galvanizing case studies

Case Study: Industrial Facility

The construction of four buildings comprising a solid-waste recycling facility for the city of Chicago creates a perfect case study for the selection process of a corrosion protection system. In this case, the selection process compared the use of hot-dip galvanizing to paint.

The original specifications of the Calumet industrial facility called for:

• 7,400,000 lbs. (3,356,854 kg.) of structural steel
• 470,000 sq.ft. (43,664 sq.m.) of building
• Three-coat epoxy paint

Driven by the design engineer who was familiar with the benefits of hot-dip galvanizing, and a fast-track schedule that would make painting a potential delaying and cost-increasing factor, the contractor offered a substantial rebate to the city if the specification was changed to galvanizing. The final specification was changed to 7,400,000 lbs. (3,356,854 kg.) of galvanized structural steel. Further examination of the decision to galvanize showed hot-dip galvanizing to be:

• lowest in original cost
• the lowest life-cycle cost for this facility

The city of Chicago is the beneficiary of the decision to galvanize. The project was delivered on schedule and for less money than a painted facility would have been.
Additional benefits to the city in specifying galvanizing include:

• extremely low field touchup cost
• 48-hour turnaround time for steel to be galvanized
• no maintenance requirements for decades

The engineers and contractor readily admit that the project simply could not have been built on schedule and within budget had hot-dip galvanizing not been specified. For the city of Chicago, galvanizing does cost less and last longer.

Case Study: Power Plant

Puerto Rico's newest power plant was to be located in a corrosive environment just 500 yards from the Caribbean Ocean and in a moderately industrial setting. The plant including a turbine building and two coal-fired burners was initially specified to be painted. It was only after diligent efforts by the galvanizer, fabricator and design team that the owner reconsidered the decision to apply a two-coat paint system and, ultimately, opted to galvanize the steel used in the construction.

Original considerations included:

• Over 10,000 tons (9,072 metric tonnes) of steel would need to be fabricated and erected
• The fabrication items were a mix of heavy, medium and light structural steel, averaging 350 sq. ft./ton (36 sq.m./metric tonne), including thousands of miscellaneous plates, angles and connection pieces
• Permit issues and Hurricane George led to a three-year project construction delay
• The final fabrication and painting schedule was undetermined until just before drawings were released for construction
• Cold and wet weather were variables to be considered in the installation and painting process

The final determination had not yet been made whether to apply the two-coat paint system in the fabrication shop or to apply the primer in the shop and top-coat in the field
Thousands of loose plates, angles and connection material required coating, assembling, packaging and shipping
Hundreds of beams and braces had ten or more plates attached to each end.
Roll-on/roll-off trucking and shipment by barge would be utilized

The galvanizer encouraged the engineer and owner to consider not only the initial cost data, but also the life-cycle cost data for the originally specified shop primer and field topcoat paint system, and the two-coat shop-applied system.

The material and labor cost data included in the National Association of Corrosion Engineers paper #477, Costing Considerations for Maintenance and New Construction Coating Work, 1996, was used to compare to the initial and life-cycle costs for hot-dip galvanizing. In addition, the physical and logistical advantages of galvanizing were presented for consideration by owners, fabricators and design teams. The resulting overview and decision to galvanize the structural steel presented the owner with a win/win position both economically and in scheduling fabrication and erection.

Reasons for Selecting Hot-Dip Galvanizing

The life-cycle cost of galvanizing versus paint dictated a clear direction for this project. The durability of galvanized steel during shipment, erection, and throughout the lifetime of the structure was evident. In addition, the ability to galvanize material 365 days a year with quick turnaround time (measured in hours, not days) made galvanizing the most practical and economical choice. Specifically:

Hot-dip galvanizing, based on life-cycle cost, was an impressive 34% of the cost of a shop primer only. A field-applied top-coat would present higher cost, create delays in final erection and limit access for other trades to complete construction.
Hot-dip galvanizing, when compared to the alternative two-coat shop-applied paint system, was just 16% of the cost on a life-cycle basis.
Galvanizing is done independent of the weather and would provide corrosion-protected fabrications to the job site within hours of receipt of the black steel at the galvanizer's facility. Even under ideal weather conditions, the three to four days required to shop-apply the two-coat paint, allow for drying time, and reassemble and load with particular caution would not meet schedule demands.

Galvanizing economically handles parts and fabrications of all sizes throughout the process. In particular on this project, all of the fabrications were welded or loose-bolted prior to shipment to the galvanizer, thus eliminating the reassembly of parts and reduction of lost and missing parts. Thousands of fabricated members had an unusual number of loose pieces that would have required painting and drying prior to assembly. The logistical details and shop floor-space requirements made painting impractical and imposed hidden costs on the fabricator.

Galvanized steel is durable and requires little, if any, shop or field touchup. The tight schedule would not allow the extensive and expensive touchup required of painted steel that would have been shipped in roll-on/roll-off trailers (requiring extensive tie-down, wrapping and loading standards in order to protect painted material), barged, and erected.
For a practical maintenance plan in the first 25 years of the project, the life-cycle costs for galvanized steel in the power plant would be nearly nonexistent. When the time-value of money, repair costs, and shutdown costs were evaluated for a painted steel plant, the decision to galvanize proved to be the most economical.

The owner, fabricator and design firm all agree that making the decision to galvanize the power plant steel was key in delivering an operational plant on best possible schedule and within budget. Additionally, they are convinced that the life-cycle costs to maintain the galvanized steel will be so minimal over the next 20 - 30 years and the shutdowns to repair so infrequent, that their decision will provide additional profit for generations to come.

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