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Hot Dip Galvanizing of Galvanized Square Tube

Date:2018-01-04    keywords:galvanized square tube
1. Attached amount
Corrosion resistance is mainly determined by the thickness of galvanized layer, so the measured thickness is often the main basis for determining the quality of galvanized, galvanized square tube by the surface composition, organization, structure and have different reactions, the other into and out of zinc solution angle, speed also has a great impact. Therefore, it is virtually impossible to predict the thickness of a completely uniform coating. Therefore, the measurement of the amount of adhesion can not be a single point (part) to determine, it is necessary to measure the unit area (m2) attached to the average zinc weight (g) makes sense. There are many ways to measure the amount of adhesion, such as destructive slicing metallography, pickling method, non-destructive film thickness method, electrochemical method, the weight difference between incoming and outgoing methods and so on. Commonly used for the film thickness method and pickling method.

Thickness gauge (coating thickness gauge) is the most commonly used method of measuring the thickness of a zinc layer using magnetic field induction. The basic condition is that the steel surface must be smooth and complete for accurate figures. Therefore, the corners of the steel or rough, angular steel or castings, are unlikely to be an accurate figure. Ordinary iron pieces with the original iron angelica zero substrate, is still quite accurate figures, the casting is absolutely inaccurate. Pickling method for the official inspection report, the most accurate way, but the slice must pay attention to the fair trade-offs between the upper and lower parts before they can get accurate figures. However, there are also disadvantages such as time-consuming and complex steel area is not easy to obtain, too large pieces can not be the entire pickling. Therefore, full use of film thickness gauge to control the on-site process, and pickling method to do the final test, it has been enough.

2. Homogeneity
Hot-dip galvanized steel most rusty parts, is still the thinnest zinc layer, it is necessary to measure whether the thinnest parts meet the standards. Homogenization test method, the general use of copper sulfate test, but this method for the zinc layer and alloy layer consisting of zinc coating coating test is very problematic. Since the rate of dissolution of the zinc layer and the alloy layer in the copper sulfate test solution is different, the difference in the ratio of zinc / iron in the alloy layer also varies. Therefore, it is not very reasonable to judge the uniformity by the number of repetitions of a certain immersion time.

Therefore, the recent European and American specifications and JIS, there is a tendency to repeal this test method to replace the distribution of uniformity, visual or touch-based, if necessary, check the distribution status with the film thickness gauge. The complex shape of the small components because of the measurement of the area is not easy, not easy to get the average film thickness, and sometimes had to use copper sulfate test for reference, but must not copper sulfate test instead of the determination of the amount of adhesion purposes.

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