Organisms exist in every natural environment and have known impacts on coating performance and failure, such as marine bio-foulers, mold or fungi in humid terrestrial or aerial environments, or organisms involved with microbiologically influenced corrosion. These studies have shown that the organisms are capable of settlement and proliferation on nearly any surface, accelerate traditional corrosion and chemical degradation processes, and persist even after harsh physical or chemical cleanings that also cause coating material deterioration/loss. This can cause more frequent surface cleanings, prematurely fail protective coatings, compromise structural integrity, and influence coating re-application frequency and long-term adhesion.
Typical approaches to mitigate biological settlement include the use of biocides/fungicides with a loading/leach rate that will deter biological accrual. However, over the coating’s service life and under exposure to an array of environmental conditions, organism settlement still occurs. Eventually, the coating is cleaned either chemically or physically to remove organisms from the surface of the coating. Recent research has found that superficial cleanings of surfaces in both Air Force and Army applications do not fully address biological interaction with coatings. Organisms still remain on surfaces regardless of how recently they had been cleaned. This is also applicable to marine organisms. Underwater hull cleanings are required more frequently after the initial cleaning, and this phenomenon is still not well understood.
Fundamental knowledge gaps still exist within the area that prevent technology transition and long-term resolution of biological settlement and deterioration—in particular, the rate of bio-deterioration, either directly or through surface cleanings, and the successive impact on coating performance. Most previous research has focused on single organisms in unrealistic environments and there are no standard assays developed to provide a surrogate of performance deterioration rates due to biological activity. Resulting studies from this SON will guide future coating formulation design and testing, determine suitable preventive measures and material selection, and enable more accurate prediction of coating cleaning, failure, and re-application rates. Tri-service environmental impacts include informing maintenance procedures (e.g., cleaning/re-coating), potentially reducing re-coating and cleaning frequencies, determining appropriate coating biocide/fungicide loading, and informing environmental regulations regarding biocide/fungicide toxicity, fate, and transport.
