Barnacle Begone

Antifouling coatings have come a long way since the British put copper plate on the bottom of their wooden ships back in the 18th century, warding off barnacles and beginning nearly two centuries of naval dominance.

When ships began to be constructed out of steel, copper plating went out as it made steel corrode faster. Shipbuilders turned to copper- and tin-based coatings for antifouling including biocides like tributyltin or TBT. While TBT was effective enough to become the most common antifouling solution by the late 20th century, it was possibly too effective. Incidental TBT exposure decimated marine life and nearly wiped out oyster farms in Western Europe by the 1980s, which led to a widespread ban. The industry pivoted to copper-based coatings but ran into similar obstacles as leaching and toxicity led to environmental concerns.

Today, the coatings industry is developing the next big thing. Antifouling is an urgent priority for the world’s navies and shipping fleets. Routine cleaning of an average vessel can easily yield 200 tons of organisms, and the increased drag from a biofouled hull leads to slower speeds, millions of dollars in extra fuel costs and significantly greater CO2 emissions.

Right now, hull cleaning is still largely done manually by divers in ports wielding specialized equipment – a job that’s just as labor-intensive, time-consuming and expensive as it sounds. The dream of shipbuilders is a coating that can prevent organisms from attaching in the first place. But while that ideal is still in its early stages, some innovators are changing the game by thinking laterally. In this dawning new stage of anti-biofouling, hulls are still being scrubbed clean – just not by human hands.

Remote-Control Hull Cleaning

Norway-based coatings manufacturer Jotun has developed an elegant solution to the biofouling cycle: Instead of waiting until your ship is covered in marine life and then spending a few idle weeks or months in port getting it cleaned, why not proactively clean little by little, before the problem starts to drag performance down?

The key to its Hull Skating Solutions package is the HullSkater, a small remote-operated vehicle (ROV) that can be deployed in port or even at anchorage and crawls over a ship’s hull, spot-cleaning where needed to maintain an “always clean” hull.

The first step in the Jotun process is the application of SeaQuantum Skate, an ultra-low-friction silyl methacrylate coating that’s been engineered to work with Jotun’s HullSkater cleaning bot without eroding. The application of this coating is supervised by a Jotun project manager, who also installs the HullSkater on board and works with one of the crew members as the shipboard liaison.

Once the ship leaves port, Jotun remotely monitors the ship’s local weather and water conditions, and “big data and advanced algorithms are used to predict the probability of fouling.” If the Jotun fouling prediction algorithm concludes that the ship may need a cleaning, Jotun contacts their onboard liaison, and a session is scheduled.

The Jotun HullSkater ROV is about the size of a small vending machine and weighs around 440 pounds. Connected to the operating hub by an “umbilical cable,” it’s equipped with lights, multiple high-definition camera feeds, an acoustic node and a revolving cylindrical brush that’s similar to what you’d find in the bottom of a vacuum cleaner. Once it’s rolled down its deployment ramp, it attaches itself to the ship’s hull via four independently-motorized magnetic wheels.

The HullSkater ROV is controlled by a Jotun operator over a 4G connection. Once deployed, it creeps along the ship’s sides and bottom, looking for early signs of fouling. Biofouling actually happens in two phases. Microfouling happens within hours of entry into water and involves the formation of slimes or biofilms. Macrofouling happens more slowly as multicellular organisms like larvae, algal spores or seaweed colonize the slime.

Any of these early biofilms or bacterial concentrations discovered by the HullSkater can be scrubbed clean on the spot – before serious fouling sets in. Cleaning sessions take from two to eight hours, and Jotun’s 24/7 support means they can be scheduled around a ship’s priorities.

According to Jotun, an average bulk carrier using Jotun’s Hull Skating Solutions system will save $2.8 million in fuel costs and emit 12.5 percent fewer CO2 emissions over a five-year period. There’s also dramatically reduced risk of spreading invasive species between ports. It could be especially helpful for vessels that sail between different environments and water temperatures, which can lead to faster biofouling and more transfer of invasive organisms.

Jotun estimates that if all of these “long haul” ships used its proactive cleaning system to prevent serious biofouling and keep performance high, CO2 emissions from the industry could be decreased by more than 40 million tons a year.

Fully Automated Hull Cleaning

Armach Robotics was only incorporated last November, but it’s already rolling out an AI-assisted cleaning vehicle that doesn’t require any human guidance at all. If the Jotun HullSkater is a vacuum cleaner that you push across your living room floor, the Armach bot is a Roomba that cleans your floors while you’re at work.

“The system we have devised represents the closest any company has got to fully autonomous hull cleaning,” says Rob Howard, Vice President of Growth & Strategy.

Armach was spun off from Greensea, a company founded in 2006 to develop a software architecture for ROVs and AUVs (autonomous underwater vehicles). In 2018, Greensea collaborated with the U.S. Office of Naval Research on a project called Code 332, which called for designing an ultra-accurate navigation and guidance system for a hull-cleaning robot. Armach is the private-sector result of that partnership.

Armach’s robot is a lot different than Jotun’s: At 65 pounds, it’s much smaller and lighter, and it uses non-magnetic caterpillar tracks so it can move on non-steel hulls. It’s also completely independent, using Greensea’s navigation software to move around the hull with maximum efficiency. Because it’s man-portable, it can be rolled out simply and easily – and often.

“Currently, vessel owners are cleaning their ships once or twice a year,” says Howard. “We’ve come up with a robotic solution to clean ship hulls once or twice a month to get optimal efficiency.”

Rolling out the Armach cleaning bot every couple weeks means it only ever has to deal with microfouling – slime, biofilms, etc. – instead of advanced macrofouling like hardened barnacles. It also means the ship can perpetually operate near maximum efficiency.

Crucially, the Armach bot doesn’t have to be paired with any specific coating. “We're coating agnostic,” says Howard. “We work with the coating system on the ship.”

Another major selling point of the Armach bot is that it’s so adaptable. In fact, for shipowners under time constraints, Armach can deploy multiple cleaning bots. “We can scale the number of robots to address the needs of the operator,” Howard says. “If there’s a very short window to get it cleaned, we can use multiple units to get it done.”

A swarm of autonomous smart robots cleaning a ship while the humans sit back and watch may sound like the absolute leading edge of antifouling innovation, but things get even weirder.

A Pharmaceutical Solution to Biofouling?

There’s exciting work being done in coatings, too. Conventional coatings work by poisoning marine life before it can attach itself to the ship or by making the ship’s hull so slick that marine life slides right off when the vessel hits a certain speed. But what if there were a coating that scared organisms away from the ship without harming them?

It might sound like science fiction, but that’s exactly what a new pharmaceutical coating additive called Selektope does. Owned and developed by Swedish biotech company I-Tech, Selektope is an organic, non-metallic molecule, so it’s perfect for our era of sustainability. It’s not quite a biocide – it’s more of a biorepellent, and it works by stimulating a certain receptor in marine larvae. When the larvae draw near and are dosed with Selektope, they become hyperactive and swim away. When they leave the area of exposure, the effects disappear, and the larvae are left unharmed.

It’s a novel solution to biofouling and a highly successful one. In November 2015, a 183-meter chemical/oil tanker named the Calypso was treated with a copper-free, Selektope-based coating. For the next 63 months, it circled the globe, moving through many high-risk areas for biofouling and even lying in anchor for long periods. After more than five years at sea, the Calypso was inspected in dry dock, and zero barnacle growth was observed. A later analysis found that the Calypso’s average yearly speed loss was, incredibly, a mere 0.5 percent!

A Selektope experiment in Tokyo Bay was more modest but just as impressive. A small area of a low-activity tanker was treated with a Selektope-based coating and then left to work in Tokyo Bay, which is known as an area of extremely high biofouling. After a year, the entire hull was covered in dense growth – except for the area which had been treated with Selektope.

This experiment not only confirms that Selektope works but that it demonstrates very little seepage, limiting its effects to its immediate area. This is very important when you consider that past antifouling coatings like tin and copper were banned because they shed indiscriminately.

Winning the War

All indications suggest we’re at the beginning of a phase of intense antifouling innovation. Besides robots and pharmaceutical coatings, scientists are working on projects like micro-barbed coatings based on sharkskin and advanced polymer hydrogels that create a waterlike protective layer next to the hull, among many other innovations.

The barnacle may have been evolving for 300 million years, but in this war the smart money is on humanity. 

Thomas O'Shaughnessy is a St. Louis-based writer who specializes in helping engineers, contractors, facility managers and fleet managers understand the right industrial coating solutions for their assets.