ABSTRACT

Corrosion monitoring of submerged surfaces is a challenging task at best. Besides being underwater, these surfaces are often covered in biofouling, preventing simple visual inspection. The biofouling itself, and the removal of the biofouling can damage the protective coatings, increasing the risk of corrosion. This paper will explore how a small autonomous robot can be used to proactively remove early-stage biofouling from a surface, ensuring the coating system remains intact, while simultaneously providing valuable visual inspection data. The paper will include results from the proactive cleaning of multiple vessels, as well as the long-term cleaning of test fixtures in high fouling pressure environments, as well as discuss the multiple benefits of maintaining a clean surface across different applications. Further, the paper will provide an overview of the technology enabling the autonomous capabilities as well as introduce potential future avenues for expansion of the technology throughout the subsea market.

INTRODUCTION

Prevention of corrosion on submerged surfaces, particularly ship's hulls, is a challenging process. Beyond the corrosive effects of seawater, biofouling will start to accumulate, and if left unchecked, can potentially damage the coating reducing its anti-corrosive properties. In stationery applications, the biofouling may be of little immediate significance, but in the case of vessels, biofouling will greatly increase hull resistance, leading to reduced speed, greater fuel consumption and emissions, as well as enabling the transfer of alien species as the vessels travel the globe.

While the impacts of biofouling predate steel ships and their associated corrosion issues, the approaches to dealing with biofouling have only recently begun to change. For hundreds of years, accumulated growth has been scraped off once its impacts became too great to ignore. Biocides have been used, and are still in use, to kill the growth before it becomes too severe, however the environmental implications of these biocides are significant and many chemicals have been banned, and others restricted in their concentration. The traditional mechanical scraping and brushing methods were damaging to the paint, and if done in water, resulted in the introduction of toxins, metals and microplastics into the water. Modern advances have improved the methods for "scraping" the hull to remove the fouling reducing coating damage, introduced systems that capture the material remove from the hull and developed coatings that cause fouling to be released from (fall off) the hull when the vessel is underway.

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