This paper is a significant update to “Costing Considerations for Maintenance and New Construction Coating Work”1 on protective coating costing and selection co-authored by M. F. Melampy, M. P. Reina and K. R. Shields in 1998. Designed to assist the coatings engineer or specifier in identifying suitable protective coating systems for specific industrial environments.
Coatings are widely used to mitigate corrosion of structural steel in aggressive humid environments. Zinc-rich primer three-coat paint systems are widely used to mitigate corrosion of steel bridges. However, the associated costs of its required maintenance are high. As part of a research program, chemically bonded phosphate ceramics (CBPC), thermal diffusion galvanizing (TDG) and metallizing coatings along with the current 3-coat systems were exposed in outdoor conditions for up to 2 years and in salt-fog exposure for up to 14,600 hours.
Corrosion protection of infrastructure and assets is an area of increasing focus due to increasing financial and safety concerns. On a global scale, corrosion has an annual cost of $2.5 trillion (USD).1 To combat the deleterious effects of this natural phenomenon, specifiers and owners have many choices in terms of materials and protective coatings. Consideration of both initial and life cycle costs has become more important in the age of increased competition and shrinking maintenance budgets.
Major manufacturers of protective coatings, steel fabricators, painting contractors, galvanizers, and end users, were surveyed to identify surface preparation and coating application costs, coating material costs, typical industrial environments and available generic coatings for use within those environments, and expected coating service lives (practical maintenance time).
Engineers, architects, DOTs, and other specifiers use hot dip galvanizing to provide corrosion protection to steel and iron in many industries, including transportation and highway, parking garages, bridges, structural, agricultural, petrochemical, and original equipment manufacturing. To ensure continued corrosion protection and structural integrity in these industries, it is necessary to properly inspect the galvanizing.
Corrosion is a natural phenomenon, and thus can never be completely eliminated; however, it is a misconception nothing can be done. Estimates show 25-30% of steel corrosion could be eliminated if proper corrosion protection methods were employed. Corrosion can simplistically be viewed as the tendency for the metal, after production and shaping, to revert back to its lower, more natural energy state of ore. This tendency is known as the Law of Entropy.