HDG Steel Pipe

Our factory
We are a team with profession, efficiency, enthusiasm, concentration and integrity, our employees have more than 20 years working experience in the related fields.

Our product
Our main products are: Welded steel tube,hot dipped galvanized steel tube,cold rolled steel coil/sheet,hot dipped galvanized steel coil/sheet,ppgi,ppgl and etc.

Production market
Company engaged in import and export of steel and raw materials for construction, which committed to providing competitive price, high quality products and best after-service for america, asia, africa and other countries.

Our serve
From the high production, quality assurance and fast delivery, to the packing, examine cargo and after service, we will check every step and processes to provide you a purchasing business in saving both time and labor.

The essential difference between hot-dip galvanized and cold-dip galvanized pipe
(1) Cold-galvanized pipe is also called electro-galvanized pipe. It is to use electrolysis equipment to put the workpiece into the solution composed of acid salt after degreasing and pickling. And connect the negative pole of the electrolysis equipment, place a zinc plate on the opposite side of the steel pipe and connect it to the positive pole of the electrolysis equipment, turn on the power, use the directional movement of the current from the positive pole to the negative pole, and a layer of zinc will be deposited on the steel pipe.
(2) Hot-dip galvanized pipe is also called hot-dip galvanized pipe, which is a method in which steel hooks are immersed in molten zinc liquid to obtain a metal coating. It is to degrease the steel pipe, pickle it, soak it in medicine, dry it, and then immerse it in the molten zinc liquid for a while, and then take it out.

The principle difference between hot-dip galvanized and cold-dip galvanized pipe
(1) Cold-galvanized pipes use chemical principles to separate zinc alloys into zinc ions, which are attached to the surface of steel. Generally, the zinc layer is thin, and steel is easy to corrode in general environments. Generally, cold-galvanized pipes are used for anti-corrosion of various steel products and structures. The amount of galvanizing of cold-galvanized pipes is very small, only 10-50g per square meter.
(2) Hot-dip galvanized pipe as we all know, the mechanism of zinc's anti-atmospheric corrosion includes mechanical protection and electrochemical protection. Under atmospheric corrosion conditions, there are zno, zn(oh)2ji and basic zinc carbonate protective films on the surface of the zinc layer, which can slow down the corrosion of zinc to a certain extent. This protective film (also known as white rust) is damaged and a new film will form.
When the zinc layer is severely damaged and endangers the iron substrate, zinc will electrochemically protect the substrate. The standard potential of zinc is -0.76v, and the standard potential of iron is -0.44v. When zinc and iron form a micro-battery, zinc is dissolved as an anode, and iron is protected as a cathode.
The formation process of the hot-dip galvanized layer is the process of forming an iron-zinc alloy between the iron substrate and the outer pure zinc layer. The iron-zinc alloy layer is formed on the surface of the workpiece during hot-dip plating, which allows a good combination of iron and pure zinc layer.

The appearance difference between hot-dip galvanized and cold-dip galvanized pipe
(1) In appearance, the hot-dip galvanized pipe looks rough, while the cold-dip galvanized pipe is brighter and smoother.
(2) The application difference between electro-galvanized and hot-dip galvanized bolts: How many years can hot-dip galvanized bolts keep rust-free.

Hdg steel pipe, also known as hot dip galvanized pipe, is a steel pipe that is galvanized for general steel pipe to improve its service performance. Its processing and production principle is to make the molten metal react with the iron substrate to produce an alloy layer, so that the substrate and coating can be combined. How are hdg steel pipe processed? The process flow of hdg steel pipe is divided into the following steps:

1. Alkali washing: Some steel pipes have oil stains on the surface, so alkali washing is required.

2. Pickling: Hydrochloric acid is selected for pickling to remove the oxide skin on the steel pipe surface.

3. Rinsing: Mainly to remove the residual acid and iron salt attached to the steel pipe surface.

4. Dipping aids: The role of flux is to remove all impurities from the steel pipe surface, ensure the clean contact between the steel pipe and the zinc solution, and form a good coating.

5. Drying: Mainly to prevent the steel pipe from being immersed in the zinc pot and blasting.

6. Hot dip galvanizing: The temperature of zinc liquid in the zinc pot shall be strictly controlled at 450+5 ° c, the steel pipe shall be put into the galvanizing furnace and rolled into the three zinc dipping spirals in the galvanizing machine. The three spirals have different phases, making the steel pipe inclined on the spirals. With the rotation of the spirals, the steel pipe moves downward at one side to form an angle of inclination, and then enters the zinc bath, continues to move downward, and automatically falls on the slide rail in the zinc pot; when the steel pipe is lifted to the magnetic mixing surface, it will be attracted and moved to the pulling wheel track.

7. External blowing: The steel pipe passes through the external blowing ring to compress the air and blow away the excess zinc liquid from the steel pipe to obtain a smooth and clean appearance.

8. Pulling out: The amount of zinc can be controlled and the zinc consumption can be reduced by appropriately reducing the pulling out speed.

9. Internal blowing: Remove the excess zinc liquid on the inner surface of the steel pipe to obtain a smooth and clean inner surface. The removed zinc liquid forms zinc powder for recycling.

10. Water cooling: The temperature of the water cooling tank shall be controlled at 80 ℃, and the galvanized pipe shall be cooled.

11. Passivation: The passivation solution is sprayed on the finished pipe of the blow ring to make the pipe surface passivated. After the external blow ring, the excess passivation solution is blown off with compressed air.

12.Inspection: The galvanized steel pipe falls on the inspection bench, after inspection, the missing galvanized pipe is put into the waste basket, and the finished pipe is packed and put into storage.

One. Surface treatment can be used to reduce the occurrence of white rust on the coating. Galvanized pipes and hollow plated parts can be coated with a layer of varnish after galvanizing. Products such as wires, plates and mesh materials can be waxed and oiled. Hot-dip galvanized structural parts can be subjected to chromium-free passivation after water cooling. Deal with. If the plated parts can be transported and installed quickly, no post-processing is required.

In fact, whether hot-dip galvanizing requires surface treatment mainly depends on the shape of the plated parts and possible storage conditions. Plated parts that are tightly stacked or nested have poor protection against white rust, especially when they are stored for more than several weeks. Of course, if the surface of the galvanized structural part is fully exposed, post-processing is generally not required. If the galvanized surface is to be painted within 6 months, an appropriate post-treatment process must be selected to avoid affecting the adhesion between the zinc layer and the paint.

Two. Plated parts should be stored in a covered storage room in a dry, well-ventilated environment.

Three. If the plated parts can only be stored in the open air, the plated parts should be elevated from the ground and separated by narrow spacers to provide free flow of air to all plated parts surfaces. Plated parts should be placed at an angle to facilitate drainage. Plating should not be stored on wet soil or rotting vegetation. Separators are also recommended when shipping, if condensation is likely to occur on the surface of the plated part.

In addition, if the plated parts will cool down when transported over high mountains and then exposed to warmer and moister air at ground level, insulators must be used in this case. Wood containing rosin cannot be used as insulation or packaging because rosin itself is corrosive. It is recommended to use dry, untreated wood such as poplar, locust and fir when transporting and storing plated parts. Small plated parts stored in containers should be dried thoroughly before packaging. When sealing with packaging boxes, it is recommended to add some desiccant.

Four. Do not place covered plated parts where they may be affected by rain, fog, condensation and snow.

Five. When galvanized steel is shipped by sea, they should not be checked as surface cargo, nor should they be placed in the ship’s bilge where they may come into contact with bilge water. Under electrochemical corrosion conditions, seawater intensifies white rust corrosion. At sea, especially in tropical oceans, where humidity is high, it is particularly important to provide a dry environment and good ventilation facilities.