Paint knowledge: what is the standard of paint adhesion

Core tip: there are several methods to determine the adhesion of paint: circle method, grid method, pull out method, twist open method, and row x method in American ASTM, among which the easiest one is circle method to determine the adhesion of paint film, and the most commonly used one on site is grid method (1) The adhesion tester used for the determination of adhesion by the method of circle drawing is evaluated according to the integrity of the paint film within the scratch range, expressed by grade It is fixed on the tester according to the prepared tinplate In order to make sure that the paint film is completely scratched, weight shall be added as appropriate Shake the handle evenly at 80-100r / min in clockwise direction to roll the scratches, Paint knowledge how about Akzo Nobel Powder Coating Recommended introduction: powder coating is a kind of coating with different form from general coating, which is in powder form It is a new type of coating, because of its own advantages and more and more known by people Let's introduce Akzo Nobel Powder coating Akzo Nobel Powder coating is a cost-effective coating solution, which can be applied to different kinds of products After the treatment of static electricity and fire baking, a tough and durable coating surface will be formed, with the least impact on the environment Since the introduction of this technology, powder coating has been able to continue to maintain the Paint Home News: there are several methods to determine the adhesion of paint: circle method, grid method, pull method, twist method and the X-cut method in American ASTM, among which the most convenient method is circle method to determine the adhesion of paint film, and the most commonly used method on site is grid method (1) the adhesion tester used for the determination of adhesion by the method of circle drawing is evaluated according to the integrity of the paint film within the scratch range, expressed by grade It is fixed on the tester according to the prepared tinplate In order to make sure that the paint film is completely scratched, weight shall be added as appropriate Shake the handle evenly at 80-100r / min in a clockwise direction, and scratch with a round rolling line The standard round length is 7.5cm Take out the sample and grade it The following points should be paid attention to in the experiment: (a) the needle of the tester must be sharp, otherwise it is impossible to distinguish grade 1 and grade 2 Before measuring, you should first touch with your finger to see if it is sharp, or change it after measuring several test plates (b) try to carve several circles first, and the scratch should just scratch through the paint film If the base plate is not exposed, add weight as appropriate; but do not add too much to avoid increasing resistance and wearing the needle (c) at the time of rating, Grade 7 (innermost layer) or grade 1 (outermost layer) can be used for rating Check the integrity of the paint film of each part in sequence If there are more than 705 grids in a certain part, it is considered that the part is intact, otherwise it is considered as damaged For example, if the film of Part 1 is intact and the adhesion is the best, it is determined as grade 1; if the film of Part 1 is damaged and Part 2 is intact, the adhesion is determined as grade 2 According to analogy, level 7 adhesion is the worst Generally, it is required that the adhesion of primer should reach level 1, and that of topcoat can be around Level 2 (2) the standards for the determination of adhesion by the cross cut method are ASTM d3359, iso-2409 and gb9286-98 The test method is basically the same as the description, but the order of the description of the adhesion level is just the opposite Astmd3359 is a 5b-ob level from good to bad, while iso-2409 is a 0-5 level from good to bad The experimental tool is a grid tester It is a multi blade cutter with six cutting surfaces The cutter clearance is 1mm, 2mm and 3mm (the cutter head can be replaced) After the sample is coated on the sample plate and dried for 16 hours, pull 3-4cm in parallel with a scriber, and there are six cuts, which should cut through the paint film to the substrate; then use the same method to be vertical with the former, and the same six cuts; in this way, many small squares are formed For soft substrates, each diagonal is formed along the grid with a soft bristle brush, and the grade can be evaluated by scanning forward and backward slightly several times; For the hard substrate, clean it first, then stick on the tape (3m tape is generally used), and ensure that the tape is in full contact with the experimental area You can rub it back and forth with your fingers to make it in good contact, and then pull it out quickly Use the visual or magnifying glass to compare and grade with the standard and the attached drawings The standard description of its classification is: level description 0 the cutting edge is completely smooth, no one grid falls off, 1 there is a little coating falling off at the intersection, and the affected area cannot be significantly greater than 5% 2 there is coating falling off at the intersection of the incision or along the edge of the incision, and the affected area is 5% - 15% 3 The cross cutting area affected by partial or total peeling off along the cutting edge is 15% - 35% and the whole strip along the edge is off Some grids are partially or completely off The degree of peeling off of 35% - 65% of the affected area is more than grade 4 When the cross cutting method is used to measure the adhesion, the film with the thickness of 250 μ M can be measured at most According to the coating thickness, different grid spacing can be selected, generally, the coating is less than 60 μ m, the hard substrate spacing is 1mm, and the soft substrate spacing is 2mm; the coating thickness is 60-120 μ m, and the soft and hard substrate spacing is 2mm; the coating thickness is greater than 120 μ m, and the soft and hard substrate spacing is 3mm According to iso12944, the adhesion needs to reach level 1 to be qualified; in GB, the adhesion needs to reach level 1-2 to be qualified The difference between the delimitation method and the delimitation method is that the area of the parts formed by the intersection of the delimitation is increasing, and the rating is to examine the location of the undamaged area, while each delimitation area of the delimitation method is fixed, and the rate of the damaged area is used for the rating (3) the adhesion measured by the pull apart method refers to the vertical and uniform tensile force applied on the cemented surface of the sample at the specified speed to measure the force required for the adhesion failure between the coating or between the coating and the substrate, expressed in MPa This method can not only test the adhesion degree between the coating and the substrate, but also the adhesion between the coatings It can also check whether the compatibility of the coating is reasonable, and comprehensively evaluate the overall adhesion effect of the coating The relevant standards of pull off test are iso4624-2004 (latest version), astmd-4514, gb5210, etc Elcometer adhesion tester is commonly used to measure pull off method in foreign countries This instrument is small and can be used for field test However, in some cases, the accuracy of the test results is affected by the instability of manual operation of the elcometer-106 manual pull tester, which is no longer used in some countries The Elcometer test is to stick an aluminum test pull head on the coating, pull the pull head off with a calibrated mechanical tensile tester, and read the pull force of the aluminum head off the scale Generally, three failure types may be found in the pull off test on the metal matrix: (a) adhesion failure, that is, the adhesive layer breaks from the coating or the test pull head or its own internal pull off after tensile force, which is considered as the failure of the adhesive The adhesion between the coating and the substrate or between the coating and the coating exceeds some values (b) adhesion failure, i.e separation of the coating from the substrate under tension, which is the adhesion of the coating to the substrate (c) cohesive failure, i.e the coating itself is broken, which is taken as the value of interlayer adhesion, and the adhesion between the coating and the substrate exceeds this value For each kind of coating, there is a specified pull off method to determine the value, which is generally required to be greater than 2MPa, and the epoxy two-component coating is required to be greater than 4MPa It should be noted that there is a certain gap between the pull off adhesion data measured by Elcometer tester and that measured by national standard tensile tester According to the experience of many experiments, the data of Elcometer tester multiplied by 3-3.5 times is close to the value measured by tensile machine Therefore, the test data of each test method can only be compared in the same kind, with a certain degree of accuracy When filling in the test report, it is also necessary to indicate the test instruments and methods used For the requirements of adhesion, the adhesion of coating system (dry film thickness greater than 250 μ m) in ISO12944-6 is required to be tested according to the pull off method of ISO4624, at least 5Mpa For the old coating, the reference value is 2MPa If it is lower than 2MPa, the old coating shall be removed Home of coatings focuses on coatings, paint coatings, coating technology, news and information of fire retardant coatings, coatings, coating technology, decoration knowledge and decoration renderings of fire retardant coatings,