Trends in the development of environmentally friendly fouling-resistant marine coatings

Abstract

'marine biofouling', the undesired growth of marine organisms such as microorganisms, barnacles and seaweeds on submerged surfaces, is a global problem for maritime industries, with both economic and environmental penalties. the primary strategy for combating marine fouling is to use biocide-containing paints, but environmental concerns and legislation are driving science and technology towards non-biocidal solutions based solely on physico-chemical and materials properties of coatings. advances in nanotechnology and polymer science, and the development of novel surface designs 'bioinspired' by nature, are expected to have a significant impact on the development of a new generation of environmentally friendly marine coatings. Marine biofouling, the colonization of submerged surfaces by unwanted marine organisms ( Fig. 1), has detrimental effects on shipping and leisure vessels, heat exchangers, oceanographic sensors and aquaculture systems. For example, it has been shown that the increased roughness presented by a heavily fouled ship hull can result in powering penalties of up to 86% at cruising speed; even relatively light fouling by diatom 'slimes' can generate a 10-16% penalty 1 . Without effective antifouling (AF) measures, in order to maintain speed, fuel consumption (and therefore greenhouse gas emissions 2 ) increase significantly. A recent analysis of the economic impact of biofouling for the Arleigh Burke DDG-51 destroyers, which comprise 30% of the ships in the US Navy fleet, estimates the overall cost associated with hull fouling at $56 million per annum 3 . This figure is based on the present AF coating system, cleaning and fouling level (typically heavy slime) of the Navy. If the analysis is extended to the entire US Navy fleet, the approximate cost of hull fouling is between $180 and 260 million per annum.Marine biofouling is ubiquitous and has been a practical problem ever since man sailed the oceans; controlling it, without simultaneously creating unacceptable environmental impacts on non-target species is a considerable challenge. Recent years have seen a resurgence of interest in the fundamental science behind the processes involved in biofouling, and in the design of novel coatings and other non-coating technologies. The main driver for this is legislation that has outlawed some highly effective AF paints, notably the use of tributyltin oxide, and posed a stricter evaluation and regulatory regime on the use of alternative biocides. 'Green' alternatives to biocide-based technologies are therefore urgently sought by the marine coatings industry, and there is considerable interest in developing biocide-free coatings that rely on surface physico-chemical and bulk materials properties to either deter organisms from attaching in the first place ('prevention is better than cure') or reduce the adhesion strength of those that do attach, so that they are easily removed by the shear forces generated by ship movement or mild mechanical cleaning devices.

Surface Sensing and Settlement Strategies of Marine Biofouling Organisms

“…Fouling pressure in the ocean is high as adhesion is a central stage in the life cycle of many micro-and macrofoulers [13,14]. Three different approaches are commonly pursued against marine biofouling: toxic anti-fouling, fouling-inhibiting and foulingrelease coatings (schematically depicted in Fig.…”

“…Many of such biofouling laboratory assays focus on the sessile spore or larvae stage rather than the adult, macroscopically visible biofouling organism [14,[48][49][50]. In general, the applied assays can be subdivided into biomass accumulation measurements (settlement assays), adhesion strength measurements, and tracking experiments to quantify exploration behavior.…”

Charged hydrophilic polymer brushes and their relevance for understanding marine biofouling

“…The presence of biofilms on surfaces may influence the settlement of propagules of higher organisms such as algal spores (Joint et al 2002, Marshall et al 2006, Mieszkin et al 2013, Patel et al 2003, larvae of barnacles (Dobretsov et al 2013, Hadfield & Paul 2001 and tubeworms (Hadfield 2011, Zardus et al 2008. The colonization by these organisms on surfaces leads to economic and environmental costs, which have been widely reported (Callow & Callow 2011, Fitridge et al 2012, Schultz et al 2011). …”

Nanospherical arabinogalactan proteins are a key component of the high-strength adhesive secreted by English ivy

“…ivy nanoparticle | ivy adhesive | arabinogalactan protein | adhesion mechanism | reconstructed adhesive A lthough there is a growing interest in exploring mechanisms regulating a variety of adhesive behaviors in the animal kingdom (1)(2)(3)(4)(5)(6), the molecular basis allowing creeping plants, such as English ivy (Hedera helix), to generate sufficient adhesive force, aiding in clinging to vertical surfaces, is rarely discussed (Fig. 1A).…”