Heather Hughes – Team Leader, Non-Metallics and Coatings, explores the fundamental role that paint coatings play in ensuring that vessels remain seaworthy and performant.
For as long as humans have been venturing onto the seas, we’ve been taking action to protect our vessels against the effects of prolonged exposure to water. Vessel coatings can have an impact on everything from fuel efficiency and environmental safety through to structural integrity and more.The Greeks used hot wax to protect boats against the elements*, the Vikings industrialised the production of tar in order to coat their timbers**, and as early as the mid-1700s, shipbuilders began applying copper plating as a means to reduce the build-up of barnacles and weeds***.
Today, of course, the substance used to achieve all this, and more, is paint. It’s used for everything from aesthetics to protection, and for special requirements such as anti-slip decks and flame-retardant barriers. And paint goes far beyond just visual presentation – the right paint can actually reduce fuel consumption, cut emissions, and even reduce the amount of steel required during construction.
The paints used on vessels now are highly complex chemical mixtures, built on decades of evolution. Their composition is based on resins or binders, and includes pigments for colour and aesthetics, fillers and extenders that bulk it out, and solvents and diluents used to optimise application viscosity and/or reactivity. A range of specialist additives in marine-specific paint can aid with everything from avoiding corrosion to the absorption of UV light.
Over the past 20 years, and due to a growing number of tragedies and environmental incidents relating to vessel integrity, the International Maritime Organization (IMO) has taken a key role in determining the minimum requirements for vessel coatings
Key areas for coatings
Owner/operators are now required to adhere to either Classification Society Rules or IMO resolutions with regard to coatings across a number of key areas. Coatings of seawater ballast tanks, cargo oil tanks, and underwater hulls are all subject to governance by the IMO. Weldable pre-fabrication primers and – again – underwater hull coatings require Classification Society approval.
Underwater hulls have become a particular point of focus with regard to anti-fouling paints, which deter sealife such as shell (animal) and plant fouling from clinging to a hull and slowing a vessel down. After it was discovered that tributylin, used in a large number of anti-fouling paints, caused deformations in oysters and gender changes in whelks, legislation was introduced to outlaw the use of that chemical and other similarly harmful agents.
The monitoring of the effects of biocidal additives in the marine environment is ongoing and toughening regulation has resulted in a growing market for non-biocidal types of antifouling coatings.
Underwater hulls also require the use of high resistance paints and, in polar regions, abrasion resistant ice coatings. In this latter category, an efficient coating can actually reduce the amount of additional steel plating required from as much as 7mm to just 3.5mm enabling major savings on both fuel and fabrication costs.
Another area subject to the Classification Rules Requirements is that of weldable pre-fabrication primers. Here, the application of incorrect primers during pre-fabrication can cause porosity during the welding process. Extensive testing is required to ensure that any primer used will not impact structural integrity during the weld.
The benefits of a proactive approach to paint
Amongst the many issues that owner/operators need to stay abreast of, the condition of the paint that adorns their vessels may not be particularly high on the list. Nonetheless, a forward-thinking approach to coatings can pay dividends with very little extra work required.
From a risk prevention point of view, understanding the condition of your paintwork can help to reduce the danger of both catastrophic failure (such as the integrity of a cargo oil tank) and spiralling cost inefficiencies. Anti-fouling paint plays a major role in enabling a vessel to sail unhindered, optimising fuel consumption and expenditure as a result.
Naturally, preventing failures of this kind also helps to ensure that vessels do not need to dry dock earlier than their scheduled five-year interval. And, even when that return does come due, a well-treated vessel is likely to be able to return to active service much faster than one requiring significant recoating following its required paint inspections.
Put simply, a proactive approach to coatings can save owner/operators money, minimise the need for maintenance and repair, and reduce lost productivity from dry docked vessels.
With a wealth of experience in everything from coating formulation, testing and survey, to type approvals, our expert Marine Coatings team is always on hand to help you understand the right approach for your fleet.
* Marine Fouling and its Prevention – US Naval Institute, 1952
** Vikings conquered treacherous seas and created a formidable navy thanks to mass-production of tar which was used to waterproof their ships – The Daily Mail, 27th December 2018
*** Copper Hull Sheathing Foils Barnacles – Copper Development Association, Inc.