Am I (customer) being charged for thick coatings? Why do I keep getting thick coatings from the galvanizer&#; are they trying to inflate the total selling price by putting more zinc on the steel?

This is a question the AGA receives from time to time over concerns related the thickness of the hot-dip galvanized coating. Although sometimes a thick coating can be desired to achieve greater longevity of the hot-dip galvanized coating, other times an excessive coating thickness potentially results in issues related to fit-up between parts, appearance concerns, or flaking of the coating.

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However, it is not true that galvanizers provide thick coatings in an attempt to charge more for their services on a per-pound basis. Zinc is the largest material cost factor in the hot-dip galvanizing process, and thick coatings result in lower profit margins. If we look at the cost of zinc used in the hot-dip galvanizing process, it is possible to see the impact zinc prices and thick coatings have on the galvanizer&#;s bottom line.

Prices of zinc over the last year (USD):

• 52-week low: $1.04/lb
• 52-week high: $1.64/lb
• Current: $1.19/lb

Galvanizers charge for their services by weighing the part after it has been galvanized, and this results in pricing anywhere from $0.20 to $0.50 (USD) per pound of finished weight. This pricing information is general to the industry in North America and based on survey data obtained from AGA galvanizing members. Though an increase in coating thickness adds extra weight (and therefore cost) to the final product, the zinc prices referenced above mean the galvanizer actually loses $0.69 to $0.99 for each additional pound of zinc on a part which is beyond the minimum needed to meet the specification requirements. This explains why it is not in the galvanizer&#;s best interest (financial or otherwise) to provide excessively thick coatings. Instead, the galvanizer&#;s profit margins increase when the minimum average coating thickness is met while overall zinc consumption is minimized.

Then why does the galvanizer occasionally provide thick coatings when it is not desired by either the galvanizer or the customer? The primary challenge occurs when the customer provides the following types of steels or steel assemblies that make limiting the coating thickness very difficult. The list below contains links to additional Dr. Galv articles explaining why these conditions may result in thick coatings:

When specifying these steels or assembly types, there are some methods the galvanizer can employ to try and limit the coating thickness. It is important to note not all of these methods may be applicable to a project, and a thinner coating is never guaranteed:

• Reduce immersion time
• Request the customer blast clean the parts before hot-dip galvanizing
• Move/agitate the part as much as possible while immersed in the bath
• Increase immersion rate and decrease withdrawal rate from the zinc bath (effectiveness limited by poor venting/drainage design)
• Add elements to the zinc bath known to reduce the surface tension of the zinc and/or reduce reactivity for Sandelin Steels with 0.04 &#; 0.15 % Si content (impractical to change existing bath chemistry for one customer)
• Lower the bath temperature (often impractical)

In order for these methods to be used successfully, steel chemistry and/or assembly make-up should be provided to the galvanizer ahead of time in order to evaluate the steel chemistry, review the overall design, and then determine which measures are appropriate to limit the coating thickness.

To avoid future concerns about thick coatings and pricing in the future, direct communication with the galvanizer is critical to ensure a successful combination of design, fabrication, and galvanizing practices are employed. These practices help ensure your expectations are met regarding cost, fit-up, appearance, and overall quality. 

Home » Hot-Dip Galvanizing (HDG) » What is the Cost of Galvanized Steel?

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What is the Cost of Galvanized Steel?

Many specifiers have the perception hot-dip galvanized steel is cost prohibitive on an initial cost basis in comparison to other forms of corrosion protection.  This likely stems from a number of things including the fact galvanizing is viewed as a Cadillac system because of its maintenance-free longevity.  However, due to the relatively stable price of zinc and technology /process efficiencies in the last 20 years, hot-dip galvanizing has steadily become more competitive, and often less expensive, on an initial basis than other corrosion protection systems.

Many other corrosion protection systems, such as paint and powder coatings, have seen cost increases of 100% or more in the past five years.  And to add salt to the wound, these other protective systems require maintenance on a more frequent basis, increasing the life-cycle costs.  Direct maintenance costs for any project are typically 2-5 times the initial cost, and the indirect costs are even worse 5-11 times the direct cost of repair.

Because of the escalating cost of other coating systems and the astronomical costs of maintenance, more specifiers have begun to consider life-cycle costs when selecting their building materials.  Life-cycle cost (LCC) is a more complete analysis because it considers the total cost over the life of the project (initial + maintenance).  Because hot-dip galvanized steel requires no maintenance for 70 years or more in most environments, often the initial cost is the life-cycle cost meaning hot-dip galvanized steel is 2-6 times more economical over the expected life of a project making it a sustainable choice for today and tomorrow. 

Therefore, when specifiers are selecting materials for a given project, it is paramount to consider more than just the initial cost of a protection system. Taking into account the overall service life, expected time to first maintenance, and corresponding economics related to the initial and continued upkeep provides a more accurate prediction of the projects impact on future generations. 

Projects are complex and comprised of different steel sizes and quantities.  Furthermore, location, as well as differently sized kettles, equipment, and other efficiencies within galvanizing plants all affect the cost structure of galvanized steel.  For this reason, your local galvanizer is best suited to assist you with pricing for your specific project.

101 Freeway Overcrossing in Los Angeles uses a duplex system of galvanized steel and a painted stencil pattern to give the spangled look

However, if you are interested in getting an idea of the cost differences initially and over the life cycle of hot-dip galvanized steel and other coating systems, the American Galvanizers Association (AGA) has developed an online Life-Cycle Cost Calculator (LCCC).  The LCCC automates the calculation found in the specification ASTM A and allows you to compare the initial and life-cycle cost of hot-dip galvanizing to 30+ other corrosion protection systems. The Life-Cycle Cost Calculator uses data from a KTA Tator, Inc. survey of paint manufacturers as reported in NACE Paper No C- Expected Service Life and Cost Considerations for Maintenance and New Construction Protective Coating Work () and a nationwide survey of AGA members.

To use the calculator, you input the specific parameters of your project (real or hypothetical) in three quick screens, and then the LCCC will provide a customized, printable comparison of initial and life-cycle costs of galvanizing to your selected corrosion protection system. Alternatively, you can compare a duplex system (hot-dip galvanizing and paint) to paint systems.  Duplex systems require a lot of initial investment, as you are paying for both coatings up front.  However, when evaluated on a life-cycle basis, duplex systems provide huge economic savings because they require less maintenance throughout the life of a project than painted black steel.

Launch the Galvanizing Cost Calculator

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