For common steel products, in order to improve the corrosion resistance of the surface, the surface is often protected by galvanizing. The current galvanizing process is mainly hot-dip galvanizing, electro-galvanizing, etc., and the quality of galvanizing The quality of the galvanized layer is uneven. The quality of the galvanized layer (that is, the amount of galvanizing per unit area) is commonly used in the industry to measure the quality of the galvanized layer. Below, editor Cheng Cheng will take you to learn about the two different galvanized layer qualities in the national standards. Test Methods.
The national standard "GB/T1839-2008 Test Method for Quality of Galvanized Coating on Steel Products" provides detailed specifications for two different testing methods for quality of galvanized coating. The first method is the chemical dissolution method, which is to dissolve the zinc coating on a known surface area in a test solution with corrosion inhibition effect, weigh the mass of the sample before and after the coating is dissolved, and measure the weight according to the weight. The difference and the sample area are used to calculate the mass of the galvanized layer per unit area.
The test solution preparation method used here is: dissolve 3.5g of chemically pure hexamethylenetetramine (C6H12N4) in 500mL of concentrated hydrochloric acid (ρ=1.19g/mL), and then dilute to 1000mL with distilled or deionized water.
Other things to note:
1. Before the formal test, the oil dirt, dust, water marks, etc. on the surface of the test piece need to be cleaned and then fully dried;
2. The sample needs to be completely immersed in the test solution during immersion, and the end of the dissolution process is judged when the hydrogen gas evolution stops obviously.
Another method of measuring the quality of the galvanized layer is mainly for galvanized steel plates, using X-ray fluorescence measurement; the principle is to use a primary ray generated by a ray source (X-ray tube or radioactive isotope) to irradiate the steel plate covered with metal coating. Under certain conditions, the characteristic fluorescent X-rays (secondary rays) of iron are excited in the steel matrix, and their intensity attenuates to varying degrees when they penetrate metal coatings of different thicknesses. Detect the intensity of secondary rays. When the conditions such as the occurrence of primary rays and the detection of secondary rays are fixed, the intensity of the detected fluorescent X-rays is a function of the thickness of the coating. The coating quality can be obtained by using the quantitative relationship between strength and coating thickness.
GNEE editor's conclusion: The quality of the galvanized layer is related to the corrosion resistance of the galvanized layer, which in turn affects the quality and safety of downstream processed products. It cannot be ignored. Relevant practitioners recommend further understanding more requirements.
