Evaluation of corrosion inhibitive coatings
Is there a commercially available inhibitive-type coating system that delivers similar performance to the modern day systems that we currently specify? Up until this point, Reclamation has focused its work on barrier immersion coatings, not inhibitor coatings for severe atmospheric service. Reclamation's legacy coatings like lead-based alkyds and chromates contained inhibitive properties and provided service lives of upwards of 80 years. Modern inhibitor coatings have been largely untested by Reclamation, and it is unknown how they would compare to Reclamation's barrier coating systems and legacy systems.
Need and Benefit
Modern coating systems specified for use on Reclamation's steel structures do not last nearly as long as legacy
coatings like lead-based alkyds, coal tar enamel, and chromate-based coatings. Therefore, use of modern coating
systems elicit more frequent maintenance and repair of vital structures. With increasing labor and material costs,
aging facilities have to spend much more than before to perform corrosion prevention maintenance and structures
need to be taken out of service more frequently.
Reclamation has traditionally focused its testing on barrier coatings whereas legacy coatings like lead-based alkyds
are inhibitor coatings. Additionally, Reclamation's coating research focuses primarily on coating systems suitable for
immersion exposure and has not performed much analysis of coatings for severe atmospheric exposure.
A literature review conducted in 2017 analyzed the mechanisms that give lead-based coatings excellent corrosion
protection properties. These mechanisms are based on inhibitive pigments that react in the presence of an electrolyte
and inhibit corrosion through passivation or by forming metal soaps. Unlike barrier coatings that passively act as an
obstacle to block the electrolyte from reaching the metal substrate and causing corrosion, inhibitive coatings actively
prevent corrosion by stunting or polarizing the reaction.
With gate recoatings exceeding $1,000,000, a full rehabilitation is not economically feasible at 20-30 year intervals
(the average service life of coating systems currently specified by Reclamation). This study could identify one or more
coating systems that have service lives that are two or three times as long as currently used systems. In addition, the
structures will not have to be taken out of service as frequently which could increase the energy-generating time.
Considering Reclamation has 492 dams, the long term savings of lowered life cycle costs could near $1 billion.
Reclamation's infrastructure is aging and limitations in coatings technology means we currently don't have the ability
to keep up with all of the repair and maintenance needs. If we don't find a way to improve the corrosion protection on
our structures, costs will increase significantly and we face the possibility of losing irreplaceable and vital infrastructure
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