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How to prevent corrosion when welding galvanized steel pipes

Views: 33     Author: Site Editor     Publish Time: 2023-10-17      Origin: Site

Anti-corrosion of galvanized steel pipe welding: after surface treatment, thermal spray zinc.

If galvanizing is not possible on site, you can follow on-site anti-corrosion methods: apply epoxy zinc-rich primer, epoxy mica iron intermediate paint, and polyurethane topcoat. The thickness refers to relevant standards.


Galvanized steel pipe process characteristics


1. Optimization of sulfate galvanizing

The advantages of sulfate galvanizing are that the current efficiency is as high as 100% and the deposition rate is fast, which is unmatched by other galvanizing processes. Because the crystallization of the coating is not fine enough, the dispersion ability and deep plating ability are poor, so it is only suitable for plating pipes and wires with simple geometric shapes. The sulfate electroplating zinc-iron alloy process optimizes the traditional sulfate galvanizing process. Only the main salt zinc sulfate is retained, and the remaining components are discarded.

An appropriate amount of iron salt is added to the new process formula to form a zinc-iron alloy coating from the original single metal coating. The reorganization of the process not only brings forward the advantages of high current efficiency and fast deposition rate of the original process, but also greatly improves the dispersion ability and deep plating ability. In the past, complex parts could not be plated, but now both simple and complex parts can be plated, and the protective performance is also 3 to 5 times higher than single metal.

Production practice has proven that when used for continuous electroplating of wires and pipes, the coating grains are finer and brighter than the original ones, and the deposition rate is fast. The coating thickness reaches the requirement within 2 to 3 minutes.


2. Conversion of sulfate galvanizing

Sulfate electroplating of zinc-iron alloy only retains zinc sulfate, the main salt of sulfate zinc plating. The remaining components such as aluminum sulfate, alum (potassium aluminum sulfate), etc. can be added to the plating bath during treatment to generate insoluble hydroxide precipitation. Remove; for organic additives, add powdered activated carbon to remove them by adsorption.

Tests have shown that aluminum sulfate and potassium aluminum sulfate are difficult to completely remove at one time and have an impact on the brightness of the coating, but it is not serious and can be taken out and consumed. At this time, the brightness of the coating can be restored after the solution is processed and can be processed according to the new process. The ingredient content needs to be added to complete the conversion.


3. Fast deposition rate and excellent protective performance

The current efficiency of the sulfate electroplating zinc-iron alloy process is as high as 100%. The deposition rate is unparalleled by any galvanizing process. The running speed of the fine tube is 8-12 m/min, and the average coating thickness is 2m/min. This is difficult for continuous galvanizing. reached.

The coating is bright, delicate and pleasing to the eye. Tested according to the national standard GB/T10125 "Artificial Atmosphere Test-Salt Spray Test" method, at 72 hours, the coating was intact and unchanged; at 96 hours, a small amount of white rust appeared on the surface of the coating.


4. Unique clean production

The galvanized steel pipe adopts the sulfate electroplating zinc-iron alloy process, which means that the production line troughs are directly perforated without any solution being carried out or overflowing. Each step of the production process is composed of a circulation system.

The solutions in each tank, namely acid and alkali solution, electroplating solution, light extraction and passivation solution, etc., are only recycled and do not leak or discharge outside the system. The production line only has 5 cleaning tanks, which are recycled and discharged regularly, especially for passivation. A production process that produces no waste water without post-cleaning.


5. Particularity of electroplating equipment

The electroplating of galvanized steel pipes and copper wires are all continuous electroplating, but the plating equipment is different. The plating tank is designed with the slender strip shape of the iron wire. The tank body is long, wide but shallow. During electroplating, the iron wires pass through the holes and spread out on the liquid surface in a straight line, keeping the distance between them. However, galvanized pipe is different from iron wire in that it has its own unique features and the tank equipment is more complicated.

The tank body is composed of upper and lower parts. The upper part is the plating tank and the lower part is the solution circulation storage tank, forming a trapezoid-like tank body that is narrow at the top and wide at the bottom. There is a channel for galvanized steel pipe electroplating operation in the plating tank. There are two through holes at the bottom of the tank that communicate with the lower storage tank, and form a plating solution recycling system with the submersible pump.

Therefore, galvanized steel pipes are the same as iron wire electroplating, and the plated parts are dynamic. However, unlike iron wire electroplating, the plating solution for electroplated galvanized steel pipes is also dynamic.


Hunan Great Steel Pipe Co.,Ltd
Hunan Great Steel Pipe Co.,Ltd is a world-class production and service provider of submerged arc straight seam welded pipe as the first subsidiary of Shinestar Group. Hunan Great Steel Pipe Co.,Ltd pays more attention to in the pipeline engineering research areas as a pioneer of China Petroleum Pipeline & Gas Pipeline Science Research Institute.

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