Coating detector, I would like to say to you (4) - about the corrosion test coating scratch operation, do you understand?

1, scratch purposeAt present, many relevant international and domestic standards related to corrosion tests are stipulated in the test before the scratch, and then carry out the relevant corrosion test, before the corrosion test will be the main purpose of the coating scratching three points:(1) simulation and study of specific types of damage during exposure;2, scratch patternscratches generally require penetration of the coating to the metal substrate, the use of different scratch tools scratches to produce a representative different shape of the scratch effectThis difference can greatly affect the results of corrosion tests, as scratches on the coating system are intended to allow oxygen and electrolytes to be exposed to metal surfaces that are active in the test environmentThe tools actually used for scratches are determined based on the type of coating and the thickness of the coating, and the scratch method and repeated re-scratches under the same conditions have a significant impact on the corrosion processscratches are common in the shape of X-shaped, T-shaped, or a single line, as shown in Figure 1The length of the scratch should be significantly greater than the expected spread width after the corrosion testFigure 1 The width of the scratch shapescratchon on the paint test board also has an effect on the results of the corrosion testThe narrower the scratch, the stronger the tendency of the exposed metal surface to be passivated due to the accumulation of a small amount of corrosion product solutionIt is therefore extremely important to select a suitable tool so that scratches of the right width can be drawn for corrosion testingthe direction of the scratch has a considerable effect on the results of the corrosion testFor example, in the saline spray test, horizontal scratches will accumulate more salt solution on a model placed at a smaller angle in a vertical directionThe distribution of salt solution on horizontal scratches is also more uniform, while the angular or vertical scratches are prone to gradient distribution, and the solution down along the scratch esmotic gradually increases, the increase of the salt solution will lead to an acceleration of corrosion rate, but on painted steel plates, high concentration salinous solution may inhibit corrosion because the corrosion products it produces are very dense the cross-section of the scratches along the entire length of the scratch should be as uniform as possible Smooth lyceising coating along the direction of the scratch Depending on the scratch tool selected, the cross-sectional shape of the scratch can be "V" or "U", as shown in Figure 2, the shape, depth, and uniformity of the scratch depends on the manual scratch tool and is also associated with the scratch operator Figure 2 penetrates the cross-sectional shape of the coating scratches
3, several standards involving scratches
3.1 Common involving scratch standard sGB/T1771-2007/ISO7253:1996 "Measurement of color paint and varnish neutral salt spray performance" iSO20340:2009 "Color and varnish offshore building sand and paint and related structure studs protective performance and related structure sage protective system" 4-2008 "Standard Test Method for Painted Sample Evaluation in A Corrosive Environment" GB/T30786-2014/ISO17872:2007 "Metal plate coating scratch marking guidelines for color paint and varnishe corrosion test" 3.2 standard description related to scratches
Each edge and scratch of all scratches from the test model should be at least 25mm between each other;" the scratch section is parallel to both sides or the upper widening section, requiring a certain width (0.3mm to 1.0mm)"
; mm, 2mm wide, parallel to short edges, and 25mm from adjacent long edges, short edges", asasd 1654-2008: "If there is no special agreement, the general dash should be crossed all organic coatings on the substrate to the metal substrate, resulting in one or several uniform bright lines without burrs." In addition, it is stipulated that the scratch pattern is V-shaped incision"; ASTMD1654-2008 and GB/T1771-2007/ISO7253:1996 all stipulate that "the degree of marking the cutting of metal plating shall be agreed by the parties concerned"
; 4, scratch tool and auxiliary tools
4.1 scratch tool
tool is mostly tungsten carbide, a few carbon steel, hard texture the scratch tools specified in other commonly used standards: asTMD1654-2008 recommends using the type E
/T30786-2014 in ANSIB94.50, the appendix lists a number of scratch tools
note: no use of tools such as blades, needles, anatomical knives and other scratches 4.2 auxiliary tools a metal ruler, used to draw a specified length of scratches
a microscope, magnifying 25 times magnifying glass, magnification 5 to 10 times, used to observe whether the scratch is uniform and auxiliary removal of scratches when the debris 5, scratch operation steps
the test model fixed to ensure even scratches, to avoid the test plate or tool sliding scratches along the metal ruler with a scratch tool, scratches that penetrate the coating to the substrate, and the scratch movement is continuous and consistent Caution: Do not damage the surrounding coating the coating is cut through to the substrate with a minimum number of times can be viewed with a magnifying 5to 10 times magnifying glass to confirm that the scratches are uniform and that the debris produced when the scratches are removed " paint tester, I would like to say to you (5) - paint in the harmful heavy metal element content of the test, you have a deep understanding? relevant wonderful article (click on the title to read) "serial" paint detector, I would like to say to you (1) - from the experimental auxiliary staff W wipe window sill caused by the feeling "serial" paint testing personnel, I would like to say to you (2) - non-volatile content determination, you did the right thing? "serial" paint detector, I would like to say to you (3) - "fine" to operate, reading has "degree", how can do a good job of coating "fineness" test?