The salt spray test () is a test for measuring the corrosion resistance of a sample by exposing it to an environment containing a certain concentration of salt water mist. It is a commonly used corrosion resistance test method in the surface area book.
There are two cases of scratch and no scratch on the salt spray test. The scratched test plate has a specification of 100mm*150mm, and the scratches are generally crossed diagonally, according to the edge of 20mm, not penetrating the diagonal. Scratches should be applied to the substrate through the coating. The 18th sewing machine needle is often used. After the salt spray test for a specified period of time, the change of the coating within a certain range (according to specific regulations) on both sides of the scratched portion is checked. Generally, the coating should have no blistering, falling off, rusting, etc. within 1.0mm on either side of the scratch.
For scratch tools, GB/T1771-2007 standard is said to be hard-pointed, scalpels, razors, knives, and needles are not allowed, but some generally use a utility knife directly, but it is important to note that If you use too much force and cut the tip of the blade, it will affect the test results (this is not recommended). According to the national standard, the compass is the best.
In addition, for scratches, all scratches should be at least 25 mm from each edge and scratch of the test panel. The scratch should be a straight line through the layer to the substrate. A scratch-resistant tool with a hard tip is used to perform the scratch. The scratch should have a parallel or upper widened section and one or two scratches can be drawn. The scratch width of the metal substrate is 0.3mm~1.0mm, unless otherwise specified.
For aluminum sheet substrates, the two scratches should be perpendicular to each other but not intersect. One scratch should be parallel to the rolling direction of the aluminum plate and the other scratch should be perpendicular to the rolling direction of the aluminum plate.
The use of galvanized or galvanized steel sheets results in a difference between the galvanized layer and the metal substrate. The parties should agree on the extent to which the scratches are applied to the coating and the coating.
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