scratch lengths in all four scratch areas of the ColorPro H-3000NH-820P exceeded 5 mm, indicating that the coating of this color is not scratch-resistant.

[0095] Subsequent tracking data shows that during the nearly five years of ColorPro H-3000NH-820P assembly operations, there were more than 10 complaints each year regarding paint film damage caused by bumps and scratches. However, after the customer switched the color to AR-2100NH-820P, there were no complaints about paint film damage for nearly a year.

[0096] Example 4

[0097] Using the scratch and mar resistance testing method for automotive coatings described in this application, a composite coating consisting of a solvent-based paint SP M-95NH-912P and its matching clearcoat Mac O-330 was tested to determine the scratch and mar resistance of the composite coating consisting of the solvent-based paint + clearcoat.

[0098] The specific steps include the following:

[0099] Step 1: According to the coating process requirements, spray the oil-based paint SP M-95NH-912P and its matching clear coat Mac O-330 on a 70mm*150mm electrophoretic plate, and then dry it in an oven to obtain the automotive coating.

[0100] Among them, the coating process requirements of oil-based color paint and varnish coating process requirements are the same as those in Example 1;

[0101] Step 2: Use a 0.4mm thick utility knife to cut the car coating in the middle area of ​​the electrophoretic plate sprayed with the car coating. It is required to cut out 4 unconnected cut areas. Each cut area is required to be a rectangular area with a length of 10mm and a width of 2mm. All oil-based paint and varnish should be scraped off in the cut area to expose the electrophoretic coating film to obtain the test sample. Be careful to clean the car coating debris in the cut area. See Figure 1 ;

[0102] Step 3: Use a Mitsubishi drawing pencil, model "UNI" F, certified and issued by the Japan Paint Inspection Association. Use a pencil sharpener to remove the wood covering the pencil lead, exposing the pencil lead. Then use sandpaper (grit size 400) to polish the tip of the pencil lead to a flat cylindrical tip approximately 3 mm thick, thus obtaining a test pencil.

[0103] Step 4: See Figure 2 and Figure 3, use the cylindrical pencil lead of the test pencil to hold the pencil under a load of 15N and press it downward at a 45° angle on the cut line of any cut area (either the long side or the short side). Push the pencil from the cut area to the non-cut area containing the automotive coating at a speed of 3mm / s in a direction perpendicular to the cut line until the cylindrical pencil lead breaks or the exposed cylindrical pencil lead is completely worn away, and the automotive coating in the non-cut area is damaged under the pushing force of the test pencil. Record the length of the cut in the non-cut area;

[0104] Step 5: Use a ruler to measure the scratch length. When the scratch length of three or more of the four scratch areas is ≤5 mm, the composite coating is judged to be scratch-resistant and resistant to scratches, and the paint film is not easily damaged during assembly. The results are shown in Table 1.

[0105] Table 4 Test results of composite coating scratch resistance and scratch resistance

[0106]

[0107] The above experimental results show that after the composite coating is tested by the testing method of the present invention, the scratch lengths in the four scratch areas are all greater than 5 mm, which means that the coating of this color is not resistant to scratches or dings.

[0108] Based on the above findings, this color was found to have poor scratch resistance during development, so improvements were made to the color, primarily by increasing the crosslinking density of the coating. The scratch and mar resistance was then tested again using the test method of the present invention, as shown in Table 5. Currently, six months after its launch, no complaints of paint film damage have been received.

[0109] Table 5 Scratch and scratch resistance test results of the adjusted composite coating

[0110]

[0111] The coating solutions provided in the above embodiments are typical cases that once met the relevant testing requirements of GB / T6739, GB / T9286, GB / T1720, GB / T1732, etc., but may still have problems with scratch resistance and mar resistance. In order to respond to customer complaints and eliminate the problems existing in the coatings, technicians further developed a test method that can evaluate the scratch resistance and mar resistance of automotive coatings. After the implementation of this test method, the number of complaints received by the final assembly workshop due to the paint film quality of the paint shop has dropped significantly. The statistical data is summarized in Table 6.

[0112] Table 6 Complaints about paint film quality in the final assembly workshop

[0113]

[0114] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for detecting the scratch resistance and scratch resistance of automobile coatings, characterized in that: The steps include: 1) Preparing a test pencil: Obtain a pencil with a flat cylindrical pencil tip as a test pencil, wherein the exposed length of the cylindrical pencil lead at the pencil tip is 2-4 mm; 2) Preparing a test panel: According to the coating process requirements, spray each coating layer onto an electrophoretic plate to obtain an automotive coating. Use a cutter to create n unconnected cut areas on the electrophoretic plate, where n is an integer greater than or equal to 4. Each cut area must be a rectangular area of ​​the same size, scraped off the automotive coating layer to expose the electrophoretic coating layer, to obtain a test panel. 3) Press the cylindrical lead of the test pencil downward on the score line of any score area at a 44-46° angle under a load of 14-16 N. Push the pencil perpendicular to the score line from the score area toward the non-score area containing the automotive coating at a speed of 2-4 mm / s until the cylindrical lead breaks or the exposed cylindrical lead is completely worn away. Record the length of the score in the non-score area. 4) Repeat step 3) to test other scribing areas and record the scribing lengths.

2. The detection method according to claim 1, wherein When the scratch length of the scratched area accounting for more than 75% of the total scratched area is ≤5 mm, the automotive coating is judged to be scratch-resistant and scratch-resistant.

3. The detection method according to claim 1, wherein The exposed length of the cylindrical pencil lead is 3 mm.

4. The detection method according to claim 1, wherein The pencil is selected from Mitsubishi drawing pencils, model "UNI" F.

5. The detection method according to claim 1, wherein The automobile coating is selected from one or more of a mid-coat layer, a color paint layer, and a clear coat layer.

6. The detection method according to claim 1, characterized in that The length of the cut area is 8-12 mm, and the width is 1-3 mm.

7. The detection method according to claim 1, characterized in that The n is 4.

8. The detection method according to claim 1, wherein In step 3), the cylindrical pencil lead of the test pencil is pressed down on the scoring line of any scoring area at an angle of 45° under a load of 15N.

9. The detection method according to claim 1, wherein The rowing speed is 3 mm / s.

10. The detection method according to claim 1, characterized in that The test pencil is specifically obtained according to the following steps: Use a pencil sharpener to remove the wood covering the pencil lead, then use sandpaper to polish the tip of the pencil lead to obtain a flat cylindrical pencil tip, and finally obtain a cylindrical pencil lead of 2-4 mm to obtain a test pencil; Wherein, the particle number of the sandpaper is above 400.

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