Determination Standard And Reason Of Hot Dip Galvanizing

Attached the amount

Corrosion resistance is mainly determined by the thickness of the galvanized layer, so measuring thickness is often the basis of the main judgment of galvanized quality, galvanized layer by the composition of the steel surface, organization, structure, and different reactions, and the Angle of zinc solution in and out, speed also has a great impact. Therefore, a completely uniform coating thickness is not actually possible. So the measurement of adhesion must not be determined by a single point (part), must be measured by its unit area (square meters) average adhesion zinc weight (g) is meaningful. There are many methods to measure the amount of adhesion, such as the destructive section metallographic observation method, pickling method, non-destructive film thickness meter method, electrochemical method, import and export weight difference estimation method, etc. Commonly used for film thickness method and pickling method.

A film thickness gauge is the most common and convenient method to measure the thickness of the zinc layer by magnetic field induction. The basic condition is that the steel surface must be smooth and complete, so as to obtain more accurate figures. Therefore, in the steel corner or rough, angular steel parts or castings, are unlikely to be an accurate number. Ordinary iron with the original iron angelica zero base material still can get quite accurate numbers, castings are absolutely not accurate.

The pickling method is the most accurate method for formal inspection reports, but it is necessary to pay attention to the fair selection of upper and lower parts when sectioning, so as to obtain accurate figures. But it also has disadvantages, such as time-consuming, complex steel areas are not easy to obtain, and too large parts can not be the whole pickling. Therefore, it is sufficient to make full use of the film thickness meter to control the on-site process and to use the pickling method to do the final test.

homogeneity

Hot dip galvanized steel is the easiest to rust parts, the zinc layer is still the thinnest place, so it is necessary to measure whether the thinnest parts meet the standard.

The homogeneity of the test method generally uses a copper sulfate test, but this method is composed of a zinc layer and an alloy layer of zinc layer skin film test is very problematic. This is due to the different dissolution rates of the zinc layer and alloy layer in the copper sulfate test solution, and the alloy layer is also different due to the difference in zinc/iron ratio. Therefore, it is not very reasonable to judge uniformity by the repeated times of certain impregnation times.

Therefore, in recent European and American specifications and JIS, there is a tendency to abolish this test method, to replace the uniformity by distribution, mainly by visual or tactile sensation, only when necessary with a film thickness meter to check the distribution state. And complex shape of small components because the area measurement is not easy, it is not easy to get the average thickness of the film, sometimes have to use the copper sulfate test method to do reference, but must not be copper sulfate test to replace the purpose of the determination of attachment.

Solid sex

The so-called firmness is galvanized layer and steel tightness, the main requirements of galvanized components in finishing, transportation, storage, and use shall not be stripped of nature, the general inspection method has a hammer, squeezing method, coil attached method, etc.

The hammering method is to hammer the test piece and check the state of the coating skin film surface. The test piece is fixed so that because of the height and level of the hammer support platform, the hammer is centered on the support platform, so that the vertical position of the handle falls naturally, and the 4mm interval parallel strike 5 points, to observe whether the skin film is stripped to judge. However, within 10mm from the Angle or end, this test shall not be carried out, and the same place shall not be struck more than two times. This method is the most common, suitable for zinc, aluminum, and other skin films solid test. Other such as the extrusion method, and coil method are rarely used, so do not mention them.

Ordinary people often have a wrong idea, often in order to facilitate the measurement of firmness, take two galvanized steel, and knock each other to observe the corner spalling situation to judge. If there are just a few thicker zinc particles at the corners. In the operation is not handled well, then a hard knock and thick zinc particles will peel off. Therefore, this method cannot be used to judge the bonding between normal galvanized skin film and iron base.

Adhesion, uniformity, and firmness, that is, the general specification of the definition of hot dip galvanized quality inspection items. It is also the standard of formal inspection reports in general. Relevant specifications.