galvanized square tubes
Galvanized steel pipes are divided into cold-dip galvanized steel pipes and hot-dip galvanized steel pipes. Cold-dip galvanized steel pipes have been banned, while the latter are still recommended by the state for temporary use.
Before galvanizing, the steel pipe needs to be pickled, cleaned, rinsed, dipped in solvent and dried. The welded pipe is hoisted by a crane into the pickling tank for pickling.
The anti-corrosion performance of galvanized steel pipes comes from the fact that their surface has been hot-dip galvanized. This process can give the steel pipe a uniform and highly adherent zinc layer. This layer of zinc is closely combined with the steel pipe matrix, not only providing additional protection, but also covering the steel pipe with a layer of corrosion-resistant armor through chemical reactions. Despite this, it is still possible for it to rust in actual applications. There are many factors behind this.
First of all, the galvanized layer is not a completely seamless defense. It is formed under specific hot-dip process conditions, which include key parameters such as material selection, galvanizing thickness, temperature and time. If these parameters are not properly controlled, the uniformity and adhesion of the zinc layer may be affected, thereby reducing its corrosion resistance.
Secondly, environmental factors play a decisive role in the corrosion resistance of galvanized steel pipes. In a humid environment, the zinc layer reacts with moisture and oxygen in the air to form a basic zinc carbonate film. This chemical reaction process is a natural oxidation process. Although it can protect the substrate to a certain extent, if there are substances such as hydrogen sulfide in the environment, the corrosion resistance of zinc will be significantly reduced. Hydrogen sulfide can react with zinc to form zinc sulfide, which can further corrode the substrate and accelerate the rusting process.
In addition, the electro-galvanizing process is unique compared to traditional hot-dip galvanizing. Galvanized steel strips that are electro-galvanized have a thicker coating, which can more effectively isolate the steel plate from the external environment, reduce the occurrence of oxidation reactions, and thus reduce the probability of rust.
In summary, although the surface of galvanized steel pipes is specially treated to improve corrosion resistance, its rust problem is still closely related to factors such as environmental conditions, process parameters and the performance of the zinc layer. Correctly understanding and applying this knowledge is crucial to preventing or delaying the rust problem of galvanized steel pipes.
Cleaning with clean water is to rinse the inner wall of the steel pipe with clean water, but it cannot completely remove impurities such as calcium and magnesium ion scale and biological slime attached to the inner wall of the steel pipe, and the effect is not obvious.
Cleaning with chemical solution is to add chemical reagents to water, but the chemical components are corrosive to steel pipes and also shorten the life of steel pipes. It is a practice of fishing in a dry pond and is not advisable.
Spiral steel pipe is a spiral seam steel pipe made of strip steel coil as raw material, extruded at room temperature, and welded by automatic double-wire double-sided submerged arc welding process.
In the current market, the working principle of this type of cleaning is basically to use compressed air as the power, and use a launcher to launch a special projectile larger than the inner diameter of the pipe into the steel pipe, so that it moves along the inner wall of the pipe at high speed and fully rubs to achieve the effect of cleaning the inner wall of the pipe. This method has obvious cleaning effect and basically does not harm the pipe. It is the most thorough cleaning method so far.
Generally, galvanized pipes do not need to be painted. If they need to be painted, they are usually painted with silver powder paint.
After the steel pipe is galvanized, a layer of zinc coating is covered on the surface, which separates the steel pipe from the atmosphere, avoids direct contact and corrosion of the atmosphere on the steel pipe, and protects it. The zinc coating on the surface of the steel pipe, due to the strong chemical activity of zinc, will form a thin and dense layer of zinc carbonate in the air at room temperature, protecting the zinc itself from further oxidation.
Therefore, the galvanized pipe, whether it is the surface zinc or the steel pipe itself, is protected and will not rust, and does not need to be painted with anti-rust paint. Only when the galvanized layer is damaged (for example, when the steel pipe is welded and the coating at the joint is burned), the steel pipe is exposed to the air and loses the protection of the galvanized layer, then it is necessary to apply anti-rust paint.
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