Tanks in conflict
Concerns are rising that rulings to safeguard against ballast water tank corrosion could be rendered useless if the ballast water treatment system isn’t carefully considered. Solutions looks at how this potential for problems has arisen
IMO’s December 2006 approval of a Performance Standard for Protective Coatings (PSPC) for water ballast tanks and the earlier International Convention for the Control and Management of Ships Ballast Water & Sediments (SBWS) is generating concern over a potential for conflict between them.
The two pieces of legislation could have implications for the ship repair and newbuilding sectors because of PSPC’s focus on surface preparation, coating application and their subsequent inspection and planned maintenance throughout a vessel’s life and the impact of the ballast water treatment system installed on the coating system applied.
Potential for conflict
Essentially, the aim of PSPC is to improve ship safety by ensuring that the coating applied to ships’ ballast tanks at the newbuilding stage will last for at least 15 years. Under SBWS owners need to take adequate measures to ensure that alien species migration is properly controlled and minimised. There are several proposed solutions for this, but some of them will change the environment in the ballast tank.
“What is interesting is that the two regulations make no reference to each other and could cause serious problems for IMO and regulators. There is a real potential for conflict here,” says Raouf Kattan, managing director of coatings consultancy Safinah.
Having selected an approved paint, the shipowner has then to decide which type-approved ballast water treatment system to install. But, as Kattan notes, most ballast water treatments being developed are categorised as “active substance” systems – ie they use chemical additives or induce chemical changes to the ballast water characteristics – and could damage the coating. The potential to damage the coating or aggravate corrosion varies considerably from system to system.
Ole Borring Soerensen, chief consultant at Hempel’s Centre for Applied Coatings Technology, tells Solutions that only those ballast water treatment systems that use aggressive chemicals, particularly chlorine, will damage protective coatings.
Although most chlorine-based treatments have a chlorine content of less than 1ppm, if the concentration is increased it will “pose a significant and rapid threat to the longevity of the coating” – in days not years!
Compatibility
Hempel’s Jørn Kahle believes that if the ballast water treatment system is a “killer coat” system then due consideration should be taken when selecting the protective coating. Yet Safinah understands that only one company has carried out extensive testing on the impact of its water ballast treatment system on tank coatings and on corrosion in the tanks in general.
Kattan puts forward a case for placing responsibility in the hands of the relevant parties, but acknowledges potential ambiguities.
“The designer/shipyard could ensure that the systems selected are compatible, but where are they to get the data from? It could be the responsibility of the paint company to ensure that all systems are compatible with all their recommended schemes at newbuild, but what happens if the owner changes paint supplier later? It could be the responsibility of the treatment equipment supplier to assure compatibility with all paint company materials, but this would be a long and drawn-out testing process with a considerable number of schemes and products to assess.
“[These ambiguities need] to be addressed and responsibility placed firmly with one party or another. There is a need therefore to co-ordinate to ensure that either the supplier of the ballast water treatment system of the paint company, or the shipyard or the owner ensure that the two systems (coating and treatment) are compatible,” says Kattan.
Cost increment
Implementing the coatings’ performance standard also has financial implications, which will undoubtedly place a premium (perhaps as much as 10%) on the cost of a newbuild. In part, this is due to the increase in inspections/audits which will lead to identification of more failures and hence an increased workload at the shipyard.
If 10% more effort is required to surface-prepare, paint and inspect them, then output from the yard will decrease by 10%. To recoup this lost turnover the yards are expected to charge more per ship to maintain their levels of performance. Coatings manufacturers will also incur additional costs because of the increased documentation required to meet the regulation and it is likely these will be pushed on to the customer.
“If the amendments have the desired effect of reducing failures in ballast tanks, then repair yards may expect a drop in the demand for future ballast tank coating work, starting in about five years. This may not only affect the repair yards but also those companies specialising in onboard maintenance using riding crew,” Kattan says in a Gard News article.
If the amendments fail to have the desired effect, however, ballast tanks could be subject to more frequent class inspections, raising the demand for coating work for the repair yard. It is also possible that coating solutions would be limited to those approved by the PSPC, which may hit some of the smaller paint suppliers, suggests Kattan.
The amount of work to be carried out will of course depend on the assessment of the degree of failure – a notoriously difficult evaluation to make. Studies carried out by Safinah, supported by work carried out by Muehlhan Surface Preparation, show that assessment by different inspectors – even among those who are well-qualified and experienced – can lead to discrepancies of up to 400% in the assessed percentage of rust-spotting. Attempts are being made to develop more objective assessment methods.
Kattan asks what will happen at the end of 15 years. “If by then the coating has reached the end of its useful life, then repairers could expect an increase in demand for ballast tank coating work and the challenge will be to develop the technologies to handle the work economically and efficiently within an ever-tightening environmental framework.