Quantification of paint flakes and metal emissions during pro-active in-water hull cleaning

Pro-active in-water hull cleaning is a viable option for reducing greenhouse gas emissions and preventing the transportation of non-indigenous species. Conversely, pro-active in-water cleaning (IWC) might lead to the emission of antifouling paint particles and biocides, posing a risk to the marine environment. However, the analysis of these APPs is particularly challenging. We have therefore adapted a thermoanalytical approach using pyrolysis-gas chromatography/mass spectrometry to analyze the abrasion of APPs. In this approach, the mass of APPs is determined by analyzing the polymer backbone and external calibration. We investigated the particulate abrasion of antifouling coatings for one ship with a self-polishing coating, one with a foul-release coating and one with an abrasion-resistant coating, in order to evaluate the different abrasion behavior and the suitability of the respective coating types for pro-active IWC. In addition, the zinc and copper emissions were analyzed.

The extrapolation of the abrasion for ships with 10,000 m² of wetted surface shows that both the abrasion-resistant coating and the foul-release coating release only small quantities of APPs during IWC, with 1.2–2.1∗10⁻⁴ kg for the abrasion-resistant coating and 0.015 kg for the foul-release coating. The potential emissions for self-polishing coatings showed significantly higher abrasion with 1.9–4.3 kg. In addition, copper and zinc emissions showed the same distribution trends for the self-polishing coating samples and were between 2.2-9.5 and 1.1–3.2 mg/L, respectively, exceeding common water quality standards by far. These results demonstrate that caution is required when balancing the advantages and disadvantages of IWC, especially with regard to self-polishing coatings.