A coating system with low maintenance will often give lower life cycle costs, in spite of higher costs in the new construction phase. The Public Roads Administration in Norway has been using coating systems consisting of thermally sprayed zinc and a paint system, so called duplex coatings, since 1965 with very good results. Road bridges are constructions with lifetime typically in the order of 100 years, which usually means that maintenance will completely dominate the life cycle cost analysis. They have examples of steel bridges in corrosive coastal areas where the duplex coating system has been providing corrosion protection for more than 40 years without any maintenance. The paper discusses degradation, maintenance and life cycle costs for various offshore coating systems, both for the oil and gas industry and offshore wind energy farms. The analysis is based on the experiences from the Norwegian Public Roads Administration and from experimental investigation of coating systems in lab and field tests.
For constructions with a long lifetime the maintenance costs should be taken into consideration when selecting protective coatings. Offshore coating maintenance is expensive, whether it is structural steel, pressure containing equipment, platforms or wind turbines. In addition the limited control of climatic conditions decreases the quality of the applied maintenance coating. Thus the repair coating will have a shorter lifetime than the original coating. Coating systems with longer lifetime that requires less maintenance may then be beneficial in a life cycle perspective. Saving money in the construction phase may not give the best economy in the long run. In this paper we argue for more use of thermally sprayed zinc (TSZ) with a protective paint system on top, especially for long life constructions or constructions where maintenance is difficult and expensive.
