Natural-Based Paint Exhibits Antifouling Properties
A research team from the Shenzhen Institute of Advanced Technology of Chinese Academy of Sciences and Xiamen University recently announced the results of its study of a natural-based coating, which reportedly exhibited effective antifouling and lower toxicity.
The results have since been published in International Biodeterioration & Biodegradation.
According to the release, biofouling, especially in long-term in situ monitoring, is a common challenge for underwater sensors in marine environments. Biofouling can shorten operating lifetime, increase the cost and frequency of maintenance and result in signal drift and data errors.
To find an effective method to control fouling, the research team looked to a natural product with antifouling properties, camptothecin (CPT), as an environmentally friendly antifoulant. Rather than completing lab tests, researchers utilized a more real-world method in a sea trial.
Tested panels were made from six different materials, typically used for constructing underwater sensor housing. These included three metals and three plastics, respectively:
In July 2019, the panels were partially coated with the CPT-based paint and hung under a floating raft in Xiamen Bay, China, for nine months. The panels were submerged at a depth of one meter (3.3 feet).
After the nine months of submersion, the university reports that the CPT-based paint reduced biofouling by 73.33%-96.41% compared to the control unpainted areas (100% coverage). The team noted that the antifouling of plastic was better than of the metal materials.
Additionally, researchers deployed three underwater sensors under a moored surface buoy platform in Daya Bay, Shenzhen, China, in June 2020. The sensors reportedly remained clean after four months of deployment in the marine environment.
“Our results suggest that the CPT-based paint could be used as a potential solution to control the biofouling of sensor housings for long-term in situ applications in marine environments,”said professor FENG Danqing, one of the corresponding authors of this study.
“It is worth noting that the CPT-based paint also has great potential for other artificial submerged structures in the marine environment, such as ship hulls, oil platforms and aquaculture facilities,”added professor LI Jianping, who was the co-corresponding author of this paper.
Recent Antifouling Research
Late last year, a study conducted by Egypt’s National Institute of Oceanography and Fisheries utilized algae to create environmentally friendly, antifouling marine paints.
For the study, researchers utilized extracts from four different Egyptian marine macroalgae: Ulva fasciata, Cymodocea nodosa, Padina pavonia and Colpomenia sinusa.
The water soluble polysaccharides (WSP), proteins and lipids were combined with paint into sixteen compositions, aiming to act as a biocide to create environmentally safe, antifouling marine paints. Each type of these algal extracts was mixed solely by 2% (w/w) for WSP and protein and 1% (w/w) for lipid with the prepared paint formulation.
These paints were applied to unprimed steel panels, hung on a steel frame alongside a control and submerged in the Eastern Harbour of Alexandria, Egypt. Researchers collected sea water samples to analyze during assessment, as well as visually inspected and photographed the panels.
After 171 days of immersion, results showed:
The best results were with panels coated with the formulations containing WSP. Researchers also report that the measured hydrographical parameters were within the normal range indicating that the paint compositions are environmentally safe.
In January, researchers at the University of Toronto announced they are looking at the adhesion of mussels on surfaces to potentially create new antifouling coatings for infrastructure and medical adhesives. The study, led by Professor Eli Sone, was published in Scientific Reports.
The research team has reportedly been studying zebra and quagga mussels for years at the university’s material science and engineering research lab. These species are native to lakes and rivers in southern Russia and Ukraine, and likely made their way to the Great Lakes in North America in the 80s on ships from Europe.
Since these mussel species can be invasive and cause problems, like displacing native mussel species and fouling boats, water intake pipes and other infrastructure, the team decided to look at new techniques for measuring adhesion of zebra and quagga mussels to various surfaces to develop effective antifouling surfaces.
The team utilized a pair of fine-tipped, self-closing tweezers, a digital camera and a force gauge to measure how much force was required to break the protein-based glue secreted by the mussels. The mussels were collected from the wild and placed on glass, PVC and PDMS substrates to reattach.
Quagga mussels reportedly showed a significantly lower attachment rate on PDMS compared to glass and PVC, while the zebra mussels showed a consistent attachment rate across all three substrates.
Research found that overall the mussels adhered more strongly to glass than they did to plastics. According to the University of Toronto, researchers expected this since glass is inorganic and hydrophilic, similar to the rocks that the mussels use as substrates in nature, while PDMS repels water and is often coated on boat hulls to prevent biofouling.