Time to First Maintenance
The Time to First Maintenance (Figure 7) for hot-dip galvanized coatings in atmospheric exposure is linear to the zinc coating thickness. Time to First Maintenance is defined as the time to 5% rusting of the substrate steel. Structural steel pieces that are ¼-thick or greater are required to have at least 3.9 mils of zinc, according to the specification. As the TFM Chart shows, this would equate to 72-73 years of life before maintenance in an industrial environment.