"Expected Service Life and Cost Considerations for Maintenance and New Construction Protective Coating Work" has been published and presented bi-annually at legacy NACE International Conferences since 1998 and has become one of the most referenced documents for conducting comparative lifecycle costing of protective coating systems across various structures and service environments. However, practical application of the data can be challenging.
This paper and presentation provide examples of how to determine the expected service life and maintenance painting sequence and calculate life cycle cost to examine various coating options for industrial painting projects. The service life and cost data are based on the most recent update to the white paper "Expected Service Life and Cost Considerations for Maintenance and New Construction Protective Coating Work," co-authored by J. L. Helsel and R. Lanterman, which was presented at the AMPP 2022 annual conference.
The sample projects include a new bridge structure and an existing chemical production facility. Various coating systems are selected for evaluation, with the expected service life of candidate systems based on the assumed maintenance painting sequences. The life cycle costs are estimated based on the forecasted service life of the coating systems, the prevailing service environment and design life of the structure/facility. The examples will illustrate how different circumstances affect the life cycle cost tradeoffs.
For each sample project, the service environment (i.e. exposure conditions) and anticipated maintenance painting sequence needs to be defined. The service environments correspond to ISO† 12944-2, "Classification of Environments."
The referenced paper (referred to as the Paper) presents a sequence for typical maintenance painting. This sequence includes the follow steps:
• Original Painting
• Spot Touch-Up and Repair (1 or 2 cycles)
• Maintenance Repaint [spot prime and full coat] (1 or 2 cycles)
• Full Repaint [total coating removal and replacement]
Often, multiple cycles of touch-up and/or maintenance repainting can be performed prior to the need for full repainting. The determining factors involved are the amount of corrosion present and the physical characteristics of the existing coatings. The maintenance painting sequence is assumed to begin at the Practical Maintenance Time (PMT), which is defined as the point where the original coating system has 5 to 10% coating breakdown and/or corrosion of the substrate. The PMT, in years, is provided in Table 1A of the Paper for different ISO service environments. Once the coating systems being considered for a project are defined, the timing and number of maintenance steps can be determined based on the assumed sequence and life of the structure being maintained.
