How to make galvanized coating for steel pipe?

How to make galvanized coating for steel pipe？

As it is well acknowledged, galvanized steel pipe is a steel pipe that has been coated with zinc in order to form certain protective layer on the surface of pipe. This coating generally protects the steel from corrosion. Hot dipped galvanized steel pipe is one typical pipe of galvanized pipes in the steel pipe market. As a rule, before the production of galvanized steel pipe, steel materials are placed into a molten bath of zinc. And this process is also called hot dip galvanization. Normally, the two kinds of metals are chemically bound to one another in this processing, and will therefore never separate, resulting in a more resistant and longer lasting version of steel at a mill.

Today, hot dipped galvanized steel pipe has got a large sales share both in the domestic and foreign steel pipe market. Furthermore, due to its wide range of practical applications, galvanized pipe has won the favor of users in the real life. When it comes to galvanized steel pipe, we have to say about its long story of processing technology in history. According to reliable written records, the process of galvanization was first discussed by scientists in the 1770s, nearly 60 years before it was finally introduced in the 1830s. French engineer Stanislaus Tranquille Modeste Sorel took out the first patent for the process in 1937, and began manufacturing it soon after. By the 1850s, Europe was producing galvanized steel out of manufacturing plants located around the continent. The United States followed shortly thereafter, opening its first plant in the 1870s.

In the actual process of the production of galvanized steel pipe, it is necessary for steel pipe manufacturers to have certain professional knowledge of the galvanized coating. In general, factors influencing the thickness and appearance of the galvanized coating include chemical composition of the steel materials, steel surface condition, cold-working of steel prior to galvanizing, bath temperature, bath immersion time, bath withdrawal rate, and steel cooling rate. With reference to the coating thickness, the American Society of Testing and Materials International (ASTM), the Canadian Specification Association (CSA) and the American Association of State Highway and Transportation Officials (AASHTO) specifications establish minimum standards for thickness of galvanized coatings on various categories of items. These minimum standards are routinely exceeded by galvanizers due to the nature of the galvanizing process. On the other hand, the thickness of the zinc layer will also make certain effects on the steel pipe price in the market.

At the end, we have to say that the differences in the luster and color of galvanized coatings do not significantly affect corrosion resistance. The presence or absence of spangle has no effect on coating performance. The well-known spangled appearance found on galvanized products is a crystallization process dependent upon the zinc bath chemistry, the rate of cooling, the method of pickling, the steel chemistry, and the thickness of the coating. Dull gray or patchy matte gray galvanized coatings give a service life equal to bright or spangled coatings since the service life depends on the zinc coating thickness.