Pre Galvanized Steel Pipe Factory? The 68 Latest Answer

What is galvanized steel pipe?

Galvanized steel pipe is the carbon steel pipe coated with a protective layer of zinc. The zinc layer served as a sacrificial layer, it rusts from the carbon steel underneath. Galvanized steel pipe includes two types: hot-dip galvanized steel pipe and cold-galvanized steel pipe. The galvanized layer strengthens the anti-corrosion properties of steel pipes.

Why use zinc as a top coat?

Why use zinc? Because zinc element is more active than steel element. On the other hand, zinc oxide of galvanized steel pipe surface is compact, it can stop oxidation (corrosion). On the other hand, when electrochemical corrosion has occurred, the first type of damaged metal is zinc rather than steel. The zinc layer effect stops the corrosion rate and extends the service life of steel pipes.

Galvanized steel pipe application

Galvanized steel pipe used primarily to transmit coal gas and steam. It was used as a water pipe, but after a few years there was a lot of rust in the pipe and the water turned yellow in color because it carried iron oxide. The water not only contaminated dishes or other sanitary ware, but also carried bacteria generated on the inner surface that was not smooth. As a result of corrosion, the water contains too many heavy metal elements and is harmful to health. Because of this, developed countries have banned its use as a hookah since the 1960s.

Galvanized tubular steel types

Galvanized steel pipe includes two types:

1. Hot-dip galvanized steel tube.

2. Cold galvanized pipe, also called electro galvanized pipe.

Galvanized Steel Pipe Sizes and Specifications

Nominal diameter (inches): 1/2~4

Nominal Wall Thickness (mm): 2.0~4.5

Proof Pressure Index: Diameter: 10.2~168.3mm 3MPa

Diameter: 177.8~323.9mm 5MPa

Introduction of hot-dip galvanized steel pipes

Hot-dip galvanized steel pipe is made in the manufacturing process using rust-removed steel pipe, which is immersed in a zinc liquid at a temperature of 500℃, and to produce a zinc layer applied on the steel surface to achieve the purpose of anti-corrosion.

Hot-dip galvanizing is a kind of effective anti-corrosion treatment used on kinds of structural steel products. It has been more than 180 years since hot-dip galvanizing was first used in industry in France in 1836. However, following the development of cold-rolled steel, it has developed greatly in recent decades. With the high voltage transmission, transportation and communication, the protection products require higher standards, and the demand for hot-dip galvanizing is also increasing.

Processing of hot-dip galvanizing:

Finish Pickling – Washing – Electroplating – Drying – Hang Electroplating – Cooling – Medication – Cleaning – Grinding – Hot Dip Galvanizing.

Zinc thickness for hot-dip galvanized steel pipe

The zinc layer thickness of hot-dip galvanized steel pipe is 35μm, and the thickest is up to 650μm. Instead, the cold zinc layer thickness is only 5-15μm. The zinc layer has the effect of air anti-corrosion and electrical chemical protection.

The theory of the zinc layer effect of hot-dip galvanized steel pipes on corrosion protection

In hot-dip galvanizing, a film of a zinc-steel alloy layer is first formed, with a layer of pure zinc on top. When the air corrodes the zinc layer, it forms a layer of ZnO, Zn(OH)2 and a basic zinc carbonate protective film. Which have the effect of anti-air corrosion. When this film has been destroyed, a new one will form. If the zinc layer is severely destroyed, zinc will start electrical chemical protection. Zinc as the first dissolved element. Obviously, hot-dip galvanized steel has better anti-corrosion performance than cold-dip galvanized pipe.

How Long Lifespan of Hot Dip Galvanized Steel Pipe?

Galvanized steel pipes have a long service life. But under different conditions, the usage time is different. Generally 13 years in heavy industrial area, 50 years for marine environment, 104 years in suburbs, 30 years in city. In fact, galvanizing has played a role in preventing rust, no other rust treatment is required.

Hot-dip galvanizing process, especially suitable for kinds of strong acid, alkali mist and other severe corrosive conditions. This type of fasteners is widely used outside of the steel tower post.

Introduction of cold galvanized steel pipes

Cold Galvanized Steel Pipe uses an electroplated zinc layer on steel pipe. The zinc layer is usually 20 to 30 μm thick.

Manufacturing process of cold galvanized steel pipe:

Degreasing – electroplating – passivating – drying – packaging

Zinc thickness for cold galvanized steel pipe

The zinc thickness of cold galvanized steel pipe is 5-15 μm, the layer is dense and there are no inclusions with organic matter.

Cold galvanizing technology is no longer recommended for tubular products.

For the sake of thinner zinc layer, countries in the world have gradually banned cold galvanized steel pipe as water pipe and coal gas pipe. But due to the cold galvanizing processing, the surface has a smooth appearance and is always used to manufacture small parts that require precise plating. Such as screws, machinery, electronics, precision instruments, chemicals, light industry, transportation, weapons, aerospace, nuclear energy, etc., has great importance in the national economy.

Unistrut is the adult version of our youth’s erector set. Our Erector Sets gave us an endless number of possibilities to design, create and build. The Unistrut system works the same way, offering a wide variety of mounting options, hole patterns, tread configurations, materials and finishes needed for project success. Material selection is an important step in the specification process and we offer a wide range of application specific choices based on material alone. When we combine a basic material choice (e.g. carbon steel) with our available finish options, the total number of permutations available increases exponentially. This post takes a closer look at Unistrut’s finish options and provides guidance on choosing the right duct and fittings for your project.

Simple (PL)

Plain Unistrut means the trough retains the oiled finish applied to the raw steel during the rolling process. Fittings with a PL finish will retain the original oiled finish of the bar stock. If your application requires welding, Plain Unistrut is often a good choice because extensive surface preparation is not required.

Perma Green III (GR)

Unistrut’s perma-Green III finish provides excellent resistance to chalking, cracking and fading. The Perma Green surface is also less susceptible to common acidic atmospheres, solvents and alkalis. Unlike many competitive paint-based coatings, Perma-Green III contains no toxic metals. The Perma Green finish offers more protection than Plain Unistrut Channel, but if you’re looking for added protection against corrosive elements, consider some of the options below.

Pre-Galvanized Zinc (PG)

Pre-galvanized Unistrut is zinc plated during a hot dip process for added corrosion resistance. Steel strip from a coil is fed through a continuous zinc coater which cleans, fluxes and coats the steel with molten zinc. After cooling, the steel is coiled up again. The PG zinc coating conforms to a G90 thickness designation per ASTM A653. Zinc thickness is 0.75 MIL or 0.45 oz./sq. ft. area. This proven coating is suitable for indoor and outdoor applications. For more corrosive environments, our Unistrut hot-dip galvanized profiles and fittings are the next step in finish protection.

Hot Dip Galvanized Unistrut (HG) ASTM A123 or A153

In hot-dip galvanizing, the finished part is immersed in a bath of molten zinc. This process produces full zinc coverage and a thicker coating than pre-galvanized or plated zinc. Zinc coating is typically 2.6 MIL or 1.5 oz./sq. ft. area. For many years, the hot-dip galvanized finish was Unistrut’s most corrosion-resistant finish. If you are considering using Unistrut with a zinc coating, it is important to remember the correlation between zinc coating life and thickness, as shown below.

Unistrut Defender™ (DF)

Electroplating is a broad term generally used to describe any metal that has been coated with zinc. However, there are different methods to apply a zinc coating. In terms of hot dip galvanizing, which involves dipping the galvanized h-channel steel posts in molten zinc, there are two distinct variations known as batch galvanizing and pre-galvanizing.

Batch hot dip galvanizing

Batch galvanized steel posts are made by dipping steel posts into molten zinc after they have already been made. Before galvanizing, the pins must be thoroughly cleaned in a careful process called surface preparation.

This cleaning process involves 3 steps – degreasing, pickling and fluxing the pins. Degreasing removes contaminants, pickling removes traces of iron oxide, and fluxing removes remaining oxides. If the post is not properly prepared it will not be electroplated effectively as zinc will not react where contamination is present.

After the surface preparation is complete, the steel post is immersed in a zinc bath that coats the entire post.

Advantages of Hot Dip Galvanized H Channel Steel Posts

Hot-dip galvanized steel posts have a number of advantages. Since the steel posts are completely galvanized, they have increased protection against corrosion. This means they are impervious to harsh weather conditions. Also, the zinc coating on galvanized steel posts is often thicker at the edges and welds, adding durability to the post’s weakest points.

Pre-galvanized steel

Pre-galvanized metals are made by galvanizing the steel in sheet format. This is done through an automated process. The sheet is unrolled and then enters a reducing atmosphere before being immersed in a bath of molten zinc. Upon removal from the bath, a mechanical wiper removes excess zinc.

After galvanizing, the sheet metal is cut to size and wound up again. The steel sheet has a uniform, uniform thickness. For this reason, pre-galvanized steel is more aesthetically pleasing than hot-dip galvanized steel.

After the sheet metal is galvanized, it is processed into various products such as pipes and open ducts. Pre-galvanized steel is generally not suitable for fabrication into galvanized h-channel steel posts as it would not provide the same strength or reinforcement as hot-dip galvanized steel posts. Because materials galvanized after production have twice the layer thickness.

Factors that weaken Zinc Plated H Channel Steel Posts

Placing H Channel Zinc Plated Steel Posts in direct contact with copper or brass in a humid environment will cause the zinc coating to quickly corrode due to a chemical reaction known as bimetallic corrosion. To avoid this, the steel posts should be kept away from copper or brass.

Here at RW Steel we stock a full line of Zinc Plated H Channel Steel Posts to suit every project and budget. Contact us here if you have any questions or click here for a free and non-binding offer.

Galvanized steel is corrosive to all metals except lead, tin, zinc and aluminum. Although not indefinitely durable, galvanized steel is the most corrosion-resistant metal. However, it should be noted that the application of a protective coating such as paint to galvanized steel reduces the problems caused by corrosion of the protective zinc coating.

Galvanized steel has been used for nearly 2,000 years for its unparalleled ability to last and resist rust. Hot-dip galvanized steel and electro-galvanized steel are manufactured using different processes, and their galvanized coatings corrode completely differently. Learn more about these galvanizing processes (here) and how zinc corrosion varies between them (here). Yes, the resistance of galvanized steel to rust corrosion largely depends on the type and thickness of the protective zinc electroplating coating, but the type of corrosive environment is also a critical factor. Factors that cause galvanized steel to rust and corrode:

How long does galvanized steel last?

So how long does it take for a handy new galvanized steel bucket to rust and corrode into a useless pile of metal? It needs a lot of time. A galvanized steel bucket (made by any process) can last practically forever if used carefully and kept dry and out of the rain. But for these galvanized buckets and tubs, which are destined to become garden planters, landscape decorations, pet feeders and farm water buckets, corrosion is inevitable. Galvanized steel intended for prolonged outdoor use should be hot-dip galvanized steel; which typically lasts about 70 years in many different environments.

Table 1 below predicts how long galvanized steel will last based on a 30 month 2004 corrosion study of environmental factors such as wet, humid and airborne pollutants.

Table 1. Prediction of consumption of zinc layer on galvanized steel Galvanized steel in damp or wet environment 10 years at 100% relative humidity 34 years at below 60% relative humidity. 211 years

Source: Journal of Materials in Civil Engineering 2004 (11)

The corrosion resistance of zinc coatings is primarily determined by the type and thickness of the coating, but will vary with the severity of the environmental conditions they are exposed to (as in the table above). The corrosion resistance of the hot-dip galvanized zinc coating mainly depends on a protective film (patina) that forms on its surface.

Read more background:

types of galvanizing; Compare the properties of electroplating methods.

Will rust galvanized zinc; Learn how a hot-dip galvanized zinc coating corrodes and forms a layer of patina that can protect the underlying zinc metal for over 75 years. Zinc corrosion products from hot-dip galvanizing build up (form a patina) and insoluble in metal in many environments. Therefore, the corrosion rate of hot-dip galvanized steel can slow down over time.

The nature of zinc galvanizing and how this process controls the way the galvanized steel corrodes must first be understood. However, the environments, elements, and conditions that a particular type of galvanized steel is exposed to actually determine how long it will last from corrosion.

A 1926 study of the corrosion of galvanized steel in industrial, rural, and marine regions found:

In any location, the life of the zinc coating is directly proportional to its thickness.

Corrosion occurred fastest at the highly industrial sites and least at the rural and drier sites (9).

The handy chart below (from the American Galvanizers Association) shows how long galvanized steel will last before corroded areas should be serviced to prevent further deterioration. Would you like to learn how to finish galvanized steel? Click here. In other words, this chart shows how long it takes for galvanized steel to rust in different environments.

The thicker the zinc coating, the longer galvanized steel will last without corrosion. The thickness of the zinc is shown along the horizontal axis (8). As noted in the table below and in the 1926 study, the corrosion rate for each site is essentially constant over time (9).

Chart 1: Time to first sign of corrosion in different environments

The following environments are listed from most corrosive to least corrosive:

Industrial Environments:

Most cities and urban areas as examples of urban environments.

Generally the most aggressive corrosive environment.

Sulphide and phosphate air pollution from point sources such as car exhaust causes the depletion of galvanized zinc coatings.

Tropical marine environments

Regions where the temperature, if any, falls below freezing.

Humidity is high and chlorides from nearby water are present in the air.

Almost as corrosive as industrial environments

Warm temperatures increase the activity of corrosion elements on the surface of galvanized zinc.

Coastal proximity, wind direction and wind speed also influence the corrosion rate

Temperate marine environments

Lower temperatures and humidity make temperate marine environments less corrosive than their tropical counterparts.

As in tropical marine regions, the rate of corrosion is influenced by chlorides, distance from the ocean, wind direction and wind speed.

Suburban Environments

Less corrosive than industrial areas

Residential communities outside of urban areas and cities.

Rural Environments

The least aggressive corrosive atmosphere

Rural air and rain contain relatively small amounts of sulfur and other corrosive emissions.

ONE PART OF THE caravan that I think is often taken for granted is the chassis. I suspect this is because the chassis is not visible and in many cases is just a bit of steel.

In fact, the chassis offers several important functions. It serves as the basis for the entire caravan body and supplies both the attachment point of the trailer hitch and the attachment points of the suspension.

In Caravan World there are some technical terms associated with chassis descriptions – Box Section, RHS, DuraGal, SupaGal, Hot-Dip Galvanized etc. – and I sometimes wonder if readers understand what they actually mean. This article attempts to explain some of these terms and explore some of the more controversial issues.

Australian construction

Most caravan, motor home and fifth wheel chassis are made of steel, typically rectangular hollow section (RHS) steel. There are several specialist manufacturers such as Vic’s G&S Chassis and FP Chassis but there are also a number of caravan manufacturers who build their own and use outsourced components such as towbars and suspension components.

In general, a standard Australian built road caravan would have two 100 x 50 mm (4 x 2 inch) rails with cross pieces of either the same size or 50 x 50 mm (2 x 2 inch) steel or C section steel with punched holes welded together in a ‘box section’. In some cases, a C-profile is used as the main rail. The drawbar, or A-frame as it’s sometimes called, is either welded to the front of the chassis or runs straight back to the front suspension mounts. In a variation of this setup, the drawbar rails are actually part of the main chassis and run the full length of the van.

There may be a second chassis above that is fully welded or laminated to the bottom rails. Another variant, found in heavy off-road vans, uses 150 x 50 mm (6 x 2 inch) rails. The advantage of steel construction is undoubtedly its strength, while a disadvantage, particularly with double rail transporters, is that the weight of the steel itself becomes a design factor.

British/European construction

The British/European style chassis is very different from the Australian style as there are only two lightly constructed main rails with a drawbar and one or two cross members. The two manufacturers we’ve seen in Australia are Al-Ko (under Adria, Bailey and Swift Caravans) and BPW (under Geist Caravans).

Although many of the importers have the chassis modified specifically for this country, this form of chassis construction is often derided as unsuitable for Australian conditions. However, conditions in this country vary and for a traveler who never goes off-road, having a chassis like the Sydney Harbor Bridge is not essential.

One of the differences with this type of chassis is that the actual caravan body is often monocoque in structure, meaning it does not rely on the structural strength of the chassis. In the workshops of the former Geist importers I have seen the van body completely lifted off the chassis with no resulting damage to allow for some chassis modifications – this is not possible on most Australian built vans. An advantage of this type of chassis is that it is considerably lighter than the box section (certainly an issue in the camper world) but may not be suitable for off-road conditions.

1/4

Galvanized steel

Most caravan chassis in Australia are galvanized in some form but it is important to understand the differences. Below is an explanation of the terms used:

With hot-dip galvanizing, iron, steel or aluminum is coated with a thin layer of zinc. To do this, the metal is passed through a bath of molten zinc at a temperature of around 460 °C. When exposed to normal atmosphere, the zinc reacts with oxygen to form zinc oxide, which further reacts with carbon dioxide to form zinc carbonate. The result is a protective cover that is quite strong and prevents further corrosion of the steel underneath.

Hot-dip galvanized steel is easily identified by the steel’s crystalline patterned surface, sometimes referred to as “spangles”.

DuraGal is a proprietary process in which rectangular hollow sections (RHS) of steel are hot dip galvanized as defined above, but the outer zinc is given a surface coating to improve resistance to white rust and adhesion of paint or powder coatings. An important point is that the RHS steel is only galvanized on its outer surfaces. DuraGal steel, which must be manufactured to Australian Standard 1163, is available in two grades: C35OL0 and C45OL0.

SupaGal is very similar to DuraGal except that the RHS profiles are galvanized on both the external and internal surfaces. It’s more expensive, of course, but the owner of the process, OneSteel, believes corrosion starts from the inside and serious rust can form with no visible signs.

SupaGal is manufactured to Australian and New Zealand Standard 2312.

All of the above terms are used in relation to chassis construction, but one of these has become common and is understood to mean something other than what is implied. As can be seen above all chassis steels are hot dip galvanized but on DuraGal and SupaGal the galvanizing is done before the steel is welded which means that all welds need to be cleaned and galvanized after the chassis is erected. When the term hot-dip galvanized is used, it usually means that the hot-dip galvanizing is done after the chassis is built. As you can imagine, this process requires a much larger tank of molten zinc, so it’s more expensive and can add up to 50kg to the weight of the chassis.

Powder coated steel

Apart from some RV builders, powder coating is rarely used as an anti-corrosion measure by Australian manufacturers. However, this is not uncommon for RVs imported from the US. In short, dry powder is usually applied electrostatically to a steel component to give a relatively even finish, and then cured under heat to form a protective skin. This skin is

much more resilient than traditional paint but may not be as effective as galvanizing along Australian coasts.

aluminum

Although steel is most commonly used in the chassis construction of caravans, motorhomes and fifth wheels, there are some manufacturers who use aluminum almost exclusively. One of the main advantages of using aluminum is the reduction in weight compared to steel and the lack of e.g. B. a galvanizing for protection. The use of aluminum requires a good understanding of its properties and a great deal of skill from the craftsmen involved. Steel users are quick to point this out.

I know several manufacturers from all walks of life in the RV industry that have successfully used aluminum in their designs, including one that developed a relatively lightweight off-road van. Advocates of aluminum chassis are always quick to point to the boat and aircraft industries as examples of the successful use of aluminum, particularly in the latter case where failure of the material would be catastrophic in something like a Boeing 747.

WRAP UP

As with most things, there are pros and cons to all of the different methods, materials, and protective coatings used in chassis construction. The pros and cons are an individual matter, but hopefully you now have a better understanding of chassis terminology. It pays to be knowledgeable when you ask retailers and manufacturers the right questions about why they do what they do.

WORDS AND PICTURES Malcolm Street

Source: Carvan World June 2012

More tech articles

Electroplating is a manufacturing process that coats steel or iron with zinc. So galvanized steel is galvanized steel. There are various galvanizing processes, the most common being hot-dip galvanizing.

Advantages of galvanized steel

Galvanized steel is one of the most popular steels because it is rust resistant and less expensive than most treated steels. And it requires no maintenance or rework. Because the zinc coating protects it from the elements, the steel can last 50 years in temperate environments. Even when exposed to severe weather conditions, galvanized steel can last over 20 years.

galvanizing methods

As mentioned earlier, there are several galvanizing processes including galvannealing, pre-galvanizing, electro-galvanizing and hot-dip galvanizing. The most popular is hot-dip galvanizing, which we will discuss in more detail. But let’s briefly review the other three first.

Galvannealing: Combines hot-dip galvanizing with annealing to produce a matte matte finish that lends itself well to welding and painting.

Pre-galvanizing: The metal is primed with a cleaning agent and quickly passed through molten zinc, producing a more uniform coating than traditional hot dipping.

Electro-galvanizing: Instead of molten zinc, the steel is covered with an electrolytic solution and then an electric current is applied, which eventually binds the zinc to the steel.

What is the hot dip galvanizing process?

As the name suggests, the steel is dipped in hot, molten zinc. While the steel is in the molten zinc, a metallurgical reaction takes place between the iron contained in the steel and the hot zinc. The reaction is known as a diffusion process. In the diffusion process, the coating accumulates perpendicular to each surface, creating a uniform thickness.

When the steel is removed from the zinc bath, it reacts with the oxygen in the air to form zinc oxide. It then reacts with carbon dioxide to form the final protective layer of zinc carbonate. Finally, the steel has a corrosion-resistant, multi-layer coating of zinc metal and an iron-zinc alloy.

Hot-dip galvanized steel has a fairly distinctive appearance compared to other galvanized steels. It has a speckled, crystal-like pattern known as the “Spangle” pattern.

What is hot dip galvanizing used for?

Galvanized steel is very versatile. It is used in a variety of industries including agriculture, automotive, construction, solar, telecom and many more. Because of its resistance to corrosion, galvanized steel is preferred in applications that may be exposed to moisture or the elements.

All kinds of screws, nuts, bolts, tools and wires are galvanized to increase their durability. Entire steel frame buildings use galvanized steel to support the majority of the structure. Fences, roofs, stairs and more are often made from galvanized steel. As said, galvanized steel is very versatile! Galvanized steel offers more than enhanced functionality; it also offers an aesthetic appeal. Many architects incorporate galvanized steel into their designs. The glossy finish conveys a clean, modern feel popular in contemporary architecture.

Hot-dip galvanized vs. galvanized steel

In summary, hot-dip galvanized steel is a type of galvanized steel. The hot-dip galvanizing process is relatively inexpensive, and the resulting product is very durable and versatile. Hot-dip galvanized steel is most commonly used in applications exposed to the elements because it is highly resistant to corrosion.

How to safely weld galvanized steel

HOW TO WELDING SAFELY

GALVANIZED STEEL

Welding of galvanized steel is an important and valuable technique in the metal fabrication process – especially in the manufacture of galvanized steel wire mesh or galvanized steel mesh – but people shy away from it lately because of the toxic fumes generated when welding galvanized steel. There are also concerns about how to deal with the coating of galvanized steel and what to do about corrosion.

Fortunately, the right approach to welding galvanized steel can effectively deal with all of these problems.

Safety when welding galvanized steel

By taking the proper personal protective measures, you will be much safer when coming into contact with the toxic fumes. Different facilities may use different protective gear, although gloves, welding helmets, steel-toed boots, and sometimes leather jackets are often part of the uniform.

However, a non-negotiable protective device is the respirator. When welding galvanized steel, it is imperative that you use a respirator to avoid inhaling the potentially deadly zinc oxide fumes that are produced. Even if you use a respirator, you should weld in a well-ventilated area.

Coating problems when welding galvanized steel

Another challenge when welding galvanized steel is that zinc coatings can make a clean weld impossible, interfere with fusion, and lead to porosity and inclusions. You need an experienced welder to successfully weld galvanized steel and the ideal method is to remove the zinc coating from the area where you are welding. If this is not possible, use a filler material on the galvanized part of your weld area.

You will find that electro-galvanized steel is easier to weld than hot-dip galvanized or thermally sprayed steel, as the latter two have a thicker and less uniform coating and therefore more of a challenge to weld with zinc.

Corrosion problems when welding galvanized steel

Corrosion resistance is a problem encountered when welding galvanized steel. The whole purpose of galvanizing is to prevent corrosion, but you must remove the galvanizing zinc around the weld area and expose those areas to corrosion. The only thing you can do about it is to re-galvanize after the weld is complete. Although time consuming, this is an effective way to preserve the corrosion resistant integrity of the part.

Proper welding of galvanized steel requires some attention but is doable. Make sure all of your galvanized steel welders understand all safety rules and regulations – particularly those related to protection from toxic zinc oxide fumes. Make sure there is a standard approach to welding galvanized steel and that all your welders know how to follow it and know how to do it.

By establishing clear rules and guidelines for the safest and most effective method of galvanizing steel, you should have no problem with this important metal fabrication process.

Marco is your galvanized steel supplier

Marco Specialty Steel is your headquarters for a diverse and extensive inventory of specialty steel products, including welded galvanized steel. We stock a large range of galvanized steel products available:

Marco is your manufacturing expert

Our Houston warehouse includes a large manufacturing department that has all the necessary equipment to customize all of the products we sell.

Turn to us for your steel products

Call us for a quote on galvanized steel or other specialty steel products.

The information provided in the foregoing content may not be used to provide legal or medical advice. In terms of content, information on welding galvanized steel is to be given as a general overview. Before welding galvanized steel, you should seek expert advice.

About the author

dr Md Usmangani

1. Blogger – Specialist in analyzing scaffolding products and recommending safe quality products for construction companies. 2. Web Content Authors – 200,000 pages of SEO based website content written for various companies around the world. 3rd Author – 50+ academic and career books for school, college and university courses. 4. Editor-in-Chief – Over 6000 books and magazines published by various academic and entry-level publishers

How long will my galvanized pipes last?

It is a common misconception that any zinc coating can be called galvanizing, but in fact this is not the case as there are many different methods by which a zinc coating can be applied. Hot dip galvanizing only refers to coatings formed by immersing steel mills in molten zinc. However, there are two variants of hot-dip galvanizing: batch galvanizing and pre-galvanizing.

Batch hot dip galvanizing

This process is used to coat fully manufactured articles and involves chemical cleaning of the work pieces prior to immersion in the galvanizing bath and is specified by EN ISO 1461. This method described in this article provides complete coverage of the article (including the inner surfaces of hollow sections). there is no uncoated area. The thick coating that is formed also offers the highest possible protection against corrosion.

Product made of pre-galvanized steel

An alternative is to take a specific product (usually sheet, wire or tube) and galvanize it using an automated process.

Pre-galvanized sheet steel

This is the most common pre-galvanised product and is specified by EN 10346. The sheet is uncoiled and passed through a reducing atmosphere before being immersed in the galvanizing bath for a relatively short period of time. When withdrawing from the galvanizing bath, either an air knife or mechanical wiper is used to remove excess zinc to produce a good surface finish. However, the result is a thin coating that can vary between 7 and 42 μm depending on the grade, with most products typically having a coating thickness of 20 μm. After electroplating, the sheet is recoiled in front of a stocker, where the sheet is uncoiled and cut for sale, creating uncoated edges.

Pre-galvanized steel tubes

Tubes can also be galvanized using an automated process according to EN 10240. Again, immersion times are relatively short and on withdrawal steam can be blown through the bore of the tube to give an adequate surface finish. The coating thickness can be as low as 45–55 μm, although much of the manufactured product has a significantly thinner coating of 20–30 μm. Also for resale purposes tubes can be cut to size leaving uncoated edges.

Pre-galvanized wire

From a practical point of view wire strands may only be coated in an automated process and this can be specified by EN 10244-2. Again, immersion times are short, with wiping methods used to remove excess zinc and achieve a smooth finish. The coating thickness can vary depending on grade and strand diameter, but is typically around 20-30 μm. Note that whilst individual strands cannot be galvanized to EN ISO 1461, wire mesh could be suitable for such processing to achieve a thicker galvanized coating.

coating comparison

Both batch hot dip galvanizing and pre-galvanized coatings have different properties and the table below summarizes these.

*It is important to remember that when coating weights are given for steel sheet, the weights include both sides of the sheet, so the coating life is half that for the equivalent coating weight given in EN 10346

Learn more

You can find more information about hot-dip galvanizing on the Galvanizing Association website. Advice is also available from GA to ensure optimal component sizing.

The main difference between galvanized and hot-dip galvanized is that most galvanized materials have a smooth and sharp surface while hot-dip galvanized structures have a rough surface.

Electroplating is a process to protect metal surfaces from corrosion. After completion of the galvanizing, one speaks of a “galvanized” surface if this is done using the usual method. However, when we use a hot dip galvanized process, we call it a “hot dip galvanized finish”.

CONTENTS

1. Overview and Key Difference

2. What is galvanized

3. What is hot dip galvanized?

4. Direct comparison – galvanized vs. hot-dip galvanized in tabular form

5. Summary

What is galvanized?

A galvanized finish is a metal surface that has been coated with a layer of zinc to protect against corrosion. We call the application of this zinc layer “electroplating”. In addition, this application is made on steel or iron surfaces.

There are several types of galvanizing, including:

Hot Dip Galvanizing – Dipping the item in molten zinc

Continuous galvanizing – a form of hot dip galvanizing, but this process forms a thinner layer of zinc; thus the corrosion resistance is comparatively lower

Thermal Spray – Spraying semi-molten zinc onto the object

Electroplating – Using the item and zinc metal as electrodes in an electrochemical cell

Mechanical Plating – electroless process of depositing the coating using mechanical energy and heat

What is hot dip galvanized?

In hot-dip galvanizing, a metal is coated with a layer of zinc to protect that metal from corrosion. We can call it HDG. This process consists of the following three main steps:

Surface preparation galvanizing inspection

In the surface preparation, we need to hang the steel object with wires or put it in a suitable rack. The steel then goes through three cleaning steps: degreasing, pickling and fluxing. The degreasing step removes the dirt on the steel surface. The pickling step removes mill scale and iron oxide. Later in the fluxing step, it removes any other oxides present on the steel surface and forms a protective layer that can prevent further oxide formation.

During the galvanizing process we have to immerse the steel in a molten zinc bath that contains at least 98% zinc. Here the iron in the steel surface tends to form a series of zinc-iron intermetallic layers and an outer layer of pure zinc. In the inspection step, we need to inspect the coating. Also, we need to determine the quality of the surface zinc layer.

What is the difference between galvanized and hot-dip galvanized?

Hot-dip galvanizing is a type of galvanizing. The main difference between galvanized and hot-dip galvanized is that galvanized materials have a smooth and sharp surface while hot-dip galvanized structures have a rough surface. In addition, the process of galvanizing involves the formation of a zinc layer to protect the metal from corrosion, while hot-dip galvanizing involves the formation of a pure zinc layer on the surface of the metal through surface preparation, galvanizing and inspection.

Summary – Galvanized vs. Hot Dip Galvanized

In short, hot-dip galvanizing is a type of galvanizing. The main difference between galvanized and hot-dip galvanized is that galvanized materials have a smooth and sharp surface while hot-dip galvanized structures have a rough surface.

Relation:

1. “What Is Hot-Dip Galvanizing?” American Galvanizers Association, Available Here.

2. “Types of galvanizing and other zinc coatings.” Galvanizers Association of Australia, Available here.

Image courtesy:

1.’Image taken from page 195 of ‘The modern electroplating; a complete book giving full account of the elementary principles of electrodeposition of metals, their practical application and industrial use” (1920)” From Internet Archive Book Images (no known copyright restrictions) via Flickr

2. “Hot dip galvanizing plant 3” Oleh Sarang – Karya sendiri (Domain Publik) via Commons Wikimedia

How to safely weld galvanized steel

HOW TO WELDING SAFELY

GALVANIZED STEEL

Welding of galvanized steel is an important and valuable technique in the metal fabrication process – especially in the manufacture of galvanized steel wire mesh or galvanized steel mesh – but people shy away from it lately because of the toxic fumes generated when welding galvanized steel. There are also concerns about how to deal with the coating of galvanized steel and what to do about corrosion.

Fortunately, the right approach to welding galvanized steel can effectively deal with all of these problems.

Safety when welding galvanized steel

By taking the proper personal protective measures, you will be much safer when coming into contact with the toxic fumes. Different facilities may use different protective gear, although gloves, welding helmets, steel-toed boots, and sometimes leather jackets are often part of the uniform.

However, a non-negotiable protective device is the respirator. When welding galvanized steel, it is imperative that you use a respirator to avoid inhaling the potentially deadly zinc oxide fumes that are produced. Even if you use a respirator, you should weld in a well-ventilated area.

Coating problems when welding galvanized steel

Another challenge when welding galvanized steel is that zinc coatings can make a clean weld impossible, interfere with fusion, and lead to porosity and inclusions. You need an experienced welder to successfully weld galvanized steel and the ideal method is to remove the zinc coating from the area where you are welding. If this is not possible, use a filler material on the galvanized part of your weld area.

You will find that electro-galvanized steel is easier to weld than hot-dip galvanized or thermally sprayed steel, as the latter two have a thicker and less uniform coating and therefore more of a challenge to weld with zinc.

Corrosion problems when welding galvanized steel

Corrosion resistance is a problem encountered when welding galvanized steel. The whole purpose of galvanizing is to prevent corrosion, but you must remove the galvanizing zinc around the weld area and expose those areas to corrosion. The only thing you can do about it is to re-galvanize after the weld is complete. Although time consuming, this is an effective way to preserve the corrosion resistant integrity of the part.

Proper welding of galvanized steel requires some attention but is doable. Make sure all of your galvanized steel welders understand all safety rules and regulations – particularly those related to protection from toxic zinc oxide fumes. Make sure there is a standard approach to welding galvanized steel and that all your welders know how to follow it and know how to do it.

By establishing clear rules and guidelines for the safest and most effective method of galvanizing steel, you should have no problem with this important metal fabrication process.

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The information provided in the foregoing content may not be used to provide legal or medical advice. In terms of content, information on welding galvanized steel is to be given as a general overview. Before welding galvanized steel, you should seek expert advice.