C.3 Adhesion test
C.3.1 Coating adhesion test is to use the direct pull-off test method to measure the adhesion between the coating and the object to be coated. This method is suitable for both indoor test and field test
C.3.2 The test shall use pull-off coating adhesion Tester, wet Film Thickness Gauge and microscope Thickness Gauge.
C.3.3 Indoor test should be carried out according to the following steps.
C.3.3.1 Make 10 C30 concrete specimens of 500mx500mx50mm , and cure them for 28d under standard conditions
C.3.3.2 According to the requirements of Article D.1.1 of Appendix D, carry out surface treatment on the non-casting surface of 500mm x 500mm of each test piece .
C.3.3.3 For the 5 wet-surface test pieces that need to be tested for the adhesion of moisture-cured coatings, soak them in clean water after surface treatment, and place the other 5 surface-dry test pieces in the shade indoors.
C.3.3.4 For the coating of the treated non-casting surface of 500mx500mm, according to the requirements of the designed coating system and the instruction manual of the coating product, the bottom layer, middle layer and surface layer shall be painted in sequence. During the coating process, the coating rate of each layer of paint was verified by weighing method, and the wet film thickness of each layer was measured with a wet film gauge. For surface-dry test pieces, first blow off the dust on the painted surface, and for surface-wet test pieces, after picking them up from the water, wipe off the water droplets on the painted surface with a damp cloth, and then paint . The coating method can be brush coating, rolling coating or spray coating. Surface wet test pieces, after each coat , immerse in 3% saline for 4 hours.
C.3.3.5 After the coating is completed, the surface wet test piece is immersed in 3% saline solution picked up after 12 hours, and then submerged again after another 12 hours, so that the curing is repeated for 7 days; while the surface dry test piece is placed in Indoor Nature Conservation 7d
C.3.3.6 Take 3 surface-dry or surface-wet test pieces that have been cured for 7 days, randomly find 3 points on the coating surface of each test piece, each point has an area of about 30mx30m, and use zero-grade fine sandpaper The coating surface of each point is lightly polished and roughened, and degreased with solvents ; at the same time, the aluminum alloy rivet head disc seat of the adhesion Tester is also polished and degreased in the same way. Finally, glue the aluminum disc seat to the prepared coating with adhesive.
C.3, 3.7 After the adhesive has hardened for 24 hours, use the socket cut off the coating around the disc seat so that it is in contact with the coating around the periphery. separated.
C.3.3.8 Put the steel ring support sheet of the adhesion Tester accessories on the disc seat, and then turn the hand wheel of the adhesion Tester counterclockwise, so that the claws of the instrument loosen and embed the aluminum alloy rivet head into the circle. Make the three supporting pillars of the instrument stand on the steel ring support plate, turn the pointer of the instrument to the scale position of "0"; finally, tighten the handwheel clockwise until the coating breaks, and Immediately record the pointer reading. Repeat the test according to this step, pull out each aluminum alloy rivet head disc seat, and record the reading of each pull
C.3.3.9 Use a microscope Thickness Gauge to measure the dry film thickness . Measure at least 30 points for each specimen to calculate the average dry film thickness.
C.3.4 The test of the adhesion of the coating surface sprayed on site shall be carried out 7 days after the coating is applied. Randomly find three measuring points for each 50m2 area for testing, and the specific test method should refer to the relevant provisions of Article C.3.3.
C.3.5 Test results should be evaluated according to the following methods.
C.3.5.1 Immediately after the test, observe the adhesion of the bottom surface of the aluminum alloy rivet head disc seat. If more than 75% of the bottom surface is adhered to objects , the test data is valid.
C.3.5,2 If less than 75% of the bottom surface is covered with coating or concrete , and the tensile force is less than 1.5MPa, the adhesion test can be repeated on the coating surface near the measuring point .
C.3.5.3 Surface-dry or surface-wet specimens respectively take the measured data of 9 test points and calculate arithmetic mean value to represent the adhesive force of the coating.
C.3.6 Test result report should include the following contents
(1) The name of the paint manufacturer;
(2) The names, grades and production batch numbers of various coatings;
(3) The spreading rate of each paint (kg/mn2 or L/m2);
(4) The maximum, minimum and average value of the dry film thickness;
(5) Cohesion of paint coating.
