Corrosion Passivation Hull Internals Tugboat Adriaan
Kotug is a leading towage operator offering its services to ports and terminals on a global scale. During March 2016, inland tugboat Adriaan, the oldest tug in the fleet of Kotug and one of the first tugs operated by the company back in the 50’s, docks at Padmos Yard, the Netherlands. One of the applications of choice during that docking is Nano Corrosion Passivation. This technique proves itself on board of the Adriaan since the first application of Nano Corrosion Passivator in 2011.
In need of steel renewals in several parts of the hull, the opportunity was there to stop and prevent corrosion on hard to reach places at the aft of the vessel. Still, hard to enter voids in the aft peak tank were present. Corrosion passivation fluid was the technique of choice of Kotug’s projectleader. nC Marine deliveres and applies nC Nano Corrosion Passivator Marine on the hull’s internals of inland tugboat Adriaan.
The silvery look will remain for just a couple of minutes and will turn into an anthracite or even blank steel colour, depending on the severity of the corrosion. The more corrosion present, the blacker the surface becomes.
nC Nano Corrosion Passivator
nC Nano Corrosion Passivator comes to the metal by a natural fatty ester carrier. These esters allow the active particles to nest in the metal and remain active without hinderance of a drying coating. The esters keep the active particles in place long enough to do their work of descaling and passivating. Especially in ballastwatertank environments, where (salt) water floats and flushes in and out, it is of great importance to use the right esters in order to withstand the flushing and keep the particles in place.
After several weeks, the surface becomes dry again, with the active corrosion passivating particles firmly in place. Typically, nC Nano Corrosion Passivator lasts for five years in salt water environments, like ballastwatertanks are.
In order to meet CAP or Class standards, nC provides a top finish that can be applied over the NCP treatment. The lattice structure of aluminium particles in this finish covalently bonds into the surface during the drying process. In combination with nC Nano Corrosion Passivator, the metal cleans out from enzymes, salts and minerals. It has protection by corrosion passivation AND enjoys coverage by a flexible hardcoat finish.
Visible on this picture above is the ready product nC Nano Corrosion Passivator on the left side (in the white bucket), and active corrosion passivator concentrate (in the small cans) that you add when the severity of the corrosion requires a stronger pre-mix, or, as in this case, the passivated area is very small but still needs a certain wet film thickness (WFT).
Application phase. Picture above left: Pour in the right amount of nC Nano Corrosion Passivator. Base the calculation for the correct amount on m² (surfaces, spot-repairs) and/or m³ (ballastwatertanks,voids, peaks, internal structures). Picture above middle: Pour in water. You can use sea water or freshwater, it does not matter. Please allow a maximum rise rate of 20 cm a minute (faster is possible, but we will have to adjust the concentration of the pre-mix). Make sure you reach the tanktops to the full. At nC Marine we position airhoses (click for picture here) by means of magnets at the highest point of the tank, so air can freely escape without forming air-pockets in the tank. Picture above right: So… you can do something else now!
nC Nano Corrosion Passivator requires no blasting, peeling, coating or drying. Call your wife you’ll be home early. Or tell your charterer you will be on-hire sooner than expected.
- Displaces water, requires no drying before or afterhand.
- Passivate corrosion, keep material thickness as it is for 5 years (saltwater tanks) or forever (freshwater).
- No cost or off-hire time for sandblasting, coating, curing.
You can pump everything out in a drum or IBC (unless you are certain there are no oil or other contaminants in the water, NCP itself is harmless for aquatic life), but smarter is to leave a very small amount of water/NCP mixture behind. This way you can re-use the leftover NCP. NCP will not deteriorate over time. The surface you are looking at will get dry within weeks.
Consider the next points of interest:
• NCP separates oxidation from sound metal. It undermines bigger rustflakes and they will come loose. This can lead to plugging of the suction mouth in the tank. In case of ballastwatertank: Please check if large amounts of rust are loose on the tank bottom AFTER THE FIRST JOURNEY AT SEA after the treatment is done. Check ΔP (Delta P; pressure change) of pumping system if possible.
• The corrosion passivator undermines corrosion that occurs under visible sound looking coating. This means surprise areas of corrosion can fall off. Passivation of the metal is complete, but again the risk of plugging the suction mouth occurs. Check ΔP during emptying.
• It is wise to inspect the tanks after a couple of times of ballasting, or at least after 3 months. If clear new flash rust occurs, this is a sign that the NCP is not covering completely. If the corroded areas show an uniformly greyish or anthracite trace and if the corroded areas show a brown/reddish gloom, everything is perfectly allright.
• All tanks hold a residue of NCP. This enables the tanks to “re-treat” themselves in case of welding later. Always check if new inserts start corroding around the welds. Carry out subsequent treatment by brushing.
• In case of sailing through a storm, additional rust flakes will come off. Check ΔP during pumping.
• When pumped through, NCP will descale pipes and tubes internals.
About nC Nano Corrosion Passivator Marine
nC Nano Corrosion Passivator is designed to stop the corrosion process. Material thickness will remain stationary, without the need for sandblasting, coating or other expensive and time-consuming work and materials, as NCP Marine can be applied by flushing the ballast water tanks, rudders, voids or other spaces, and if necessary by spraying or brushing. If you have a material thickness that is sufficient now, but will be subject to replacement during the next special or intermediate survey, here is your solution to keep thickness as it is right now.
The NCP fluid works through a process called chelation in which large synthetic molecules form a bond with the iron behind the rust, thereby pulling the loose iron oxide from the surface. NCP Marine forms a flexible barrier inside the capillar and intermolecular structure of the metal surface. The formulation passivates the metal corrosion process.