When plated parts need to be stacked closely together for storage and transportation, adequate precautions should be taken to prevent white rust. Maintaining a low humidity environment around the plated parts and ensuring adequate ventilation between stacked plated parts can prevent white rust. Minimize it. Specific precautions are described below.

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.

There is a cleaning and cleaning step in the maintenance of internal and external plastic-coated steel pipes, so the cleaning step is also very important. How can it be implemented well? Steel Pipe has some detailed introduction in these aspects. I hope everyone can learn this.

Cleaning of internal and external plastic-coated steel pipes uses solvents and emulsions to clean the surface of the steel to achieve the effect of removing oil, grease, dust, lubricants and similar organic matter. However, it cannot remove rust, oxide scale, welding flux, etc. on the surface of the steel, so it is not suitable for anti-corrosion production. It is only used as an auxiliary method. Rust removal: First, use tools such as wire brushes to polish the surface of the steel to remove loose or lifted oxide scale, rust, welding slag, etc.

The rust removal of hand tools can reach Sa2 level, and the rust removal of power tools can reach Sa3 level. If the surface of the steel is adhered to a strong iron oxide scale, the rust removal effect of the tool will not be ideal and the anchor pattern depth required for anti-corrosion construction will not be reached. Pickling: Chemical and electrolytic methods are generally used for pickling treatment. Only chemical pickling is used for pipeline anti-corrosion, which can remove scale, rust, and old coatings. Sometimes it can be used as a reprocessing after sand blasting and rust removal.

Although chemical cleaning can make the surface reach a certain degree of cleanliness and roughness, its anchor lines are shallow and it is easy to cause contamination. Spray (throw) rust removal: Spray (throw) rust removal uses a high-power motor to drive the spray (throw) blade to rotate at high speed, so that abrasives such as steel sand, steel shots, iron wire segments, minerals, etc. are sprayed internally and externally under the effect of centrifugal force. The surface of the plastic-coated pipe is sprayed (thrown), which not only can completely remove rust, oxides and dirt, but also the internal and external plastic-coated pipes can achieve the required uniform roughness under the action of strong abrasive impact and friction. .

The reason is that when steel is alloyed with chromium, the type of surface oxide is changed to a surface oxide similar to that formed on pure chromium metal. When the addition amount of chromium reaches 10.5%, the atmospheric corrosion resistance of the equal-diameter tee is significantly increased. However, when the chromium content is higher, although the corrosion resistance can still be improved, it is not significant. Moreover, if the surface layer is damaged, the exposed steel surface will repair itself by reacting with the atmosphere, re-forming the oxide, and continuing to provide protection. Steel-plastic pipes must use cathodic maintenance while using anti-corrosion coatings.

After the rust removal treatment on the surface of the steel plate, 95% of the surface area is removed from visible rust, and 5% of the area and original rust spots remain. Use an alloy steel shovel to remove the old paint on the gas tank. This oxide layer is extremely thin, and the natural luster of the surface of the elbow can be seen through it, giving the elbow a unique surface. Use a wire brush to remove internal rust from welds, reinforcement plates and other dead ends.

The adhesion of the coating to the substrate is an important indicator for evaluating the corrosion resistance of the coating. The stronger the adhesion, the better the corrosion resistance, and the more durable the coating. After the surface treatment is completed, apply epoxy coal pitch primer twice to prevent moisture and rust. Use acetone or other volatile cleaning agents to remove oil, tar and other dirt on the surface of the gas tank. Clean the internal and external plastic-coated steel pipes. After cleaning, the surface should be dry, oil-free and dirt-free.

Internal and external plastic-coated steel pipes for water supply have the following characteristics:

First, the inner surface of the internal and external plastic-coated steel pipe has a plastic coating, which can keep the inside of the pipe smooth, reduce the resistance to water flow, and increase the flow of water. In addition, because the water volume is relatively smooth, the water flow needs can be ensured. At the same time, no scaling will occur inside the pipeline during use, and bacteria will not breed, reducing water pollution.

Second, the outer surface of the internal and external plastic-coated steel pipes has a plastic coating, which can increase the adaptability of the plastic-coated steel pipes. The coating on the outer surface of the steel pipe improves the corrosion resistance, strong water resistance, high oxidation resistance, and good solvent resistance. In addition, the environmental impact on plastic-coated steel pipes can be reduced. Because pipes must be buried underground when supplying water, adding an outer coating can effectively extend the service life of the pipes.

What are the procedures for inspecting plastic-coated steel pipes:

The main inspection methods for plastic-coated steel pipes include appearance inspection, appearance inspection, pinhole test, bending test, flattening test, low temperature test, etc. Each inspection method has its own focus.

Appearance inspection is to inspect the appearance quality of coated steel pipes with the naked eye.

Thickness measurement is to measure the coating thickness at any four orthogonal points on the circumference on any two cross-sections.

The pinhole test refers to using an electric spark leak detector to check the steel pipe coating at the specified test voltage, and also to check whether there is any electric spark.

Bending tests are usually performed on a pipe bending machine or mold. It is worth noting that there is no filler in the pipe during the bending test, and the weld is located on the side of the main bending surface.

The flattening test is to place the specimen between two flat plates and gradually compress it on the pressure testing machine until the distance between the two flat plates is four-fifths of the outer diameter of the specimen. During flattening, the weld of the coated steel pipe is perpendicular to the direction of load application. .

The low-temperature experiment refers to placing the test piece in a low-temperature box, staying there for one hour, and then placing it in a normal temperature environment.

In terms of welding technology, straight seam steel pipes can be divided into resistance welded straight seam steel pipes and submerged arc welding straight seam steel pipes. Resistance welded straight seam steel pipes are further divided into high frequency welded straight seam steel pipes, medium frequency welded straight seam steel pipes, and low frequency welded straight seam steel pipes. The submerged arc welded straight seam steel pipe is also called double-sided submerged arc welded straight seam steel pipe or LSAW straight seam steel pipe, where LSAW is (the abbreviation of Longitudinally Submerged Arc Welding is LSAW).

Electric resistance welded straight seam steel pipe is also called ERW straight seam steel pipe. ERW is (Electric Resistance Weldin), and the abbreviation is ERW. High frequency welded straight seam steel pipe is also called ERW straight seam steel pipe. ERW is a general term for resistance welded steel pipes. Straight seam high-frequency resistance welding pipe (Electric Resistance Welding, referred to as ERW) ERW is the first letter of the corresponding English word.

Resistance welded steel pipes are divided into two forms: AC welded steel pipes and DC welded steel pipes. AC welding is divided into low frequency welding, medium frequency welding, super medium frequency welding and high frequency welding according to the frequency. High-frequency welding is mainly used for the production of thin-walled steel pipes or ordinary-walled steel pipes. High-frequency welding is divided into contact welding and induction welding. DC welding is generally used for small diameter steel pipes.

The main steps are as follows:

1. Plate detection: After the steel plates used to manufacture large-diameter submerged arc welded straight seam steel pipes enter the production line, they are first subjected to full-plate ultrasonic inspection;

2. Edge milling: Use an edge milling machine to perform double-sided milling on both edges of the steel plate to achieve the required plate width, plate edge parallelism and bevel shape;

3. Pre-bending edge: Use a pre-bending machine to pre-bend the edge of the board so that the edge of the board has a curvature that meets the requirements;

4. Forming: On the JCO forming machine, first half of the pre-bent steel plate is stamped into a “J” shape through multiple steps, and then the other half of the steel plate is similarly bent into a “C” shape, and finally the opening is formed. “O” shape

5. Pre-welding: join the formed straight seam welded steel pipes and use gas shielded welding (MAG) for continuous welding;

6. Internal welding: Use longitudinal multi-wire submerged arc welding (up to four wires) to weld the inside of the straight seam steel pipe;

7. External welding: tandem multi-wire submerged arc welding is used to weld the outside of the longitudinal submerged arc welded steel pipe;

8. Ultrasonic inspection I: 100% inspection of the internal and external welds of the straight seam welded steel pipe and the base metal on both sides of the weld;

9. X-ray inspection I: 100% X-ray industrial television inspection of internal and external welds, using an image processing system to ensure the sensitivity of flaw detection;

10. Diameter expansion: The entire length of the submerged arc welded straight seam steel pipe is expanded to improve the dimensional accuracy of the steel pipe and improve the distribution of stress within the steel pipe;

11. Hydraulic pressure test: The expanded steel pipes are inspected one by one on a hydraulic pressure testing machine to ensure that the steel pipes meet the test pressure required by the standard. The machine has automatic recording and storage functions;

12. Chamfering: Process the pipe end of the steel pipe that has passed the inspection to achieve the required pipe end bevel size;

13. Ultrasonic inspection II: Conduct ultrasonic inspection one by one again to check for defects that may occur after diameter expansion and hydraulic pressure of the straight seam welded steel pipes;

14. X-ray inspection II: X-ray industrial television inspection and pipe end weld photography on the steel pipe after diameter expansion and hydraulic pressure test;

15. Magnetic particle inspection of pipe ends: This inspection is performed to detect pipe end defects;

16. Anti-corrosion and coating: Qualified steel pipes will be anti-corrosion and coated according to user requirements.

Generally, galvanized pipes do not need to be painted. If they are painted, they are usually painted with silver paint. After the steel pipe is galvanized, the surface is covered with a layer of zinc coating, which isolates the steel pipe from the atmosphere, avoids direct contact and corrosion of the steel pipe by the atmosphere, and is protected. As for the zinc coating on the surface of the steel pipe, due to the relatively strong chemical activity of zinc, a thin and dense layer of zinc carbonate will be formed in the air at room temperature to protect the zinc itself from further oxidation.

Therefore, galvanized pipes, both the surface zinc and the steel pipe itself, are protected from rust and do not need to be painted with anti-rust paint. Only when the galvanized layer is damaged (such as steel pipe welding and the coating at the joint is burned) and the steel pipe is exposed to the air and loses the protection of the galvanized layer, is it necessary to reapply anti-rust paint.

The substrates (anti-rust primers) suitable for galvanized parts include epoxy zinc yellow primer (two-component) and epoxy ester zinc yellow primer. Galvanized parts are non-ferrous metals, and non-ferrous metals have poorer adhesion than black all-metal. Commonly used alkyd iron red primers and epoxy iron red primers on the market are not suitable for use on galvanized parts, otherwise they will easily fall off. It should be pointed out in particular that when alkyd paint is used on galvanized parts, a saponification reaction will occur. Not only will the coating fail, but the original galvanized layer will also be damaged.

Pre-treatment when painting galvanized parts:

1. If possible, you can phosphate the galvanized parts, or spray a thin layer of phosphating primer first.

2. Or sand-sweep the surface of smooth galvanized parts.

3. Wipe the surface of galvanized workpieces and galvanized pipes with solvent (i.e. epoxy zinc yellow primer diluent) to remove the protective layer of crude oil on the workpiece and increase cleanliness.

4. Two-component epoxy zinc yellow primer: Prepare the paint strictly according to the ratio of paint and curing agent, and after curing for 30 minutes, adjust the appropriate construction viscosity before spraying. One-component epoxy ester zinc yellow primer: adjust the appropriate construction viscosity and apply it with the correct construction method.