The continuous change in the atmospheric condition has given a steep rise to the corrosive action of nature. In such a calamity humans have created galvanized structure to fight the corrosion against their creation. In spite of the effort to keep their creation safe by process of galvanization success is not always fruitful. The main reason for such failure can be summarized under the poor quality of the galvanized structure. To ensure safety and long lasting galvanized structures it is important a thorough inspection is done on the creation. To achieve such durability in a hot dip galvanized structure an inspecting team must keep in mind the following layouts:

1. Appearance

• Cooling rate: To ensure a durable hot dip galvanized structure, the cooling rate of the product must be above 550F with compression and metallurgical reaction between Iron and Zinc in the solid state. This will ensure uniformity in the colour.

• Steel Processing: The usage of steel in process of fabrication ensures appearance to be both dull and bright, further inter-metallic formation is created due stresses exerted on the steel during the process. This ensures the protection against corrosive agent stays intact making the structure durable.

2. Surface and Condition:

• Bare Spots: This generally takes places due to welding slag and rusting on the surface. To avoid bare spot one must ensure the surface area was properly cleaned before the process of galvanization after pre-treatment. In case of high amount bare spots the entire length of the subject must be stripped and re-galvanized.

• Chain and Wire Marks: During process of transportation chain and wire marks does takes place on the structure. If this results in exposing of the base steel structure, it is important to re-galvanize the area of the structure for better lasting.

• Clogged holes and Threads: The clogged holes are effect of viscous zinc packed in holes below 3mm. This can be avoided by making the holes larger in size, and if 3mm requirement holes clogged by zinc are utility then they must be centrifuge above 500 Fahrenheit. Similarly in case of clogged thread that is the effect of poor drainage, the same principle is to be applied.

3. De-lamination and Peeling: This is usually a coating of Iron and Zinc above the galvanized steel structure that creates a gap between the two layers; it takes places because structures takes a long time to cool down even after brought out from the galvanizing kettle. If peeling the coat meets the required specification of galvanization can be used for further structural demonstration or can be re-galvanized as per requirement. De-lamination usually due to effect of blasting is not the responsibility of the galvanizer.

4. Excess Aluminium in Bath: In case of the process of galvanization Zinc is the major liquid with 98% the rest 2% used is majorly Aluminium – “discretion of galvanizer” as such it creates black mark on the structure. If the spots are visible and small it can be removed. However for huge load the structure must be re-galvanized.

Related: Hot Dip Galvanizing Process | Tanya Galvanizers

These major points during the process of inspection if taken care of, will create a strong galvanized structure for utility purposes.

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The continuous change in the world’s environment has created a steady rise in the process of corrosion against almost every man made structure across the globe. In such a scenario galvanized structures. i.e. “steel and other materials” are the best resolution to fight against corrosion and other corrosive agents.

In most scenarios’ hot dip of galvanized steel structures are done after the process of fabrication. However, in order to allocate a successful hot dip on fabricated steel structure the organizations providing hot dip galvanized services should take into consideration the following major factors:

• In order to properly complete hot dip galvanization organization must avoid narrows gap between the plates that has been laid for the process.
• One should also take a close look that no surfaces are overlapped during the process of hot dip galvanization.
• Taking proper measures to ensure that no overlapping took place in case of angles when placed back to back and even in case of the channels.
• While hot dipping fabricated steel it is important to ensure that the gap between the contacting surface and structure should not be more than 2.4mm. This will allow cleaning solution to enter the structure but the entry of zinc can be completely avoided as zinc is harmful for the steel structure during the process of hot dip galvanization.
• To attain a successful hot dip galvanization process for steel structure it is important that all the welding, are completely sealed and even a opening for a pin is not left over to ensure that no explosion takes places during the process, as trapped air in the structure can give rise to explosion during the process of galvanization.

These important points should always be taken care of while hot dipping a fabricated structure for the process of galvanization. Further, it is suggestible to create sub-assemblies and assemblies for progressive dip because this would allow the structure to be submerge in a single go creating a uniform expansion and contraction.

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These days, there have emerged numerous companies that has been offering top quality hot dip galvanizing services at affordable rates to its clients. One should not compromise on the quality aspect for price. But before trying to avail such services, it will be first necessary to have a clear understanding why galvanizing is considered to be important and required in the first place. Only then can the best services be availed that can prove to be useful and worth the investment made.

About Galvanization

It is considered to be a process to apply protective zinc coating over metals like iron or steel for avoiding premature corrosion and rust. Galvanized steel’s proponents are known to us this method for repairing or to construct steel structures. For instance, they can benefit immensely from lower repair and maintenance costs associated with it due to its special properties.

Need for protection

Without provide adequate protection, it is quite natural for steel to rust quickly because of atmospheric conditions that it faces with time. Again, the degree of rust is likely to depend upon the environment in which the product is present. Rust is regarded to be iron oxide (which is typically red oxide). It is formed with the oxidation and reduction reaction of oxygen and iron, with the presence of air moisture or water.

Although there are present several protective methods to be followed like plastic coating or painting, these methods tend to have their own drawbacks. If damaged, the steel sections are likely to become rusty, thus causing the protective coating to fall away, thereby making such protection types to be unreliable and non-lasting (always require continued maintenance).

Why use hot dip galvanizing of earthing materials?

Hot dip galvanization according to the industry experts is considered to be a wonderful and time proven method to protect steel materials. All material surfaces with this type are dipped into and then coated with molten zinc completely.

Zinc is said to face slow corrosion, thus providing it with extended life as it safeguards the base metal. With zinc being alloyed to iron, there occurs cathodic protection. It does ensure that the smaller steel areas which are exposed due to damaged do not get compromised by rust. The small damaged areas unlike that of organic coatings do not require touch up. Cathodic protection is sure to last for a long time until there is present zinc layer.

Special care is to be taken if the project needs contact between brass or copper and any galvanized material. It is deemed so in humid or moist environment, since there occurs rapid corrosion of zinc. Water running from brass or copper surface may have sufficient dissolved copper within, thus causing corrosion quickly. In case, it applies to the specific situation, then it can be prevented by ensuring flow of water to copper or brass parts from galvanized materials.

Benefits of galvanizing of sub station structures

There are several benefits to be gained through galvanizing, some of which are given below:

• Low long term cost and less maintenance
• Lower cost when compared to stainless
• Longer life expectancy
• Coating performance and longevity reliable
• Protection offered to smaller steel areas exposed due to damage
• Outstanding resistance offered to mechanical damage
• Zero lost time with surface inspection, preparation and painting
• Other types of coating will not offer similar protection

Read more: Sub-Station Structures

Keeping the above benefits in mind, galvanizing is indeed worth the try and effort and a great investment.

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There is a common misconception among many that any type of zinc coating is termed as galvanizing. However, the truth is there are present various processes through which application of zinc coating is possible. HDG or hot dip galvanizing tends to refer to those coatings which are created through immersion of steelwork into zinc in molten form. Two variations are present of HDG process, namely, Pre-galvanizing and Batch Galvanizing.

About Batch Hot Dip Galvanizing

It is a process that is generally used for coating completely fabricated articles. Chemical cleaning is involved of work before immersing in galvanizing bath, specified with EN ISO 1461. The process given below offers full coverage including hollow section internal surfaces without the presence of any uncoated area. Highest corrosion protection level is also offered with the formation of thick coating.

Pregalvanized Steel product

The alternative available will be to take specific product like tubes, wires or sheet and use an automated process to galvanize them.

Pregalvanized Steel Sheet

It is considered to be among the most used of all pregalvanized products, specified with EN 10346. The sheet is uncoiled to be passed through reducing atmosphere before it gets immersed for short time period in galvanizing bath. On withdrawing it from galvanizing bath, there is used a mechanical wiper or air knife for eliminating excess zinc, to produce excellent surface finish. However, the result derived is thin coating varying between 7 and 42 μm depending upon the grade and most products having typical coating thickness of about 20 μm. Once galvanizing is completed, the sheet gets recoiled before the stockholder. It is uncoiled and then cut down for sale to produce uncoated edges.

Pre-galvanized Steel Tubes

Using automated procedure to EN 10240, it is possible to galvanize tubes. Here, immersion times re much shorter and on withdrawal, the tube bore may be blown down by steam to provide adequate surface finish. Coating thickness could be high by about 45-55 μm, even though most of the produced products may have significant thinner coating of about 20 to 30 μm. The tubes can be cut again for resale purpose to size to create uncoated edges.

Pre-galvanized Wire

Wire strands, from practical view point may be coated just using automated process, specified with EN 10244-2. If wiping procedures are used, then there will be shorter immersion times to eliminate excess zinc present and to achieve smooth finish. Again, coating thickness could vary with strand diameter and grade. However, it will be typically around 20 to 30 μm. Although it is not possible to galvanize individual strands to EN-ISO 1461, for such processing mesh can be found suitable for achieving thicker galvanized coating.

Coating comparison

It is essential to understand that both pregalvanized and hot dip galvanizing coatings tend to come with different characteristics. Also, as coating weights get specified for the steel sheet, weights tend to include the sheet’s both sides to ensure that coating life becomes half for equivalent coating weight that is specified within EN 10346.

Choose Tanya Galvanizers for all galvanizing needs

Those interested to get superior quality galvanizing can check out the different types of services offered by ‘Tanya Galvanizers’, the leading company in the domain. They are considered to be cost effective and known not to compromise on the quality aspect. They are completely reliable and can be trusted upon for providing the best and cost effective galvanizing solutions as and when required.

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Some common defects may arise during hot dip galvanizing process. There are several reasons for the causes of such variations and defects to take place.

Galvanized Coatings: Some defects

• Ungalvanized weld areas: The weld areas may have some coating misses which could be due to welding shag being present on the welds. The fabricator is required to remove the welding slag before it is delivered to the galvanizer.

• Mottled or dull gray coatings: Thicker galvanized coatings will be generated by reactive steels which are dull when compared to standard coatings. Such coatings tend to have longer life due to their greater thickness. Moreover, their appearance is steel metallurgy’s function, which is beyond the galvanizer’s control.

• Dark stains present adjacent to welds: Unsealed overlaps may witness preparation chemicals entering them or poor quality welds simply boil from connection during the galvanizing process. This will only cause coating misses and surface contamination during galvanizing. Moreover, anhydrous fluxing salts remaining within the connection are likely to absorb atmospheric moisture, while leaching onto adjacent galvanized surface. Such salt leaching will each eventually the equilibrium. It is necessary to clean wash the affected areas for removing those slight corrosive leachate.

• Inclusions/Dross Pimples: During galvanizing process, dross is generated as zinc iron crystals or in the form in higher melting point when compared to metal in zinc bath. Galvanized coating experiences trapped dross which gives out that gritty or rough appearance to the coating. Dross inclusion presence in coatings will not be found to be detrimental to performance of the coating, since zinc dross resistance is identical, similar to that of galvanized coating.

• Ash staining: During the galvanizing process, there is formation of zinc ash, since it is in zinc that the work gets immersed. The ash that is generated gets skimmed off the molten zinc surface before withdrawal of the work from galvanizing bath. At times, ash can be found to be trapped within the inaccessible areas, while sticking to the external part of the coating, when the bath is exited by the work. A light brown or dull surface stain is left by ash after removal. However, the galvanized coating performance is not affected in any manner.

• White storage staining: Once galvanizing is completed, the items stacked or stored in poorly ventilated, wet conditions will become white bulky zinc hydroxide deposits upon the galvanized coating surface due to atmospheric moisture reaction.

• General surface irregularities and striations: Lines thicker than adjacent galvanized coating and ridges may appear due to varying zinc reaction with steel surface. This is more due to the stress areas upon the steel surface or probably the welds presence or weld metal that is modified metallurgy into parent metal. It is regarded to be a common phenomenon faced with tube and pipe products. However, coating performance is not affected in any manner.

• Bare patches: The uncoated areas of the galvanized work surface are because of inadequate pretreatment in pickling, degreasing, pre-fluxing and poor surface preparation. It is necessary to get the areas repaired by making use of recommend repair procedure or regalvanize the item, if defect is found of sufficient size.

• Puddling, drainage spikes and runs: They are termed to be unavoidable defects in general item hot dip galvanizing process. They are acceptable unless the function assembly of the item is not affected or safety hazard present in service or handling.

The above are stated to be the few of the reasons for defects to appear in galvanizing and amazing solutions to it.

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