Paints and coatings play an essential role in shipping far beyond the obvious one of aesthetics. Maintaining ships in a condition suited to their employment involves a constant battle above and below the waterline with the twin enemies of corrosion and fouling.
Corrosion is an inevitable factor for all ships as ferrous metals all have a tendency to chemically react to revert to their natural state as iron oxide. The process of turning raw iron ore into steel is an expensive one but preventing reversion is just as costly for the owner.
Externally corrosion, reflects badly upon the ship, its crew and its owner and can provide the reason for Port State Control officials to take an interest in the ship that may well throw up other shortcomings. Internally protection is also needed, and in some very inhospitable areas.
The cargo holds of a bulk carrier can suffer badly from both corrosion and physical damage caused by the nature of cargo and loading and discharging operations. Protection against corrosion is also vital in ballast tanks, void spaces and the cargo tanks of crude and chemical tankers.
Hull fouling is one of the biggest hurdles to overcome in maintaining a ship’s efficiency and thus the degree of success will determine both the fuel bill and the amount of emissions the ship produces. It will therefore impact on the owner’s bottom line and has the potential to keep the ship within the legal limits imposed by MARPOL and other national and regional regulation.
Until very recently shipowners were more or less free to decide what parts of a ship were coated and with what. But that is changing, and although rusty ships will almost certainly be around for many years to come – and most probably forever – some areas of a ship’s structure are already subject to mandatory coating and to definitive standards under both IMO regulations and the IACS common structural rules. Things are also shaping up for regulations to be drawn up compelling owners to not only apply anti-fouling or foul release coats but to ensure that they remain in good condition regardless of when the next scheduled drydocking is due to take place.
Coatings are not the only tool in the fight against corrosion. Cathodic protection, chemicals and even the choice of materials are also employed to prevent a ship and its equipment from the inevitable return to iron oxide which is the natural state of the main metal used in ship construction. One day, non-corroding materials may replace steel but while there is progress it is still a long way off and the battle must go on.