Ship hull in-water cleaning and its effects on fouling-control coatings

Abstract

Today, ship hull fouling is managed through fouling-control coatings, complemented with in-water cleaning. During cleaning, coating damage and wear must be avoided, for maximum coating lifetime and reduced antifoulant release. When possible, cleaning should target early stages of fouling, using minimal forces. However, such forces, and their effects on coatings, have not yet been fully quantified. In this one-year study, minimal cleaning forces were determined using a newly-designed immersed waterjet. The results show that bi-monthly/monthly cleaning, with maximum wall shear stress up to ∼1.3 kPa and jet stagnation pressure ∼0.17 MPa, did not appear to cause damage or wear on either the biocidal antifouling (AF) or the biocide-free foul-release (FR) coatings. The AF coating required bi-monthly cleanings to keep fouling to incipient slime (time-averaged results), while the FR coating had a similar fouling level even without cleaning. The reported forces may be used in matching cleaning parameters to the adhesion strength of the early stages of fouling.

Keywords:

• Adhesion strength
• ship hull fouling
• fouling control coatings
• microfouling
• calibrated waterjet
• energy efficiency

Supplemental materials

Sensitivity analysis for surface forces under an immersed vertical jet (six figures) Spreadsheet 1/2: Paint_damage_according_to_ASTM_D6990-05.xlsx Spreadsheet 2/2: Raw_data.xlsx

Acknowledgements

The authors would like to acknowledge Björn Källström (Gothenburg Marine Biological Laboratory), Rasmus Ravnsborg (Diving Unlimited, Gothenburg) and Dan Zackariasson (Chalmers) for valuable suggestions and support during the design and construction of the immersed waterjet device for adhesion-strength testing. Acknowledgements are also due to Grefab AB for kindly allowing access to their marina, Irma Yeginbayeva for assisting with ADV measurements, and Maria Lagerström and Erik Ytreberg for valuable comments on an advanced version of the manuscript. SEM-EDX analysis was performed at the Chalmers Materials Analysis Laboratory (Gothenburg, Sweden), and the authors would like to acknowledge the technical support received from Stefan Gustafsson.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was prepared within the project COMPLETE - Completing management options in the Baltic Sea region to reduce risk of invasive species introduction by shipping [#R069]. The project is co-financed by the European Union’s funding Programme Interreg Baltic Sea Region (European Regional Development Fund).