Nano Corrosion Passivation for Maritime Purposes

By Rob van Hoorn
CTO at nC Marine

What happened so far:

At the beginning of 2012, Dutch shipping companies were looking for cost effective methods to stop corrosion within their vessels, without losing time on (sand)blasting, cure time or drydocking. A team of Dutch-based chemists, nano- and corrosion specialists lead by Rob van Hoorn (nC Marine) together with shipowners, superintendents and engineers got to work. The know-how of metal passivation, chelation and chemical bonding of nanoparticles led to a corrosion passivation technique (inactivating corrosion and metal) that was put to use on several ocean-going vessels and steel wire ropes.

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 and cover the wished 15 years of service. Therefore, the binders were improved and verified for longer lasting performance.

Corrosion passivating fluid

During 2013, focus was set on developing the carrier for the active particles and its binders and make it perfectly suitable for treatment of hard-to-enter internal structures of ships and platforms. The first focus was on a carrier that is capable of floating on water, with high separating capacities and without losing or hindering the active components. This can bring the required 100% coverage rate. Without the need for sandblasters or applicators to enter the targeted spaces, floating was chosen to bring the nC Nano Corrosion Passivator, as the product is called, in place. Flinter appointed several vessels for a corrosion passivation treatment, as no hardcoat was present in the ballastwater tanks of these vessels. Also, steel renewals just have been done and ultrasonic measuring was executed. 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.

The technique proved to work. For instance, 27 months after treatment of the double-bottom tanks of the multi-cargo vessel Flintersky, the webframes showed a stable surface, without active corrosion present. During October 23rd till October 25th 2014, mv Flintersky got her complete set of 10 DB-tanks treated with nC Nano Corrosion Passivator. Project leader, Superintendent of Flinter mr. Job Pannekoek, and nC Marine’s mr. Rob van Hoorn executed the job. This process was done without sandblasting or coating, as the technique needs to passivate corrosion without the smooth shiny finish you want to see on a superstructure or coaming. Goal here was to maintain material thickness of corroded webframe as it was. Underneath pictures are taken during the period October 2014 and January 2017 Flintersky’s tank DB5PS:

Spotrepairing and welding

During 2016, the the focus shifted to a hardcoat version, as shipowners also wanted to be able to put Nano Corrosion Passivator to use on newer vessels and visible areas. Discussing the technology with shipowners and yards, it became clear that the luxury of not having to remove corrosion was very much sought after, but also there was a strong need for a coating that could withstand extreme heat.

The hardcoat version of the corrosion passivator allows spotrepairing with or without corrosion removing actions as blasting, jetting or chipping. The difference is that you need a primer coating if you leave the corrosion on the surface, ending with a layer of <35 microns at a weight of <49gr/m². You can go for one coat if you work on a clean or new surface, leaving a layer of < 15 microns at a weight of < 24gr/m².

Welding the cargo on the hold’s floor means damaged coating at the internal side, the tanktop. This leads to corrosion. Also extreme chemical resistance was sought after, as tanktops and other metal corrode fast and severely on tankers of all kinds.

The good thing about nanotechnology is that it forms a chemical bonded matrix, or cold alloy, inside the metal surface. This chemical bonding outperforms the traditional mechanical sticking of today’s coatings both in lifetime cycle as well as protection. The process of bonding takes place when air, water and elevated temperature is present. Depending on the nanoparticles, a matrix can withstand temperatures up to 1,500 degrees Celsius/2,730 degrees Fahrenheit. At these levels, the carrier that puts the particles in place is long gone, but no harm done, as the particles irrevocably bond in less than 24 hours, to come to full strength after 5 to 7 days. So, with the new feature, nC Nano Corrosion Passivator keeps on protecting our metals even after welding has been done. The bonded layer, or cold alloy, is extremely shear and shock-load proof. Basically only a rupture can damage the cold alloy. Verification tests show lifetimecycles of > 15 years so far for the hardcoat version of the corrosion passivator.

Application of the nC Nano Corrosion Passivator hardcoat is done by means of brush, roller or airgun. The surface may be wet, but standing water must be avoided, as well as washing water. No special equipment is needed.

Here to stay

Corrosion passivation has entered the market and is looked into by class societies. It can be applied in various areas as long as metal is present. The development of the hardcoat variation brings new possibilities for profitable sustainability for ship owners, again confirming that corrosion passivation is here to stay.

Note: The opinions, beliefs, and viewpoints expressed in this article do not necessarily reflect the opinions of World Maritime News.