Leaching Phenomena of Antifouling Agents from Ships’ Hull Paints

Abstract

Abstract:The effects of pH, dissolved ion content and relative water velocity on the release rate of an antifouling agent, cuprous oxide, from ships' hull paint have been investigated by rotating cylinder tests. Additionally, test paint panels were attached to a vessel and recovered after a certain period of voyage for the validation of the laboratory tests. In the initial period, the release rates are influenced by pH, dissolved ion content and water velocity, but once after a certain period of test, those effects become less significant. These phenomena can be explained when the paint film is fresh, the rate is controlled by chemical reaction, the surface and/or diffusion layer in the water phase governs the rate. After the antifouling substance in the paint film leached out from the near-surface region, a diffused layer (leached layer), that has little antifouling agent remained, is formed at the surface of the coating, and the diffusion in that layer can be a rate-determining process. The development of the leached layer is affected by a balance between the leaching rate of the antifouling ingredient and paint resin determined by the chemical properties and speed of the water. Thus, the leaching rates of antifouling agents are affected by the history of the paint in the water.

Modelling of discharges from Baltic Sea shipping

“…The AFP emission totals reported in this paper reflect the values obtained for the commercial fleet only, and it has been assumed that the leaching rate of the hull paint remains constant regardless of the movement of the vessel. Strictly speaking, this may underestimate the paint release rate, especially in cases where recently painted hull surface is exposed to water (Kojima et al, 2016). However, the leaching rates for surfaces which have been exposed to sea water stabilise over time and leaching rates of surfaces with paint layers older than 1 month still show some dependency on speed, but the differences are much smaller than in cases of fresh paints.…”

A Preliminary Field Study of Antifouling Paint Perfomance After Short Exposure in Mandara Bali, Indonesia

“…The thin leached layer of AF paint consist of depleted main biocide and co-biocide particles such Cu2O and ZnO [12]. In addition, in self-polishing copolymer (SPC) AF paint, the leaching release of paint commonly consist of into initial leaching and steady-state leaching releases [12,38,39]. In initial stage, leaching rate starts at once when fresh surface of paint is immersed in seawater and biocide particles begin to dissolve at the interface between the paint layer and water [38,39].…”

“…In addition, in self-polishing copolymer (SPC) AF paint, the leaching release of paint commonly consist of into initial leaching and steady-state leaching releases [12,38,39]. In initial stage, leaching rate starts at once when fresh surface of paint is immersed in seawater and biocide particles begin to dissolve at the interface between the paint layer and water [38,39]. The absence of soluble pigment biocide will leave behind pores in the matrix paint which is defined as leached layer as show in Figure 8.…”

Advanced Numerical Method for Determining the Wetted Area of Container Ships for Increased Estimation Accuracy of Copper Biocide Emissions

“…In all coatings, the aim is to achieve a controlled release of biocide molecules from the polymer matrix (so called binder), while the release mechanisms themselves differ. Although the coating release mechanisms have been elucidated and explained [10][11][12], estimates of total AF biocide emissions from cargo vessels engaged on commercial ocean-going routes are still largely based on the researchers' estimates. Observing several container vessels of various classes (designed in the period from 1990 to 2006), it is clear that the draft of vessels increases the least (given the depth limit on navigation routes and terminals), and that neither the length nor beam increases linearly.…”

“…The method does not give realistic results and has high costs. Moreover, this method was developed to measure the emission and efficacy of biocides in the laboratory, rather than real conditions of a particular location [11,35,38], while the absence of organic matter in the solution is considered a significant drawback of the method [16]. In addition, another disadvantage is that the emission results obtained by this method are significantly higher than the real emissions (compared to the results obtained by the Dome method from the same location) [19,35,39,40].…”