The galvanizing process
Introduction The hot-dip galvanizing is a process in which the components of the steel or iron protected against corrosion by a zinc coating applied by dipping them in the bath of molten zinc. Good results can only be achieved if certain precautions are taken.
1.The design and construction should be suitable for galvanizing.2. For maximum weight to be taken into account the transport and handling requirements during galvanizing.
3.Suitable metals should be used.
4. It should be taken of the situation of the steel surface.
Although Galvanized have learned to be inventive and resourceful in handling difficult shapes and lengths, customers can improve the quality of finished objects making sure the things that those under their control. The customer should be sure that the construction is suitable for galvanizing and there is no paint, weld slag, paint splashes or similar dirt at work. Also steel sent to galvanizing should be possible becomes free from oils or greases..
Galvanizing
The galvanizing is made in a bath of molten zinc, the temperature of which is controlled in most operations between 440 ° C to 460 ° C (Zinc has a melting point at about 419 ° C). In galvanizing operations operate the high temperature process, the zinc temperature may exceed 560 ° C. The metal analysis in the bathroom must comply with the national decisions or the European Standards and is the least 98,5% Zn. The plating process causes the formation of a coating consisting of zinc-iron alloy layer caused by the reaction of zinc to iron in the steel. As the galvanized components are withdrawn from the molten zinc, an additional metal layer of a composition similar to that of the zinc in the bath remains on the surface. The time for which the steel structure is immersed depends, among other factors, the weight and the thickness of the steel parts. In any case, the object to galvanizing remain in the molten zinc up to a temperature similar to that of the bath.
Zinc coatings: life according to the thickness
THICKNESS-COATED ZINC In a given environment, the service life of a zinc coating is directly proportional to its thickness. Although the zinc coating can be applied by various processes, only the hot-dip galvanizing provides a continuous, hard metallurgically bound coating, substantially uniform inner and outer thick. These alloy layers are often covered by a coating of pure zinc and normally produce a shiny silver coating, sometimes with a subtle hint as zinc flower or jewel. Zinc coating thicknesses vary depending on the plating method and it is necessary to watch those who can not afford the lifetime required. It is also important to ensure that all parts of the steel construction are of equal protection, since premature failure of the coating into small parts (eg clamps) can result, important structures require maintenance much earlier than it would be necessary Otherwise.
Requirements for steel surface galvanizing
General
The chemical composition of the steel and the situation which forms the basic material is vital for successful hot dip galvanizing. Influencing the thickness, structure and quality of galvanizing. For best results it is important for the customer to ensure careful preparation of steel components and to ensure that the construction and the design is suitable for galvanizing. A metallurgically clean steel surface is absolutely essential for a satisfactory galvanizing. However, the steel surfaces are usually covered with contaminants / "contamination" or corrosion products as a result of their chemical composition, manufacture, subsequent treatment or the previous year. The "pollution" can be caused by a variety of materials including oils, greases, soaps, dust, old coatings or residues aids / construction aid. The corrosion products include rust and purine / scales caused by oxidation of the steel surface. Preliminary treatment of the galvanized product to be galvanized hot leads to complete removal of corrosion products in the steel which may be removed by cleaning in hydrochloric acid solution surface, but this can not happen in the case of other pollutants. Also, defects at the steel surface such as scratches or striations can cause the zinc coating to react more strongly to the base material, making these regions more apparent after the hot galvanizing.
Hot Galvanization Plus Organic Coating = Double Galvanization System
Definition
Hot-dip galvanizing is the process in which a coating of zinc and zinc-iron alloys metallurgically joined to a steel substrate or immersing the iron in molten zinc. A coating, in the general sense, is a generic term for one or more layers of interconnected polymer coatings on a base.
A dual system is the combination of two independent corrosion protection systems. Ideally, they should also complement one another.
The cost of hot galvanizing.
1. General
Steel is one of the most flexible materials known to man. It can be forged, rolled up, be poured or pressed, welded, cut, pulled, pinched or bent into virtually any shape or size. It can become harder, softer, more brittle and more pliable, stronger or weaker by using alloying elements or heat treatment. It is the most common metal used on our planet and society completely dependent on it. Our homes, shops, factories, cars, ships, trains, trucks, bridges and engines all rely on him. They can be constructed without steel, but with excessive costs. Steel is comparatively inexpensive to manufacture and iron metal from which is extracted is widely available. Nevertheless there is a problem when using steel. If left unprotected in the earth's atmosphere will oxidize and will come back, in fact, iron metal form. The steel needs to be protected from corrosion.2. PAINTING OR hot galvanized?
The painting is often the first choice solution, thinking engineers, the problem of how to protect steel from corrosion. It may seem very attractive on the basis of the initial cost, but there are drawbacks. If painting done on site after the construction, the application of paint and the curing time (drying) will be significantly affected by the weather - it may be necessary to get one weeks between the layers, which increases the manufacturing time. If painting is not done on the spot, before the construction, chances are that the paint will not dry completely before the steel is transferred so there will be losses in the process. This results in substantial waste of time, remedial work that must be done on the spot. A good paint system, well-implemented, under perfect conditions will need to be maintained at frequent intervals between 10 to 20 years. These costs, together with the indirect costs of delay in transmission, will be important.3. Hot dip galvanizing
Another method to protect the steel is galvanized hot. This is a method of protection against corrosion is not in place, but under factory controlled conditions. After the galvanizing process is complete, the coating is "dry" - in other words, it is hard and does not need any more time. Consequently resist damage from handling much better than organic coatings. Also the zinc coating naturally concentrated on the corners and edges giving more protection where it is needed most and where the organic coating is thinner. The galvanizing, unlike painting, protects and inner and outer steel and also because they need maintenance, the hot-dip galvanizing the initial cost and the final cost.4. Long life
The hot dip galvanizing can protect the steelwork for a very long time. Just how much precisely depends on the thickness of the coating and the corrosivity of the environment of the area. The degrees of corrosion for zinc decrease as the atmospheric levels of sulfur dioxide in Europe, falling. Nevertheless, the actual life will be even greater. This relates very favorably with the period of 10 to 20 years before a good paint system need repair.Mechanical design
It is essential to understand the whole design team that will be used galvanizing. The designers will then have to follow the guidance provided by the standards and the information notes issued by the Union galvanizing or their national association. They will give advice about the drainage holes should be made for their size (although consultation with galvanized is often the best way to finalize the drain requirements of a particular project). If instructions are not fully met, it is not destructive to the project because Galvanized will inspect the construction before galvanizing and - after requesting your permission - he will open holes. If the project requires very thin welded structures are rigid in one plane but may have a differential to another, you should consult galvanized at the design stage. Constructions of this type may prove unsuitable for galvanizing the deflection during the release pressure in the galvanizing bath.
Market
Approximately half of the world zinc production, is used to protect steel and iron surfaces. Galvanized steel is vital for building, construction and related industries - particularly for exposed steel structures. For example bridges, pillars, barriers, gates, nails and screws, street furniture and lampposts. The marine industry selects the galvanizing for cost effective protection of iron and steel in fresh and saltwater environments, typically, boat trailers, floating docks and other marine equipment.Benefits
They are highly resistant to corrosion, zinc damaged by atmospheric conditions very slowly giving high and predictable service life.The galvanizing provides good resistance to impact and abrasion, as the coating is molecularly bonded to the steel. Achieved faster construction as is rarely the case of damage to the coating at the construction site because the protection system has been applied before the steel reaches the area.
If the coating suffer accidental damage or puncture or cut, will offer sacrificial protection to small areas of exposed steel. If the area damaged is greater, the sacrificial protection prevents rust from being "run" laterally.
The galvanizing technology is a very low maintenance costs.
Galvanized steel is effective and environmentally acceptable. A large percentage of zinc from recycled sources. The galvanized steel products are themselves easily recyclable with iron and zinc to be recovered at high efficiency levels.
The protection can be accomplished in minutes, with zinc cover both internal and external surfaces - a unique feature that provides internal protection for vital structures such as light poles.
The electroplating may be used in combination with the dye. A plating system and additional paint can be maintained indefinitely and provides an aesthetic appearance option.
The process is very efficient economically when compared to alternative methods of corrosion protection. When galvanized, the initial cost is the final cost.
