Mandatory coatings, their application and maintenance are not yet things that operators need to worry about but as from the 1 January 2013 ships have been required to implement a Ship Energy Efficiency Management Plan (SEEMP). Under IMO regulations the exact date for individual ships is the first intermediate or renewal survey after 1 January 2013 and so with a very few exceptions most ships should now have a SEEMP in place.
Since hull fouling has an obvious detrimental effect on a ship’s efficiency it is evident that the matter of anti-fouling should be covered in its SEEMP. Taking voluntary action on biofouling is something that many operators do as a matter of course could but formalising procedures could make a ship more attractive to potential charterers and an obvious concern for environmental matters is likely to influence official inspectors in a positive way.
The various claims made by makers of hull coatings with regard to performance and fuel saving potential have long been treated with some jaundiced suspicion by operators and with no universal method for measuring the savings achieved this is understandable.
However the development of ISO 19030 as a new standard for Measurement of changes in hull and propeller performance is considered a major step forward. This standard complements ISO 15016 (for sea trials) focussing on in-service monitoring. ISO 19030 uses a 3-tiered approach, reflecting different levels of accuracy. At the lowest tier, noon reports are used, at the highest tier, continuous monitoring systems with automatic data collection. In September all three parts of the standard were at the final stages of approval by the ISO secretariat and barring any late snags should become effective in the closing weeks of 2016.
Every shipowner should know that ballast tanks have historically proven a troublesome part of the ship to maintain and also that any failure in their structure can have catastrophic results. Any movement of the ship can start a scouring process inside the tank by the sand and sediments taken in during ballasting. Cleaning and coating of tanks was most often carried out more to meet cost and time limits rather than to a high standard. Inspection of ballast tanks during construction, repair and in service was also often a cursory process and the standard of training sometimes such that difficult to spot deficiencies were overlooked.
As work at the IMO on the 2004 ballast water treatment convention was coming to a close attention there, and in IACS, turned to addressing the issues of ballast tank coatings. In 2006 at MSC82 the IMO adopted Resolution MSC.215(82) Performance standard for protective coatings of dedicated seawater ballast tanks on all new ships and of double-side skin spaces of bulk carriers, which was made mandatory by way of amendments to SOLAS regulations II-1/3-2, also adopted at the session.
The amendments subsequently entered force in 2008 and applied to newbuild contracts from that date. As from July 2012 most vessels delivered are covered by the new standards. The resolution title is generally referred to in abbreviated form as PSPC. Existing ships built before 2008 and those contracted before then but commenced later are not covered by the regulation.
The PSPC applies only to dedicated seawater ballast tanks in all types of ships above 500gt and double side skin spaces in bulk carriers above 150m loa which are constructed of steel. It does not apply to cargo holds in bulk carriers that are sometimes used for ballast purposes. It is based on a detailed specification and requirements which intend to provide a target useful coating life of 15 years, which is considered to be the time period, from initial application, over which the coating system is intended to remain in “GOOD” condition.
GOOD is not a vague term but is defined as: “A condition with spot rusting on less than 3% of the area under consideration without visible failure of the coating. Rusting at edges or welds should be on less than 20% of edges or weld lines in the area under consideration”. The actual useful life will vary, depending on numerous variables including actual conditions encountered in service.
While there is a requirement for the owner to maintain the coatings to the standards during the life of the ship, the most onerous parts of the regulation is directed at coating manufacturers, coatings contractors and inspectors. The PSPC is formulated around two-coat epoxy coatings but permits alternatives such as Nippon Paints’ NOA 60HS Self-Indicating one-coat epoxy coating system.
Two coats were stipulated for the simple reason that the second and lighter colour coat allows easy identification of areas where coverage has been missed. The one-coat epoxy system has a very different colour depending upon the coating thickness making it relatively easy to see both under and overcoated areas.
The PSPC requirements say that products used for ballast tank coating must be type approved but they go far beyond that simple statement with information on how the type approval process should be carried out. A great deal of the PSPC is about preparation of the tank surfaces and structures. This is understandable given that even the best coatings will fail if surfaces have not been properly prepared. Inspection standards are also covered in the standard.
On delivery of the ship, the owner should also be given a Coatings Technical File (CTF) detailing the coatings used, shipyard work records, type approval certificates, results of inspections during construction and guidance on repair and maintenance. Once the ship is in service, the owner will be responsible for recording all repairs and recoating activities together with appropriate documents. The flag state surveyors should not issue a safety Construction Certificate until the CTF is completed and his own inspection recorded.
One aspect which was not covered in the PSPC that some consider is a serious omission is the potential for some ballast water treatments systems – particularly those that make use of active substances – to be incompatible with the particular coatings used on individual ships. There is a degree of dispute between coatings manufacturers and treatment system suppliers as to which of them should test for compatibility. Some treatment system makers have begun tests with different coatings and can give assurance but with so many systems and coatings on the market there are many permutations and owners should initiate discussions on compatibility at an early stage if later problems are to be avoided.
Four years after the PSPC for ballast tanks was adopted by the IMO, a similar regulation was adopted to cover the cargo tanks of crude oil tankers. It would appear that the move was necessary due to the move from single-hull to double-hull crude oil tankers. The phenomenon of accelerated corrosion in cargo oil tanks had begun to be investigated in the mid to late 1990s when double-hull tankers became common.
A 1997 report by OCIMF suggested that in addition to the more conventional corrosion mechanisms, a possible contributory cause of accelerated corrosion has been microbial attack from bacteria in the cargo oil. It would appear that, as crude oil is often loaded at temperatures higher than ambient air and sea temperatures, during the loaded passage the temperature of the cargo tank structure is being maintained at higher levels than normal due to the insulating effect of the double hull spaces.
A new SOLAS Regulation II-1/3-11, which entered into force on 1 January 2012, on corrosion protection of cargo oil tanks of crude oil tankers, requires cargo oil tanks to be protected against corrosion and makes IMO Resolution MSC.288(87) Performance Standard for Protective Coatings for Cargo Oil Tanks of Crude Oil Tankers mandatory.
These regulations are generally referred to as PSPC COT. As with the PSPC for ballast tanks, the regulation is directed more to the shipyard and coating supplier than to the vessel owner although the obligation to maintain and repair does pass to the owner on delivery.
Since SOLAS did not actually contain a definition of a crude oil tanker it was necessary to address this omission as well. The new regulation came into force in January 2012 and applies to crude oil tankers of 5,000dwt and above for which the building contract is placed on or after 1 January 2013 or in the absence of a building contract, the keels of which are laid or which are at a similar stage of construction on or after 1 July 2013 or the delivery of which is on or after 1 January 2016.
It was already common practice to apply protective coatings in the upper and lower areas of cargo oil tanks but the IMO PSPC COT regulations set out more exact specifications. The following areas are the minimum areas that shall be protected according to the IMO text:
- `Deckhead with complete internal structure, including brackets connecting to longitudinal and transverse bulkheads. In tanks with ring frame girder construction the underdeck transverse framing to be coated down to level of the first tripping bracket below the upper faceplate.`
- `Longitudinal and transverse bulkheads to be coated to the uppermost means of access level. The uppermost means of access and its supporting brackets to be fully coated.`
- `On cargo tank bulkheads without an uppermost means of access the coating to extend to 10% of the tanks height at centreline but need not extend more than 3m down from the deck.`
- `Flat inner bottom and all structure to height of 0.3m above inner bottom to be coated.`
- `Coatings must be type approved according to strict guidelines aimed at simulating exposure to a generic crude oil. The development of a testing protocol for new products was entrusted by the IMO to the International Paint and Printing Ink Council. To undertake this work, the council established a working group that was composed of representatives from class societies, shipowner groups, shipyards, testing laboratories and coating companies.`
The PSPC COT approval process for the actual coating on a vessel follows closely the procedures used in the PSPC for ballast tanks including the requirements for surface preparation, for a CTF and a target useful life of 15 years in GOOD condition for the coating.
##A practical alternative for cargo tanks
Most of the leading coatings manufacturers have developed type approved coatings to meet the standard so compliance should not present any problems for owners. For owners looking for an alternative option to coatings for newbuildings, Japanese class society Nippon Kaiji Kyokai (ClassNK) has developed what it claims as the world’s first set of guidelines for the application of corrosion-resistant steels to the cargo oil tanks of oil tankers. They were accepted as an alternative to coatings as part of Resolution MSC.289(87).
As a result, crude oil tankers over 5,000dwt contracted for construction after 1 January 2013 are able to use corrosion-resistant steel for the inner surfaces of cargo oil tanks. As the use of corrosion-resistant steel eliminates the need for the expensive facilities, preparation and finishing work associated with coating application, while reducing the need for maintenance and coating reapplication, the demand for such steels is expected to grow in the future ClassNK certification was issued for the new NSGP-1 steel (Nippon Steel Green Protect) manufactured by Nippon Steel and confirms that the material complies with the IMO’s new performance standard for corrosion-resistant steels. ClassNK has been involved since the start of development of corrosion-resistant steels, working closely with steel manufacturers, shipyards and shipowners, as well with the IMO and other organisations.
The Guidelines on Corrosion Resistant Steel for COT document was released in January 2012. It is too early to estimate how the cost of corrosion-resistant steel will compare with conventional material through the lifetime of a ship, but the society is confident that any additional cost will be more than offset by avoiding the additional time, labour and resources needed to apply coatings.
##Health and safety
All coatings products contain substances known as volatile organic compounds (VOCs) which are released into the atmosphere during application and curing of the coating. The level of VOCs is frequently controlled by local regulations particularly in the developed world and places such as shipyards may be subject to inspection to ensure rules are being adhered to.
In most instances this will be a matter for the contractor and not the ship operator to concern themselves with. However, VOCs present both a health and fire risk and should be taken into consideration when crew are carrying out any repair and maintenance to coating systems. A prudent operator would include the risk assessment in its ISM procedures and should ensure that any other hazards associated with any particular product are identified from the maker’s material safety data sheets (MSDS) or other issued safety advice.
There are other safety issues for an operator to consider when crew are tasked to work on coatings. These include use of PPE and more generally applying safe practices for working at heights, overside and in enclosed spaces.
More safety related coating issues were highlighted by an announcement by the London P&I Club in October 2016. These include a lack of anti-skid deck paint in key areas, a lack of hazard marking of protruding objects and platforms, and low awareness of the dangers of snap-back zones.
The club recommends that ships’ officers conduct a risk assessment of their mooring stations to establish the best location for anti-skid areas, and the use of a prescribed additive to the deck paint, which can usually be found in the ship’s coating technical file. Good surface preparation is essential to a long life, says the club, as it is believed that 70% of premature coating breakdown on ships is attributable to poor surface preparation.
The club emphasises that hazard markings make trip hazards more visible, and says officers should also not overlook dangers at head height when conducting a risk assessment of a mooring station.
Poor awareness of snap-back zones, meanwhile, continues to feature as a regular negative finding on club inspections. The latest (2015) edition of the Code of Safe Working Practices for Merchant Seaman makes clear reference to a particular industry-wide confusion over the area of snap-back zones being marked on the deck. It states, ‘The painting of snap-back zones on mooring decks should be avoided because they may give a false sense of security’.”
##Dry Cargo Holds
There are no regulations affecting dry cargo holds in the same way as there are for ballast tanks and crude oil cargo tank. However, holds and particularly those in bulk carriers are subject to corrosion and damage cause by the cargo handling methods and the cargo itself. Since the majority of bulk carriers are single-skin vessels, the inside of the hold is also the hull and the double bottom tank tops.
Therefore, any corrosion is likely to affect the structural integrity of the vessel and as a consequence will be given special attention by PSC, P&I and class inspectors and surveyors.
Some typical bulk cargoes such as coal, sulphur and fertilisers can themselves be corrosive and under the appropriate conditions of temperature and humidity can cause severe corrosion wastage in unprotected parts of the structure. For these reasons cargo holds are often coated, usually with epoxy coatings.
The coatings used in cargo holds should be able to withstand physical damage such as experienced when ‘shooting’ hard cargoes such as coal and ores and abrasion and gouging caused by the movement of the cargo during the voyage. Mechanical damage can also be caused by cargo handling equipment such as grabs and buckets used during discharge.
Many leading manufacturers produce coatings specially designed for use in cargo holds. The coatings are notably robust and often of a hard coat type. Because some coatings can contain substances harmful to human health, certificates proving that the coating on a ship is harmless may be required by some administrations.
As cargo holds are quite easy to access, repair to damaged hold coatings is something that is frequently undertaken by crew during periods when the holds are empty. Painting as such is not particularly hazardous but because of the heights of cargo holds accessing some areas does present a safety hazard. Appropriate equipment and safety measures must always be undertaken particularly if working from a suspended platform or using ladders.