Abstract
There is a rising imperative to increase the operational availability of maritime vessels by extending the time between full docking cycles. To achieve operational efficacy, maritime vessels must remain clear of biological growth. Such growth can cause significant increases in frictional drag, thereby reducing speed, range and fuel efficiency and decreasing the sensitivity of acoustic sensors. The impact that various stages of fouling have on acoustic equipment is unclear. It is also unclear to what extent antifouling techniques interfere with the transmission of acoustic signals. In this study, to examine this effect, neoprene samples were coated with three antifouling coatings, namely, Intersmooth 7460HS, HempaGuard X7 and Hempasil X3. Other neoprene samples were left uncoated but were imbedded with the biocide, 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) during the mixing and curing process. Uncoated nitrile samples that had varying levels of fouling from immersion in Port Phillip Bay, Australia, for 92, 156 and 239 days were also extracted. The acoustic properties of these samples were measured using an acoustic insertion loss test and compared to uncoated neoprene or nitrile to ascertain the acoustic effects of the applications of antifouling coatings as well as the fouling growth itself. A T-peel test was performed on all coated samples in an attempt to understand the adhesive properties of the coatings when applied to neoprene. It was found that the application of antifouling coatings had little effect on the transmission characteristics of the neoprene with approximately 1 dB loss. The embedment of DCOIT, however, has a chance of causing aeration in the neoprene, which can heavily hamper transmission. An assessment of the effect of the fouling growth found that light and medium fouling levels produced little transmission loss, whereas more extreme fouling lead to a 9 dB transmission loss. The adhesion properties of the coatings were investigated but not fully ascertained as tensile yielding occurred before peeling. However, various failure modes are presented and discussed in this study.
Highlights
Fouling is the accumulation of unwanted substances, such as proteins molecules and organisms, on marine infrastructure such as pylons, boats or pipes due to exposure to their environment [1,2].As fouling accumulates, it can have many adverse effects including increasing drag, reducing the Polymers 2019, 11, 663; doi:10.3390/polym11040663 www.mdpi.com/journal/polymersPolymers 2019, 11, 663 maximum speed of a ship and increasing fuel consumption, weakening supports on oil rigs and reducing the functionality of many sensors [3]
Uncoated neoprene samples were compared to the antifouling-coated samples
The nitrile samples were submerged for two years without antifouling protection and had a large range of fouling ratings present
Summary
Fouling is the accumulation of unwanted substances, such as proteins molecules and organisms, on marine infrastructure such as pylons, boats or pipes due to exposure to their environment [1,2]. As fouling accumulates, it can have many adverse effects including increasing drag, reducing the Polymers 2019, 11, 663; doi:10.3390/polym11040663 www.mdpi.com/journal/polymers. Found that some fouling-release coatings have little or no effect on acoustic sensors, [8] but they do not clearly depict how this was ascertained. This study tries to quantify the impact of the antifouling coatings on sensor performance and the impact of fouling on sensor performance
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