The superiority of hot dip galvanizing

The advantages of hot-dip galvanizing
The following features make the zinc coating is the best: adequate thickness, uniformity and adhesion, sufficient for normal manipulation with products.
In practice, you can get very fitting cover, when the thickness doesn’t exceed 80-100 microns. The greater the thickness increases, the less coverage in condition to stand the power effect, especially the pulse type. The appearance and thickness of the zinc coating may be different in either case, depending on the chemical composition of the steel.
We had an opportunity to consider how some elements such as carbon, silicon and phosphorus, increase the reactivity degree of steel, even when they present in very small quantities and produce a thick coating with a grayish color. However, these types of coverage save all anti-corrosive performance in the same way as the most aesthetic bright and shiny surface.

Reliability

During the hot-dip galvanized steel is completely immersed in molten zinc and all of its surfaces stay covered including inner parts, corners, cracks and fine detail. Coating even gets thicker at the corners and edges, in contrast to what happens when covered with brush or by immersion in other types of protection.
It is possible to protect whole structure including inner surface, pipes and hollow items or if its necessary only to the outer part.

Simplicity of process

Hot-dip galvanizing process is simple, easily controlled, tested and automated in some cases.
The result is a correct and constant. The thickness can be determined in accordance with quite precise specifications. Therefore, covering lifetime can be determined in accordance with the function which the product assigns for and by the conditions of the environment in which it will serve.

The lower cost
The low initial cost and durability make galvanizing the most versatile and cost-effective system for protecting steel in the long term (20 years and more). There are many advantages that connected with a longevity of protection and ability not to interfere with the work of care.

Reduced access to structures
Hot-dip galvanizing reduces a problem of access to remote areas, inaccessible terrain and structures having very close parts to each other. Also when there are security restrictions, for example, in the case of transmission poles.

Less stops for maintenance
In certain circumstances, service may be difficult or impossible because of location or because of the difficulty or inability to stop the plant with continuing operations. Also it can be impossible in the case of petrochemical equipment, power transmission poles or structures in remote areas. In such cases, expenses related to the periods of more than 25 years clearly show the benefits of hot dip galvanizing compared to other forms of protection.

Ease of use
The use of hot-dip galvanizing is light and the whole protective system can be realized in a short period. Alternative systems (especially painting) need in use of labor force. Hot dip galvanizing is highly mechanized and allows to realize the treatment of large quantities of steel and iron products. It also allows to realize an automatic control in a real time.
After galvanizing steel is ready for use. After the installation it doesn’t require a surface preparation, dyeing, finishing touches and inspections. Thus, the construction time is much reduced.

Execution time
When galvanizing runtime is very short, and it allows you to save money.
Because of the need to perform work on HDG production with following costs for transport. It is often chosen production that a place located near the way between the manufacturer and the place of installation of the product.

Ease of control

In the hot-dip galvanizing the checking of coating thickness is simple and immediate, because the question is about visual inspections or audits realzed by means of magnetic or electromagnetic gauge.

System reliability and constant results

The nature of the process is such that when the coating is homogeneous and stable you can be sure that it has precisely these characteristics.
The suitability of the coatings obtained by hot-dip galvanizing is self-contolled. Indeed, if the metal protective surface is not prepared well, the reaction between steel and molten zinc doesn’t occur immediately and the defect is detected.
Typical costs of zinc for control are less than half cost for system with multi-layer paint coating.

Ease of repair

If the repair after hot-dip galvanizing needed, a local treatment realized at the place (thermal spray, application of zinc alloy or zinc paint) I will be simple.

Strength

With increasing of Vickers’ strength for  galvanic protection added a mechanical type protection against of possible damage during handling, storage, transportation and use of products.

Other advantages

Usually, pure (external) zinc soften the impact. An internal alloy is stronger than steel and gives strength.
In addition:
- Hot galvanizing can be applied to all steel products.

- The process of galvanizing produces a surface on which the waste is difficult to accumulate.

- It is possible the connection of all contact surfaces save. This is impossible with most of paints.

- Bonding with bolts is easy to dismount - this is a great advantage for moving bridges with lattice coupling beams or ladder structures.

- When mounted structure is immersed in a zinc bath we get more durable product.  Car manufacturers immerse fully assembled car body in the zinc bath and than affirm that the strength increases by 50%.

- A modest investment in steel galvanizing extends the life of the structure and can economize on other products. For example, in reinforced cement with zinc rod the coating thickness may be less with the subsequent benefit of weight reduction.

- Zinc coating provides a good thermal conductivity between different parts of structure - the basic quality (for example, for blade exchanger).

- Electrical conductivity is also good.

- Especially good corrosion resistance exists in an alkaline environment.
Summing up: the protection of a galvanized iron can be evaluated in three ways because hot-dip galvanizing protects steel in three ways.
1) Protection with the "barrier effect" against the attacks of environment, which allows you protection to subside very slowly and  in foreseeable manner.
2) Cathode protection with primary corrosion coating in a favor of small areas can be  subjected to different influences: holes, cutting, scratching, etc., which are sealed with zinc corrosion products.
3) "Sacrificial" protection that prevents a spread of rust on surface that wider under the edges of possible initial damages.
Indeed, when accidental damage is detected the electrochemical properties of zinc-iron alloy not to make damage as a hotbed of corrosion. Protection of zinc in small scratches – is just one and self-sanitized. While in other forms of protection even small scratches are the beginning of rapid deterioration.

Development in the future

- The forecast tendency of costs in the future goes to strengthen of hot-dip galvanizing role. It suffices to compare the cost of painting with the cost of galvanizing in the past 30 years. And, above all, labor costs which effect greater on the cost of painting and thermal spray than the cost of hot dip galvanizing. This is especially true when you consider to get really good color quality. It is necessary to prepare the base surface of the sand-blasting method (not a hasty cleaning with brushes) and all these are very expensive operations.
Probably these trends will continue into the future.
- A lot of zinc and possibly in the future it will be less expensive than competing materials.
- Historically the cost of zinc (which is one third of the cost of hot-dip galvanizing) did not follow the inflation.
- Control of the environment and taxes on energy will stimulate to a significant increase of materials’ cost for industry. But it is possible that the galvanized steel will experience fewer restrictions because of environmental reasons and because of lower growth in value compared with the systems of dyeing and also water-based.
- Clean environment will allow to galvanized iron exist for a long time, while the ultraviolet rays (that easily penetrate into a clean atmosphere) are a factor of deterioration of paint. It is t possible that the tendency to use galvanized steel structures in construction and in many other areas will develop.
The last argument makes more probable the assumption of a great prevalence of hot-dip galvanizing in the future. The reason is in the fact that some countries have lagged behind in the use of population per unit of galvanized steel and also relatively a modest average value, estimated at about 8% of the product that is suitable for galvanizing.

The appearance of galvanized products, influence of environment

Galvanized products at the end of process has a silver shiny surface. Then it covered with a blue-gray patina consisting of insoluble basic zinc carbonate having a matte appearance: the natural color of zinc. Eventually atmospheric influence gradually turns it into a soluble zinc hydroxide. The duration of this transformation depends on longevity of protection.
Possible remains of zinc hydroxide trapped in the earth have good effect that intensifies fertility.
From the optical point of view, the impact on the environment is acceptable because the color of zinc is well blended with the color of the sky, sea and nature in general.

Some difficulties in the using of hot-dip galvanizing

a) Hot-dip galvanizing can be done only on certain plants.
b) Most of the difficulty of welding compared to bare steel.
c) Limiting the size of items for galvanizing. Depend on the size of galvanizing baths.
d) Risks of deformation or breakage of items. It is possible if they are not designed in accordance with the requirements of hot-dip galvanizing.
Finally it is almost possible to get rid of the reasons of deficiencies.
The real strength of hot-dip galvanizing is in the fact that any subsequent intervention care is almost superfluous. And it has economic benefits that can easy to imagine.
In general, hot-dip galvanizing (HDG) is the maximum evolution of protective systems with respect to steel products. HDG has objective benefits of economic nature. HDG shows a professionalism of that people who use it and let them to get privileged position compared with the those who don’t use HDG.