Galvanized steel tank weld how to make zinc
Zinc easily forms a dense oxide film, so the zinc-plated steel plate is more corrosion resistant than ordinary steel plates. The galvanized steel drums can be made of raw zinc steel (white iron), or they can be separately galvanized after the bottom cover and the barrel of the drum are formed, and then the steel drums can be synthesized.
The zinc layer on the original zinc steel plate is generally a hot-dip plating process. The zinc layer obtained by hot-dip plating is thicker, and its structural layer is composed of five layers of a steel substrate, a zinc-iron alloy layer, a zinc layer, an oxide film, and an oil film. The steel drum made of hot galvanized steel sheet has good corrosion resistance.
After the bottom cover and the barrel of the drum are formed and galvanized separately, an electrogalvanizing process is used. The zinc layer obtained by this process is a zinc ion adsorbed on the current by the zinc ion, and the formed zinc layer is formed. The structure is relatively loose and thin, and at the same time, since there is no heat penetration, the electrogalvanized sheet lacks a zinc-iron alloy layer, the oxide film formed by it is also thin, and there is no oil film layer protection. Therefore, the corrosion resistance and appearance of electrogalvanized steel drums are not as good as those of steel drums made from raw zinc sheets.
However, when the steel barrel body is made of the original zinc steel plate, the weld site of the barrel body is ground because of the need of welding, and is oxidized after welding, so the galvanized layer here is no longer existent. In order to maintain the galvanized layer of the galvanized steel drum intact to ensure the anti-corrosion performance of the galvanized steel drum, it is necessary to carry out zinc treatment.
Currently, the zinc recovery methods adopted by the steel drum industry can be roughly divided into three types:
The first one is to remove the oxide layer at the weld and hot-melt the tin. However, although tin has relatively stable chemical properties at room temperature and hardly reacts with air, it is prone to form sub-salts in the event of acid, and is liable to form stannate when it encounters alkali. This has a great influence on the overall anti-corrosion performance of galvanized steel drums.
The second is the special zinc coating for galvanized steel drums after grinding the oxide layer at the weld seam. This coating is a two-component coating. It is actually a coating of aluminum paste into X-891 steel drums. One of its components is a curing agent, and the other is an anti-corrosion resin containing aluminum paste.
Metal aluminum can form an oxide film that is denser than zinc, so its corrosion resistance is better than that of zinc. For example, a container made of aluminum has water, sulfide, concentrated nitric acid, any concentration of acetic acid, and all organic acids. Very good corrosion resistance. Therefore, the overall anti-corrosion performance of galvanized steel drums treated with zinc-coated steel galvanized steel barrels has no effect. However, although the coating is dry in about 10 minutes, it takes a long time to completely solidify. Therefore, after the inside and outside of the barrel weld joint is coated with a special zinc coating for the zinc steel barrel, it is better to work on the cover the next day. Coiled so that the coating is fully exposed to oxygen cure. Of course, if the barrel can be baked at a temperature of 180°C for 15 minutes (this temperature has no effect on the galvanized layer), the paint can be completely cured, so that the barrel can be immediately wound with the bottom cover.
Nowadays, many barrel factories will not use special zinc-removing coatings for galvanized steel drums (in fact, transparent X-891 special paints for drums) with aluminum paste, which are more commonly used in the overall coating of electrogalvanized steel drums. Since the zinc layer of the electrogalvanized steel drum is adsorbed by zinc ions under the action of current, the zinc layer structure is not as dense as the oxide film and oil film on the surface of the original zinc (white iron) steel drum, so the appearance and protection against oxidation , Anti-corrosion performance is poor, over time, the appearance of hairiness, pulverization and corrosion. However, after coating a very thin layer of transparent 891 coating on the surface of the galvanized steel drum, not only the overall oxidation-proof and anti-corrosion performance of the galvanized steel drum is greatly enhanced, but also its appearance is bright and gorgeous, and the coating is dried. And soon. Since only a thin layer is required, the unit consumption is very low. Some barrel factories can actually coat more than 20 200-galvanized steel drums with 1 kg of 891 paint.
Some barrel factories use silver powder paint to make up the weld seam. Although the silver powder in silver powder paint is actually aluminum powder, first of all, the content of aluminum powder in silver powder paint is low, and secondly, silver powder paint is mostly prepared by ordinary blended lacquer and aluminum powder. , Its anti-corrosion performance is poor, so it is relatively reluctant to make up the weld.
The third method is the best way to supplement zinc in galvanized steel barrels. It is to use galvanized steel barrels dedicated weld zinc supplementation machine for zinc smelting.
Galvanized steel barrel dedicated welding zinc supplementation consists of sandblasting and zinc spray.
Since the galvanized steel barrel welds are oxidized due to welding, the oxide layer must be first removed to refill the zinc layer. Galvanized steel barrel dedicated weld zinc supplementation machine to remove the oxide layer is carried out by sandblasting.
When the barrel body comes down from the welder, it is lifted by the hoisting machine to the sandblasting box mouth (since the lower part is sanding, so the blasting box is made higher), and the position of the supporting wheel in the blasting box is aligned with the tank mouth. The barrel enters the box and is positioned directly on the supporting wheel. The operator will weld the sandblasting gun mouth and press the control button after positioning. The two sandblasting nozzles opposite to the blasting mouth start sandblasting both inside and outside the steel barrel. At this time, the supporting roller drives the barrel body to move in parallel under the action of the air pump or the motor, so that the whole weld of the barrel body is completed from the beginning to the end along the blasting gun mouth, so that the oxidation on the inside and outside welds of the galvanized steel barrel is The layer is completely removed.
The sandblasting power can be Shi Guojia's air pressure in the sand storage tank, or it can be driven by the negative pressure generated by the compressed air flow. Sand particles are easily affected by the pressure difference during the spraying process, and welds sprayed with damp sand tend to produce rust in the rising temperature caused by the sand particles. Therefore, the galvanized steel tank welding zinc supplementing machine also needs sanding equipment matching. To ensure that the sand used for blasting is dry.
After dust removal, it enters the zinc sprayer, and the action and spray are basically the same. The operator will press the control button after aligning the weld joint with the zinc spray gun, and the two spray nozzles will be opposite to the spray gun at the same time on the galvanized steel drum. The inside and outside of the weld seam begin to spray zinc. The zinc spray gun melts the zinc wire according to the high temperature generated by the combustion of acetylene, and the liquid zinc is sprayed on the barrel through the resulting air pressure. The zinc wire is automatically synchronized with the melting speed. Follow-up.) At the same time, the support wheel drives the barrel to move in parallel. The whole weld of the barrel body is completed from the beginning to the end of the zinc spray gun, so that the entire damaged zinc layer inside and outside the galvanized steel barrel is completely filled.
Because the temperature of zinc replenishing zinc is very high, it is easy to form zinc-iron alloy layer, and the outer surface is also easy to form a dense oxide film. Therefore, the galvanized zinc galvanizing machine is the closest to the galvanized zinc galvanized steel barrel. The structure of the original zinc (white iron) plate.