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.

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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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Galvanizing is termed to be among the most widely utilized methods to safeguard metal from corrosion. This method tends to involve applying zinc in thin coating to thick base metal, to help shield the same from surrounding environment. A good number of lamp posts and street signs can be found to have silver color upon them. This silver is stated to be actually zinc coating.

Why Galvanizing?

Having a metal galvanized provides it with anti-corrosion properties. Without using protective zinc coating, metal would be remain exposed to the different elements and oxidize as well as corrode quickly. As a matter of fact, galvanized steel can prove to be cost effective solution when compared to using materials like aluminum or austenitic stainless steel for preventing corrosion. Hot dip galvanizing services in Vadodara offered by the reputed providers can help the organization to stay ahead in competition.

Know the different galvanizing methods

Several processes are involved for galvanizing metal, which are given below:

• • Hot dip galvanizing: Like the name suggestions, this particular tends to involve the base metal getting dipped into molten zinc pool. Initially, the base metal is to be cleaned chemically, manually or probably both for assuring good quality bond that can be achieved between zinc coating and base metal. After getting cleaned, base metal gets fluxed for eliminating residual oxides present after completion of the cleaning process. base metal gets dipped into heated zinc liquid bath to form metallurgical bond. The benefit derived from this specific method is considered to be economical and can be quickly performed to complex shapes. But final coating is stated to be inconsistent and relative to the other processes of galvanizing.

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• • Electro Galvanizing: This type is said not to make use of molten zinc bath. Rather, the process uses electrical current within an electrolyte solution for transferring the zinc ions into base metal. It involves the electrically reducing zinc ions that are positively charged into zinc metal that gets deposited onto positively charged material. also can be included grain refiners to ensure steel getting smooth zinc coating. This method is applied typically to sheet metal roll. The benefits to be derived from it are precise coating thickness and uniform coating. But the coating may be thinner than zinc coating that is achieved through hot dip galvanizing process, thus resulting in diminished corrosion protection.

Take a look at our blog for Difference Between Hot Dip Galvanizing And Electro-Galvanization

• Pre-galvanizing: It is a method that is found to be quite similar to that of hot dip galvanizing. However, it is at a steel mill that it gets performed, typically on materials, which have already a particular shape. This method involves metal sheet being rolled through a cleaning process, which is similar to hot dip galvanizing procedure. Then, this metal is passed through pool of liquid hot zinc to be recoiled. A major benefit derived from this particular method is that steel sheet in large coils could be galvanized within a short span of time having more uniform coating, unlike that of hot dip galvanizing. However, the cons are that after pre-galvanized metal fabrication takes place, the uncoated, exposed areas become present. It effectively means, when long sheet coil is cut to small sizes, its edges where metal gets cut remains exposed.

Reputed providers like Galvanizers have their certified hot dip galvanizing plant from where they produce different types of galvanized products like cable trays, crash barrier, race ways, earthing strips, earthing materials, sub-station structures and much more.

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For producing building materials of any type does require energy inputs, materials, waste outputs and emission. The key towards sustainable development can be started to lower down the environmental impact upon producing a product. This is achieved through optimizing manufacturing. More objective measures and transparency have been pushed by specifiers, especially those committed towards sustainable development.

The fact is Hot Dip Galvanizing steel does come with several environmental benefits which can help to minimize the overall impact to the environment over the project’s life.

Abundant, Natural Materials

It is from two naturally found elements that are found in abundance like iron ore and zinc that Hot Dip Galvanizing steel is created from. The base metal is iron ore (steel), which is regarded to be the fourth most found element within the Earth’s crust. Hot Dip Galvanizing Coating comprises of about 98% of zinc is considered to be a healthy, natural metal. Zinc of over 5.8 million tons is being cycled naturally through the environment. This is done by rainfall, animal and plant life, as well as another natural phenomenon.

Zinc is also regarded to be essential to life. It is required by humans and even microorganisms to survive. It is equally crucial for growth since it plays a significant role in cell growth, division and wound healing. An important role is also played in the regular functioning like digestion, breathing, cognition and reproduction. Zinc, among all micronutrients, is said to have a very strong effect upon the immune system, thereby helping to fight infection and preventing diseases. It is also used in fertilizers for promoting growth and fortifying crops.

With zinc being found naturally in the environment and cycled throughout, using HDG steel is not likely to introduce any kind of harmful or disruptive elements to the overall eco-system.

Renewable Resources

Steel and zinc being both abundantly naturally found are infinitely recyclable. There is found no loss of chemical or physical properties. It effectively means instead of getting down-cycled into the other types of products or its uses, they can be repeatedly used as steel and zinc, without their integrity getting compromised. Hence, when taking into consideration HDG steel’s life cycle assessment, this can be termed to be a cradle to cradle product. This is because no ‘grave’ exists for steel or zinc.

The other wonderful benefit towards minimising the environmental impact is HDG steel’s 100% recyclability aspect. Its primary components, steel and zinc can be recycled, which is held crucial. Two recyclability measures do exist which will define ultimately the positive contribution made towards the environment, namely, reclamation rate and recycling rate.

• Reclamation rate is said to measure the number of times, the product has been recycled at the end of the useful life.
• Recycling content can be termed to be the volume of product which is produced from the different recycled sources.

The world’s most recycled material is steel, while zinc boasts of having high reclamation rate. Thus, it leads to having a higher recycling rate, since the reclaimed steel and zinc is put back to use once again. When HDG steel is concerned, structural steel’s recycling rate is much better, over 90%. Zinc’s recycling rate is much lower since not much zinc is available for reclamation purpose for creating a recycled product. It is its longevity and durability factor that allows it to be used for decades.

Quality Galvanizing Job work is done by the industry specialists, who can offer the very best, cost effective solutions.

Galvanization is also known as galvanization is considered to be the technique to apply protective zinc coating for the iron or steel, for preventing rusting. Care is to be taken to the fullest extent in several services. This is actually to prevent the pipeline from getting rusted. Otherwise, it can prove to be hazardous to the personnel, may cause malfunction or damage of the instrument, equipment, etc. It is for this particular reason that piping is said to be galvanized.

Some of the commonly used techniques for the purpose of galvanization are stated to be electro-galvanizing and hot dip galvanizing.

Know the differences

If the plan is to order the same, then it is necessary to undertake proper and thorough research of the available materials in the market. This can help the person to be safe with his selection and ensure that the right and most appropriate products are purchased that meets specific needs and requirements of the business. Otherwise, it will be just merely waste of precious time and money. The professionals offering hot dip galvanizing services can help with the selection process.

Below are given some of the basic differences found between electro-galvanization and hot dipped galvanization. Also are provided the benefits offered by both over the other.

• For hot dip galvanization, a very rigid cleaning process is followed, which is generally known as the 7 bath process. Cleaning is done in alkaline solution, pickling, water rinsing, fluxing. In case, of electro-galvanization, there is not followed stringent cleaning method.

• Steel is said to be dipped in molten zinc bath @ 460 degree Celsius to achieve the coat for hot dip galvanization. But in the latter, steel is prepared in cathode in electrolytic cell, thus forming coating using electroplating process.

• Hot dip galvanization produces on steel surface Fe-Zn alloy layer, leaving behind pure zinc coating on outer surface. This alloy is quite hard. Damage is not caused to the coating by the usual abrasion, even though some damage may take place to the pure soft zinc present at the top. Electro galvanization produces Zn layer on surface that is termed to be not continuous with that of steel metallurgically.

• Electro-galvanization has very low life, ranging from several months to some years only. But, hot dip galvanization is known to have very high life averaging between 20 to 50 years.

• Electro-galvanization comes with excellent finish. However, hot dip galvanization has dull, unpleasant finish.

• The coating thickness of hot dip galvanization generally is about 80-100 µm. The coating thickness entirely depends upon the dipping duration. Also, it is affected by the steel’s roughness and composition. For electro-galvanization, coating thickness generally is about 10 to 12 µm. here, the coating thickness is determined upon the electrolyte temperature and current density.

• Hot dip galvanization is said to have normal coat thickness of about 40% much more expensive when compared to electro-galvanizing. The latter has normal coat thickness that is much affordable. But, the cost is said to increase proportionately with higher coating thickness. Hence, it becomes expensive.

• Hot dip galvanization is provided with non-uniform coating, while the other one with uniform coating.

• Hot dip galvanization is suitable for all sizes, while electro-galvanization is suitable exclusively for smaller components.

To know more about the differences between hot dip galvanizing and electro-galvanization, it will be useful to take the help of the reputed companies offering top class hot dip galvanizing services.

There are many who would like to know the type of kind of surface preparation of iron and steel is required before it is delivered at any hot dip galvanizing plant. For protective coatings, few of the specifications include Preparation for hot dip galvanizing before coating inspection and application requirements after and during coating application. Usually, for galvanizing, no special preparation is necessary. Speaking with the reputed hot dip galvanizing services can help the person to make a huge difference to the knowledge gained about the same.

Some Specifications

For the batch hot dip galvanizing, ASTM specifications are arranged differently. A153/A153M and ASTM A123/A123M are some of the commonly utilized specifications for Preparation for hot dip galvanizing. They cover all the inspection need of finished galvanized product.  ASTM A385/A385M, A384/A384M and A143/A143M are said to discuss on fabrication process for steel that are to be hot dip galvanized. They also can address few of the surface preparation recommendations before galvanizing.

The process

It is a simple process that batch hot dip galvanizers tend to involve for preparing iron and steel before galvanizing. Once inspection of steel is completed for ensuring presence of adequate drain holes and vent, it gets dipped into cleaning chemical series. The initial chemical is stated to be a degreasing bath to remove organic contaminant like grease, oil and dirt from metal. Pickling acid is the next type of chemical that is used to eliminate rust (oxides) and mill scale from steel. The final step involved prior to galvanizing is to dip the iron or steel into the flux bath. This is to avoid metal oxidization before entering galvanizing bath, as well as to help galvanizing reaction to develop hot dip galvanized coating.

There are not required any specific parameters for ASTM specifications to clean chemicals that are used within the galvanizing process. General concentration tends to make the chemicals quite effective and every galvanizer does optimize its cleaning chemicals, thus providing them with fabulous results to clean the iron or steel. This way, superior quality galvanized hot dip coating is achieved.

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Few materials which cannot be removed by the cleaning chemicals

Several materials do make use of chemical chemicals before the galvanizing process. They may not be able to remove or face difficulty in removing. List of common materials:

• Anti-splatter and weld splatter
• Weld slag as well as welding flux residues
• Burrs (may include those excessive rough edges derived from flame cutting)
• Heavy or probably extremely adherent type of mill scale
• Asphalt, vinyls, epoxies
• Mill coatings like lacquers or varnishes present on several pipe types
• Sand, other impurities present on castings
• Crayon markers
• Markers and oil based paints
• Thick or heavy grease or wax deposits

Such materials are to be eliminated from the metal before it is delivered to galvanizing plant. There are present some commonly used standards to ensure abrasive blast cleaning, powertool cleaning and hand cleaning. These cleaning methods and the hot dip galvanizing services offered are considered to be effective enough to remove these materials. Usually, abrasive blasting is required on castings for removing sand including other impurities from casting process. Moreover, different types of products could be used on iron or steel that is considered to be compatible with hot dip galvanizing method for reducing the requirements for hand or power tool cleaning or blasting.

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HDG or Hot dip galvanizing is used for safeguarding steel from corrosion in few of the imaginable harshest environments. Still, it is said to offer maintenance-free convenience and longevity, when compared to other types of products. Hot dip galvanizing corrosion resistance tends to vary depending upon its surroundings, but its corrosion rate is about 1/30 of that of bare steel when similar environment is taken into consideration. Actual consumption rate measurement of coating at the initial years of service does offer excellent data to project conservative estimate for rest of the life to that of its first maintenance. The reason is because, it is on the surface that zinc corrosion products are known to build on. In majority of the environments, it is considered to be fairly insoluble and adherent, with the rate of corrosion slowing down with time.

Other factors to consider

Zinc coating is said to come with corrosion resistance that is primarily determined by the coating thickness. However, it varies with environmental conditions and its severity. Hot tip galvanizing is affected in a different manner by each environment, based upon unique series of corrosion variables. The coating’s lifetime predictability is considered to be crucial to plan and budget for necessary maintenance.

Irrespective of being exposed to the atmosphere, or subjected to snow, blazing UV rays, or other types of elements, embedded in soil, submerged in water or concrete or any other type of environment, such type of steel has the capability to withstand various types of corrosive elements. It also can fulfill the desired design life. There are present several sites that does offer good idea about the performance of such type of steel products.

Other things to consider

The truth is that before using hot dip galvanized steel for the project, there is a genuine need to know as to how long it can last. Like with any type of corrosion protection system, there are two common questions pertaining to this product with regards to the costs associated and coating life. A tool has been developed to allow the specifiers to refer quickly a visual guide which approximates the performance of corrosion protection of this steel in different atmospheric conditions.

The estimated time for the initial maintenance of zinc coating against coating thickness in atmospheric applications is depicted through the initial maintenance chart. The coating life estimation in water or soil is not applicable with this chart. It also is known to feature 5 distinctive plotlines that represents climate types along with differing rate of corrosion. With such plotlines as well as knowledge of the coating thickness, trying to estimate the time of the first maintenance of the coating becomes quite simple, similar to that of reading few points on the graph.

With some research and understanding it becomes easier to use the time to initial maintenance chart. When carefully followed, it is likely to give the desired result and show how much long the hot dip galvanized metal can last.

There are many who are not aware of the difference between galvanized and hot dip galvanized metal. Both the terms almost sound the same. For galvanizing, there are present numerous standards. Browsing on the web can help to find some fabulous references and for this, the search needs to be C90 or G60.

People might use the term electrogalvanized for hot dip galvanized metal, even if the article is about electroplated with zinc only. It is from there that some might assume that shortening it to galvanize is legitimate. There are many manufacturers offering zinc electroplated finishes that are less corrosion resistant and thinner than galvanized. But still these are called galvanized!

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What is the difference? – Hot Dip Galvanized Metal and Galvanized Metal 

There does exist a sharp difference between hot dipped galvanized metal and galvanized objects like nails. The new standard that is being used for the pressure treated lumber, according to ACQ states, chemicals which are used in ACQ are likely to corrode the ordinary galvanized fasteners. Hence, special consideration is an absolute must when using ACQ lumber. ACQ is to be used with stainless steel or hot dipped fasteners. Electro-galvanized is a phrase which many may have come across.

Words such as galvanized could be imprecise expect for any specific context. Professionals are likely to state ‘galvanized’ to exactly mean ‘hot dip galvanized’ instead of zinc electroplated (electro galvanized). The latter is a term which is never used by the professionals.

Electro-galvanized

According to many professionals, this term is not required to be used, since, it means the same thing like that of ‘zinc electroplated’. It is regarded to be a term that has been used, accepted and understood universally for ages. It is even stated that probably ‘electro-galvanized’, the term is probably coined by any salesman. This is perhaps to help the company that has been offering less durable and far less expensive zinc electroplating to sail smoothly and pass on the products as superior quality ones.

Some examples

It could be that during construction of a hospital building, the outlet boxes present in the wall need to be sheradized or hot dipped galvanized. The boxes are stated to be zinc plated galvanized manufactured. Is there a need to get the boxes to be hot dipped or simply have the architect convinced they are quite fabulous just the way it seems to be. Since the building is to be a hospital, where there is expected to be used crucial life support equipment, the architect is sure to be concerned about the zinc whiskers. It is regarded to be a stress phenomenon, where the zinc electroplated surfaces can be a definitive subject and the galvanized surfaces have been believed to be quite less.

The hot dipped galvanized metal specifications may appear on the electrical materials due to outdated specifications. Manufacturers are forced by clean air regulations to adopt the new processes, while construction specifications are not noticed to keep up with such requirements.

Moreover, hot dip galvanizing is known to change thread dimensions. However, it is quite common for cutting threads and allows dimensional change.

For more information on hot dipped galvanized metals increase the life of a the metal click here. 

The use of Galvanized Steel is increasing with time in construction sites. Engineers and owners are making good use of perforated galvanized cable trays and other accessories to enhance protection of the expensive wires and cables used extensively in the construction process. The reason for its extensive usage is because, galvanized steel does offer plenty of benefits to those who use it. There is a need to know the different advantages of hot dip galvanizing. Only then should one go ahead with its usage in the construction sites.

Know the major benefits of using Hot dip galvanizing

Galvanizing when used to provide structural steel protection does offer significant measurable benefits, some of which are mentioned below:

• Low initial cost: The truth is that when compared to other commonly used steel protective coatings, the initial cost of galvanizing is much lower. (Labour intensive coating application cost like painting has increased when compared to factory operation related expenses like galvanizing).
• Low long term and maintenance cost: It has been noticed that even in those cases, where galvanizing initial cost is noticed to be higher when compared to alternative coating, it is absolutely much cheaper during the long term process. This is because, it lasts much longer and requires less maintenance. Maintenance generally means more problems and added costs, especially if structures are found in those remote areas and there is involved product disruption or plant shutdown.
• Long life: Life expectancy on typical structure member of galvanized coating can exceed 50 years in majority of rural environments. In severe coastal and urban exposure, it can last about 20-25 years+.
• Tough coating: Galvanized coating is known to have unique metallurgical structure. It offers outstanding resistance towards mechanical damage in service, erection and transport.
• Reliability: It is according to the set standards that galvanizing is performed. Coating life as well as its performance is quite predictable and reliable.
• Auto protection for those damaged areas: Steel can be corroded preferentially by galvanized coatings, thus offering sacrificial or cathodic protection to those smaller steel areas that are exposed due to damage. Unlike that of organic coatings, the smaller damaged regions do not require any touch up.
• Ease of inspection: The Galvanized coating type can be assessed easily by the eye. Even there can be used of ordinary non-destructive thickness testing methods. Galvanizing process can be stated to be a process where coatings may appear continuous and sound and it will be the same.
• Quick erection time: Galvanized steel members can be used immediately upon being received. There is no time lost on site due to surface preparation, inspection and painting. With the completion of assembly structure, it can be used immediately or at later construction stage.
• Full protection: The fact is that every part of the galvanized article stays well protected, which includes those inaccessible areas, sharp corners and recesses. Coating is not applied to the fabrication or structure, after completion could provide similar protection.

The above benefits clearly show why hot dip galvanized items are to be used.

Hot Dip Galvanizing Process – read more

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