Corrosion passivation of ballast water tanks by means of floating.

A corrosion passivator interrupts the connection between metal and corrosion. By forming electron pairs, particles enter into a chemical bond with the host metal behind the corrosion. This bond makes the metal immune to corrosion influences such as heat, moisture, salt and oxygen.

Corrosion passivation is possible without the need for blasting or sanding. A dry surface is not required. Depending on conditions, the metal remains protected from corrosion for 6 to more than 25 years.

 This technology is incorporated in fluids, primers, epoxies and other types of coatings and is slowly entering the market for inland- and ocean-going vessels since 2010.

For instance nC Corrosion Passivator Fluid is formulated in a carrier that is lighter than water. This makes it possible to come to a 100% coverage of the metal structure without spending much time and money on scaffolding and prepwork. By dividing the corrosion passivating fluid over the tank’s floor and then followed by just filling and emptying the tank (or any other confined structure) with water, the nC Corrosion Passivator Fluid will be lifted up by the water and divide itself over the metal surface.

 Here is a pictured breakdown of the project steps of this amazingly easy form of corrosion protection:

Step1. Equipment

In order to fill and empty the tank, one can rely on pumping system on board, but always have 2 submersible pumps with you to stay agile in case extra pumpvolume is required, or valves or parts of the tank cannot be reached.

Furthermore, a pressure vessel in combination with an aircompressor could be helpful to passivate parts of the tank top by means of spraying. To avoid that the water level does not reach the tank top because the vessel is not perfectly horizontal, or in the case of trapped air at the tank top, spraying is the safest way to go. When there are ventilation-shafts present, you can of course fill the tanks to the brim.

Wear the obvious safety clothing like safety boots, helmet, mouth-mask, gloves, and have a strong light at hand to inspect coverage afterwards.

Step 2. Inspect and Measure the tank.

Measuring all tanks, in case the tank plan has changed or if there just isn’t any. On every 1m³ of tank volume, pour in 0,8 up to 1,2 liters of nC Corrosion Passivator Fluid in the tank. It is safe to say that most ballastwatertanks need 1 liter fluid per 1m³ tankvolume.

Step 3. Spray the tanktops if necessary.

Treating the tank tops first may be necessary. Do this before you spread the corrosion passivating fluid over the tank floor. You can also do it after filling and emptying the tank, the missed spots are easy to find. nC Corrosion Passivator Fluid contains no solvents or metals and is safe to work with, so there are no issues with regards to dizziness, fumes and gases.

Step 4. Divide the nC Corrosion Passivator Fluid over the tank floor.

Although not necessary per sé, spreading the corrosion passivating fluid over the floor gives an instant better spread of the passivating fluid on the water surface once pumping has started. Make sure all small flush holes in the web-frame are open.

Step 5. Fill the tank with water.

You can use fresh or salt water. Make sure that the rising pace of the water does not exceed 20 cm/min. Also make sure that the end of the hose stays low, deep under the rising water surface. This creates a useful current and enables the fluid to separate from the water and stay on top.

Step 6. Wait 15 minutes when at the tank top.

When the waterlevel reaches the tank top, a lot of air will escape. Allow the water to stay in contact with the tank top for at least 15 minutes so that the top gets saturated and the trapped air will come out.

Step 7. Empty the tank

Take the pump out of the water and place it in the ballastwatertank. Then pump the water overboard or use it to fill another tank to move on with the passivating sequence. Remember, if you pump the water from tank to tank, each INDIVIDUAL tank needs to have their tanktops sprayed and each individual tank needs to have its own calculated amount of passivator already on the tank floor. 

Step 8. Inspect the tank.

Corroded metal that has been in touch with nC Corrosion Passivator turns anthracite or deep purple in color. Now you see if and where a spot is missed!

Step 9. Clean up.

When finished, clean up all gear, clean up the area. nC Corrosion Passivator Fluid has woolfat as a carrier, this is what you do NOT want on deck and on your equipment. And go to back to the office and report the job done!

If you want more information about corrosion passivation, you can download our brochure https://www.nc-protect.com/brochures/Brochure_Corrosion-Passivator_ENG.pdf

Or check out our application video: https://www.youtube.com/watch?v=EXm_OkrSZdI