Abstract
Public infrastructures like bridges typically have a design lifetime of 100 years or more. When selecting protective coatings in such a long term perspective, focus should be on life cycle costs and not only the costs in the construction phase, since the maintenance costs may be considerable and dominate the total cost of ownership. Coating selection standards like ISO 12944 are not intended for such a long timescale, and there is little documentation in the literature of coating performance with lifetimes of more than about 20 years. Owners of structures with very long lifetimes have little information to base their coating selection on, besides their own experiences. Thermal spray zinc (TSZ) duplex coatings have been shown to be highly durable, as evidenced by more than 50 years of successful use since first specified by the Norwegian Public Roads Administration (NPRA). The paper will summarize field examinations, maintenance costs, coating lifetime expectations and life cycle cost estimates for steel bridges as a function of the environmental corrosivity category (C1-C5) and make comparisons to alternative coatings that are less expensive to apply but that have shorter lifetime expectancy.
