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Surface treatments of highway guardrail
Aug 08, 2018

1. Galvanizing, also known as hot dip galvanizing and hot dip galvanizing: is an effective metal anticorrosion method, mainly used in metal structures in various industries. The rust-removed steel is immersed in a zinc solution melted at about 500 ° C to adhere the zinc layer to the surface of the steel member, thereby preserving the corrosion. Hot-dip galvanizing process: finished pickling - washing - adding plating solution - drying - hanging plating - cooling - pharmacy - cleaning - grinding - hot galvanizing completed. Hot-dip galvanizing is a result of the older hot-dip method. Since the application of hot-dip galvanizing in France in 1836, it has been a hundred and forty years old. However, the hot-dip galvanizing industry has developed on a large scale with the rapid development of cold-rolled strip in the past three decades. More than 90% of the road corrugated beam guardrails are treated by hot-dip galvanizing process, anti-corrosion and anti-scratch, thick zinc layer, long anti-oxidation time and good anti-corrosion and anti-rust effect.

2. Cold galvanizing is also called electro-galvanizing. It is an electrolytic device that removes oil, pickles, and then puts it into a solution of zinc salt. It is connected to the negative electrode of the electrolysis device, and a zinc plate is placed on the opposite side of the pipe. When the positive electrode of the electrolysis device is turned on, a layer of zinc is deposited on the pipe member by the directional movement of the current from the positive electrode to the negative electrode, and the cold-plated pipe member is processed and then galvanized. Cold-galvanized coatings are mainly anti-corrosion by electrochemical principle. Therefore, it is necessary to ensure sufficient contact between the zinc powder and the steel, and the electrode potential difference is generated, so the surface treatment of the steel is very important. In theory, electrogalvanized can reach or exceed the thickness of the zinc layer of hot-dip galvanizing, but in general, the electro-galvanized layer is generally thin, resulting in anti-corrosion and anti-rust effects are worse than hot-dip galvanizing, and the protection period is also short, scratch-resistant effect. Poor, but relatively low cost, the appearance of hot galvanized bright.

3. Spraying is a surface treatment method that sprays plastic powder onto parts. Spraying is also the electrostatic powder coating that we often talk about. It uses an electrostatic generator to charge the plastic powder, adsorb it on the surface of the iron plate, and then bake it at 180-220 °C to melt and adhere the powder to the metal surface. It is mostly used in indoor cabinets, and the paint film has a flat or matte effect. The spray powder mainly includes acrylic powder, polyester powder and the like. The utility model has the advantages that no thin material is needed, the construction has no pollution to the environment, and is non-toxic to the human body; the appearance quality of the coating is excellent, the adhesion and mechanical strength are strong; the curing time of the spraying construction is short; the corrosion resistance and wear resistance of the coating is much higher; Paint; simple construction, low technical requirements for workers; cost is lower than painting process; some construction occasions have clearly stated that it must be treated by electrostatic spray coating process; there is no common rogue phenomenon in the painting process during electrostatic powder spraying. The wave guardrail mostly uses this technology to treat the surface. Under normal circumstances, there are three ways: 1. Direct injection of steel plate. 2. Cold-galvanized steel plate spray. 3. Steel plate hot-dip galvanized spray.

Dip molding is a plastic coating process in which plastic is applied to a substrate (usually metal), such as: hangers for drying clothes for daily use, handles for pliers, rubber sleeves for scissors, various handrails, and the like. According to whether it needs heating, it can be divided into hot dip plastic and cold dip plastic. According to the raw materials of dip coating, it can be divided into liquid dip coating and powder dip coating. Dip molding is to form a plastic film by uniformly spraying the plastic powder on the metal by heating the metal, or by heating the dip solution into a metal piece to cool it, and then coating the plastic on the metal surface. This process is widely used without the need for molds, low processing costs, easy molding, and various shapes that can be processed. The wave guardrail can be used to treat the surface in this way, but the cost is higher than that of the spray, and the effect is better. Others are mostly used for wire mesh products.

Cold spray zinc

A, cathodic protection

Cold spray zinc is different from general coatings. Its dry film contains more than 96% pure zinc, which provides good cathodic protection for steel. Even in very demanding environments, it can protect steel surfaces for a long time. Anti-corrosion performance is comparable to hot-dip galvanizing, even better than hot-dip galvanizing.

B. Barrier protection

When the cold spray zinc coating is oxidized, a layer of zinc salt is formed on the surface of the coating to provide barrier protection. At the same time, the binder in the cold spray zinc coating also provides an additional barrier protection to slow the oxidation of zinc. Therefore, the anti-corrosion performance of cold spray zinc coating is better than zinc (aluminum), hot-dip galvanizing and other zinc-rich coatings.

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