In general, life-cycle cost analysis compares the total cost of one financial option with one or more alternatives. Specifically, LCC enables structure owners and specifiers to evaluate the costs of competing coating options on the basis of both price and effectiveness.
The true cost for all candidate coatings, painting, galvanizing, or metalizing should include the direct costs for the initial coating application, subsequent maintenance costs, and the costs to the public for loss of use at the initial coating, and at the time of all future maintenance.
The British Standard addresses the comparative of cost of one coating option versus another in Appendix E.
Choosing the most economical defence against corrosion77
The choice of the most economical defence against corrosion cannot be precise, because neither the timing nor the cost of future maintenance can be predicted accurately and rates of taxation change from time to time. Nevertheless, an overall economic appraisal should be made, for it may help to influence a decision when there is uncertainty regarding the choice of protective system or products that require a protective system.
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A quick comparison of systems can be made by comparing present first costs plus maintenance costs at present values in each case. (Access and disruption costs should be taken into account at this stage.)
The FHWA report RD-01-156 referred to earlier points out that disruption costs are to be included in the life-cycle cost analysis and will be significant:
Life-cycle [cost] analysis estimates indirect costs to the user due to traffic delays and lost productivity at more than 10 times the direct cost of corrosion maintenance, repair, and rehabilitation.78
The value of these indirect costs, traffic delays, etc. may actually be incalculable but we know it is significant. Including these costs in the comparison of paint versus metalizing favors the coating with the longest possible service life - metalizing. And anyone who has sat in a long line of cars beside miles of a painting contractor’s orange traffic barrels appreciates the importance of using protective coatings with the longest possible maintenance interval.
In the case of painting or metalizing structural steel, the life-cycle cost considers the sum of all costs for each of the coating options distributed over the surface area coated, and then distributes them over time, the service lives of the several coatings; ten years, twenty years, forty years, etc. It may be said that the competing costs are normalized as dollars, per square foot, per year. This is a well reasoned basis for comparing the alternatives and, presumably, the bridge owner will select the coating that will make the best use of taxpayers’ money.