Once the metal is cleaned, treated, and painted, the strip is rewound into a coil size prescribed by the customer. From there, the coil is removed from the line and packaged for shipment or additional processing.
After the primer is applied and cured, then the metal strip enters the finish coat station where a topcoat is applied. Topcoats provide color, corrosion resistance, durability, flexibility and any other required physical properties. Like primers, the topcoat is cured using thermal cure ovens.
Oven
Coil coating ovens can range from 130 feet to 160 feet and will cure the coatings in 13 to 20 seconds.
During this stage, the strip enters the prime coat station whereby a primer is applied to the clean and treated metal. After the primer is applied, the metal strip travels through a thermal oven for curing. Primers are used to aid in paint adhesion, improve corrosion performance and enhance aesthetic and functional attributes of the topcoat.
S Wrap Coater
The S wrap coater design allows for primers and paints to be applied to the top and back side of the metal strip simultaneously in one continuous pass.
The cleaning and pretreating section of the coil coating process focuses on preparing the metal for painting. During the cleaning stage, dirt, debris, and oils are removed from the metal strip. From there, the metal enters the pretreatment section and/or a chemical coater whereby chemicals are applied to facilitate paint adhesion and enhance corrosion resistance.
Dried-In-Place
In this stage a chemical that provides enhanced corrosion performance is applied. This treatment can be chrome free if required.
The accumulator is a structure that adjusts up and down to store material, which makes continuous operation of the coil coating process possible. This accumulation will continue to feed the coil coating processes while the entry end has stopped for the stitching process. As much as 750 feet of metal can be collected.
Hot-Dip Galvanized Steel Offers Superior Initial and Long-Term Economic Advantages
Sometimes thought to be more cost prohibitive, at least initially, than other corrosion protection solutions, the American Galvanizers Association (AGA) has conducted a cost case study wherein the initial and lifecycle costs of hot-dip galvanized steel were compared to other methods. Let’s take a look at the findings.
AGA Cost Case Study
The parameters:
Typical mix of steel shapes/sizes
50,000 square foot short-span bridge
75-year design life
Moderately Industrial (C3) Environment
Using the AGA Life-Cycle Cost Calculator, a quantitative analysis was conducted comparing hot-dip galvanizing to four paint systems, as well as a duplex system and metallizing with defined maintenance schedules.
Initial Cost:
Including materials (paint, metallizing, etc.), the number of coats, the surface prep cleaning method (painted systems: SP-10; duplex: SP-16/ASTM D6386; metallizing: standard near white metal), where the application was performed, and labor costs versus galvanizing’s all-inclusive price:
Coating System
$/ft2
Total
Hot-Dip Galvanizing
$1.76
$ 88,000
Epoxy/Epoxy
$2.92
$ 146,150
Epoxy/Polyurethane
$3.35
$ 167,650
Inorganic Zinc/Epoxy
$3.17
$ 158,650
Inorganic Zinc/Epoxy/Polyurethane
$4.53
$ 226,300
Galvanizing/Epoxy/Polyurethane (Duplex)
$5.28
$ 263,950
Metallizing
$8.37
$ 418,550
These findings indicate that when all the costs are considered, galvanizing is often less expensive and at the very least, exceedingly competitive with other coating systems.
Life Cycle Cost:
Utilizing a practical maintenance cycle over the prescribed 75-year lifetime of the project based on Net Future Value (NFV) and Net Present Value (NPV) calculations at 3% inflation and 2% interest, and accounting for a very unlikely needed maintenance paint with an inorganic zinc at year 70 for the galvanized steel:
Coating System
$/ft2
Total
Hot-Dip Galvanizing
$ 4.29
$ 214,500
Galvanizing/Epoxy/Polyurethane (Duplex)
$22.84
$1,142,000
Inorganic Zinc/Epoxy
$39.92
$1,996,000
Inorganic Zinc/Epoxy/Polyurethane
$41.53
$2,076,500
Epoxy/Epoxy
$51.91
$2,595,500
Epoxy/Polyurethane
$61.63
$3,031,500
Metallizing
$62.80
$3,140,000
Even with the one maintenance cycle near the end of the life of the project, hot-dip galvanizing was proven to have a significantly more economical lifecycle than that of the other coating systems.
Galvanized Steel Protects Your Investment
To maximize return on investment, it’s critical that buyers ensure the longevity of their purchase. Enhanced over 200 years, galvanizing is a process that best protects steel for long-lasting, corrosion-free performance. In fact, galvanized components can potentially last up to a century without the need for costly maintenance, delivering a significantly lower lifecycle cost, especially when compared to alternatives like stainless steel, aluminum, and epoxy coating. And research suggests that non-galvanized structures incur indirect costs as much as 11 times higher than those that utilize galvanized products. In an economy where steel prices are expected only to rise, buyers are wise to protect their investment and achieve cost savings by galvanizing.
GalvXtra Hot-Dip Galvanizing
AZZ’s GalvXtra four-step, hot-dip galvanizing process uses a proprietary formulation of molten metals to deliver consistent, high-quality zinc coatings on ferrous materials. At the preparation stage, steel arrives at AZZ’s galvanizing plant and is inspected to ensure that drainage and venting requirements are met. Then, the metal is cleaned by immersion in a hot alkali solution, acid pickled to remove rust or scale, and fluxed to eliminate surface oxides. Next, the steel is hot-dip galvanized—submerged in a bath of molten zinc to form a shield of zinc/iron intermetallic layers on all surfaces. Finally, the newly galvanized steel is cleaned, weighed, and carefully inspected with calibrated instrumentation to ensure quality standards.
Trust Your Steel to AZZ
AZZ performs hot-dip galvanizing for steel components used in a wide range of applications, including agriculture, bridge & highway, construction, electrical utility, industrial, original equipment manufacturers, petrochemical, recreational, and transportation. Backed by 60 years of experience in the materials industry, AZZ offers exceptional galvanizing service at over 40 locations across the U.S. and Canada. Click to learn more about protecting your steel investment.
Hot-dip galvanizing is a trusted solution for long-lasting corrosion protection, relied upon for its durability and unmatched performance. This video provides a step-by-step look at the galvanizing process, showcasing how steel is transformed with a protective zinc coating that stands up to the toughest conditions. From surface preparation to the final finish, see how this process ensures strength and longevity for projects of all sizes.
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