Nano Corrosion Passivation: Here to stay?

By Rob van Hoorn
CCO at NTA Maritime

“Can you develop a technique that will stop the corrosion process without sandblasting or coating?” Bart Otto, CEO of Flinter, formulated this challenge back in 2012. The Dutch shipping company was looking for cost-effective methods to stop corrosion within their vessels, without losing time on (sand)blasting, cure time or drydocking.

Dutch-based NTA Maritime got to work. Their know-how of metal passivation, chelation and bonding of nanoparticles led to a corrosion passivation technique that can: 1) save cracked hard coatings from further damage and 2) is able to stop the corrosion process on new, uncoated or already corroded steel for up to five years. And yes, without the traditional sandblasting or spot repairs of coating as we know it.

Making it work
The new technique would have some important responsibilities. The main one is to make metal less or not at all affected by factors like air or saltwater. Undermining and avoiding enclosure of disturbing pollution by cleaning out surfaces is another. And how to treat corroded areas under existing coatings, without disturbing the mechanical bond of the already present paint or coating on sound metal areas?

It became clear that applying nanotechnology would have some significant benefits. By developing nanoparticles that interact with the iron behind the rust, NTA was able to separate the iron oxide from the surface and passivate the corrosion process. Rust is not converted into a layer or patina, it just will not affect the metal anymore. The challenge was to find a suitable binder, responsible for bonding the particles in the metal, and an efficient carrier, to transport the particles into every inch of material that needed treatment.

After a number of successful pilot projects, it became clear that the technique of passivating corrosion worked, but the method of application needed improvement. When working in confined, dark, wet and cold areas (such as ballast water tanks), you cannot expect people to deliver a perfect job. Also durability needed to be improved, to offer class-societies and ship-owners the chance to bridge the gap of five years from special to special survey. Therefore, the binders were improved and verified for longer lasting performance.

Getting the nanoparticles in place
During 2013, focus was set on developing the carrier for the active particles and its binders and make it perfectly suitable for coating of hard-to-enter internal structures of ships and platforms. The maritime experience of the team of developers turned out to be key.

Only a carrier that is capable of floating on water, with high separating capacities and without losing or hindering the active components, can bring the required 100% coverage rate. Without the need for applicators to enter the targeted spaces, floating was chosen to carry the corrosion passivator in place. Flinter appointed several vessels for a corrosion passivation treatment. Criteria for selection: No hardcoat present, recent steel renewals and ultrasonic measurement of material thickness beforehand. Dutch-based sea-going companies like Acta Marine, Abeko and Kotug along with several inland-shipping vessels and two steel wire rope producers soon joined the group of early adaptors.

Ticking the QHSE-boxes
To be widely applicable, the technique had to tick all the boxes when it comes to Quality, Health, Safety and Environment (QHSE). For quality, the technique met several corrosion tests along ISO standards, executed by certified and accredited organizations. It passed 4,350 hours of continuously dipping in fully saturated salt water without any sign of corrosion. Steel renewals at Flinter that were placed in 2012 without coating and were treated with corrosion passivator, showed no corrosion impact when inspected during 2015.

When steel internals have to be blasted and recoated, health is a big issue. It requires serious protection of vital organs as eyes, lungs and skin. Leaving the blasting out of the process, and the fact that corrosion passivator does not contain solvents, heavy metals or carcinogenic or mutagenic components, a big step is made regarding health issues in corrosion protection.

Regarding safety, corrosion passivation enables a step forward. Hard-to-enter internal structures do not have to be entered during application, because of the floating application possibilities. The fact that the product emits no Volatile Organic Compounds (VOC’s) makes that treated areas do not cause dizziness or develop explosive fumes.

Cleaning up a yard that has been busy recoating ballast water tanks, means disposal of vast amounts of coating pails and big bags of blasting medium. Cleaning the yard and the vessel itself are next. Through corrosion passivation none of that is necessary. The left-over passivator is re-usable and thereby harmless in open water. Adding up again, this time in terms of environment.

The bottom line
Looking over more than 20 projects executed so far, time consumption is cut by 70% compared to the traditional approach. “At Tuzla Shipyard we were drydocked with our vessel Flintersky,“ Flinter superintendent Job Pannekoek recalls. “We docked together with two capesize bulkers and were squeezed in between them. All three of us needed steel renewals and new ballast water tank coating. After two days of steel welding we went out on day three, to the big surprise of the fleetmanagers of the two other vessels. They didn’t believe we could blast and coat our ballast water tanks in the water. And they were right, we didn’t. We just passivated the whole lot in two more days and left everybody behind their calculators, heading for Constanta!”

The average cost of product shows 50% to 60% lower rates than the traditional approach. Absence of scaffolding also helps. Low cost and easy application offer owners the possibility to take action fast. The general condition of assets is expected to stay on higher levels, as it is less costly to maintain high standards in corrosion protection.

Here to stay
Corrosion passivation has entered the market and is looked into by class societies. It can be applied in various areas, such as in ballast water tanks, on steel wire ropes, in thermal insulating coatings or to prevent carbon build-up and scuffing inside (HFO) pipes, tubes and engine internals. Several developments are already underway, bringing new possibilities for profitable sustainability for ship owners, confirming that corrosion passivation is here to stay.

The Industry Contribution is a new section in which maritime companies share their project endeavors or analyses. Please contact us at [email protected] for inquiries.