The second phase of an LCA examines the additional material and energy inputs and emission outputs generated while a product is in use. As shown in the Time to First Maintenance chart (Figure 4), hot-dip galvanized steel requires no maintenance for 75 years or more. Consequently, hot-dip galvanizing accrues no additional environmental impact throughout its service-life. While hot-dip galvanizing’s environmental impact is isolated to the production phase, the environmental impact of other coating systems, such as paint, increases during use (Figure 13). Paint, which must be maintained repeatedly throughout use, generates additional environmental impact during each maintenance cycle.
Paint coatings require regular maintenance on a predetermined cycle of 12-20 years. P1, P2, P3, and P4 (Figure 14) represent the additional environmental costs associated with the maintenance of painted steel. Therefore, a project with a targeted 60-year life will require at least two to four maintenance paintings. Each maintenance-cycle (whether touch-up, maintenance, or full repaint), will require additional energy and material inputs and generate emissions and waste outputs. Furthermore, there are indirect environmental costs associated with conducting maintenance, such as additional exhaust due to traffic delays/detours when maintaining a painted steel bridge.
