Case study: Louis Armstrong New Orleans International
The new Louis Armstrong New Orleans International Airport, Louisiana, opened in the fall of 2019. The $1-billion project included the construction of 35 gates, increased security, and a 2200-car parking garage. Visitors and passengers arriving at the airport will be welcomed by the aesthetically pleasing white canopies, supported by HDG tubular steel frames top-coated with paint. The designers chose HDG steel because of its sustainability and ability to meet the requirement of a 50-year life with low maintenance cost. However, they also wanted precise control of the aesthetics of the HDG tubular frame supports to exactly match the appearance of the canopies. In instances where corrosion resistance and durability cannot be compromised, a duplex coating (HDG steel along with paint/powder-coating) is often chosen, as it provides the best of both worlds for the specifier: superior corrosion resistance and desired aesthetics.
Duplex systems also have the added advantage of extending the time-to-first maintenance for the paint. Galvanized coatings are as a better substrate for paint than bare steel because zinc corrodes at approximately 1/30th the rate of bare steel, thus slowing under-film corrosion. When using these two systems in tandem, the typical repetitive, scheduled maintenance for paint on bare steel will be reduced, and no unsightly paint peeling or rust bleeding will occur. The duplex system will protect the steel panels from the inside out, while allowing the bright coloring consistent with the architect’s vision to exist free of corrosion.
Conclusion
Appearance concerns regarding after-fabrication, batch, hot-dip galvanizing can be avoided with proper communication between the design professional, fabricator, and galvanizer. Depending on the final intended use of the HDG steel, a strategy can be developed between the parties to ensure the highest coating quality is achieved whilst preserving the superior corrosion protection provided by HDG steel.
Alana Fossa is the senior corrosion engineer for the American Galvanizers Association (AGA) and the vice-chair of the ASTM Subcommittee A05.13 that authors and edits specifications on hot-dip galvanizing of steel articles. Fossa provides assistance to architects, engineers, fabricators, owners, and other specifiers regarding technical issues and the processing of hot-dip galvanized (HDG) steel. She also manages AGA studies and research on performance, application, and processing of HDG steel. She can be reached at afossa@galvanizeit.org.
John Krzywicki has worked for the American Galvanizers Association (AGA) for six years, starting as a corrosion engineer and eventually being promoted to marketing director. His strong engineering background provides him with the technical knowledge necessary to effectively communicate design, performance, and sustainability considerations when using hot-dip galvanized (HDG) steel. He can be reached at jkrzywicki@galvanizeit.org.
