360° Virtual Tour

Difference between hot-dip galvanizing and cold galvanizing

Table of Contents

KEYWORDS: Hot-dip galvanized pipe, Cold Galvanizing Pipe

Gi pipe can be divided into two kinds: hot-dip galvanized pipe and cold galvanized pipe. While the latter has been banned, the former is still advocated by the government.

Hot-dip galvanized pipe is a kind of pipe with an alloy layer under the chemical reaction of molten metal and iron substrate. Firstly we remove the iron oxide on the steel surface by a process called acid pickle. After pickling, clean it in the mixed aqueous solutions tank with ammonium hydride, zinc hydride Aqueous solution, or ammonium chloride and zinc hydride solution. Then put it into a hot dip plating tank for galvanizing. 

Advantages of Hot-dip Galvanized Pipe

  • l Zinc layer uniform
  • l Zinc layer has strong adhesion
  • l Long service time
  • l Strong corrosion resistance

Because the complex physical and chemical reactions occur between the steel pipe substrate and the molten plating solution to form a corrosion-resistant structure: Zinc – iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe substrate. Therefore, the hot dip galvanized pipe has strong corrosion resistance.

hot dip galvanized pipe

The cold galvanized pipe also be known as an electron-galvanized pipe. Electroplating zinc is work through the electrode reaction. It is an electron chemical method. The zinc ingot is used as an anode, and the zinc atom loses electrons and becomes an ion state to dissolve into the electrolyte. The steel strip is used as a cathode, and the zinc ion is obtained on the steel strip. The electrons are reduced to zinc atoms and deposited onto the surface of the steel strip to form a coating.

It has a very small amount of zinc coating, which is only 10-50mg/m2. Sure it has very bad corrosion resistance. To guarantee product quality, formal manufacturers will not choose the electron-galvanizing process. So only some small factories with outdated equipment do the cold galvanizing, of course, their price is relatively much more cheaper. The Ministry of Construction of China declared officially: Eliminate the outdated cold galvanized pipe in the future, and the cold galvanized pipe is not allowed to use as water or gas pipe. So please beware of low prices when you buy GI pipes. 

Tianjin Tianyingtai Steel Pipe Co., Ltd.(TYT) was established in June 2005 and is professionally engaged in galvanized steel pipe production, ERW steel pipe production, and Scaffolding products production. There are 13 production lines for different steel pipes, 10 processing production lines, and 2 environmentally friendly hot-dipped galvanizing lines. For the hot-dip galvanized steel pipe, we can meet the customer’s personalized requirements, and the zinc amount can be up to 275g.

TYT has established long-term business relationships with clients from all over the world and serves them with processing, warehousing, transportation, distribution, and other technical supporting services. TYT is recognized by the nation, special materials can be customized, and meet different country’s standards requirements (Like ASTM, BS1387, JIS, etc.). such as HG, and YRD, which can guarantee the quality and stability of raw materials. Welcome to contact us for the best price.

More to explore

Ask For A Quick Quote

We will contact you within 1 working day, please pay attention to the email with the suffix “@tytgg.com.cn”