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Tank coating rules

Updated 17 Oct 2019

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Regulations governing coatings on ships do not extend to all of the various types of coating and areas of the ship that are coated. The most regulated is of course the hull and the anti-foulings used to limit marine growth. Beyond this, only three areas are subject to IMO regulations and these are places where corrosion and degradation of the ship’s structure frequently occur. Because of limited access to these areas in normal operation, rules have been put in place to address the specific concerns.

Ballast tanks and bulker voids

Every shipowner should know that ballast tanks have historically proven a troublesome part of the ship to maintain and 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 was sometimes such that difficult-to-spot deficiencies were overlooked.

As work at the IMO on the 2004 Ballast Water Management Convention was coming to a close, attention there and in IACS turned to addressing the issues of ballast tank coatings.

In 2006 at MSC 82, 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 resolution title is generally referred to in abbreviated form as PSPC.

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 but existing ships built before 2008 and those contracted before then but commenced later are not covered by the regulation.

In practice, shipbuilders are responsible for implementing the PSPC requirements during new construction. Before construction begins, the yard, class society and coatings sub-contractors agree surface preparation, coating process and inspection procedures. The details are entered into the ship’s Technical Coating File along with full details and MSDs of the products used.

Cargo tanks

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 the Oil Companies International Marine Forum (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.

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.

The cargo holds of dry cargo vessels and bulkers in particular are other areas that are prone to damage and can become starting points for corrosion. It should be standard practice to inspect the conditions of holds on a regular basis. In many instances, charter parties will call for the holds to be clean and dry and free from scale and corrosion and inspections will take place before loading. However, this is not a universal requirement for all cargoes.

Coal and ores are particularly notorious for causing damage to hold coatings and coal can have a high sulphur content that can initiate corrosion. Regular inspections should pay particular attention to areas where cargo may lodge and especially to any ladders and their securing to the hold.

VOCs and other coating related health risks

Virtually 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. The latter can be especially dangerous considering the potential for low oxygen levels to begin with and VOC released from the coating being applied.

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.”

Paints also have a different role to play in general safety. It is standard practice for escape routes to be marked with yellow paint and the use of different colours for painting pipes gives an indication of what fluid or gas they may be carrying. Similarly, arrows painted on pipes and the like can indicate direction of flow. Care should be taken to ensure that any touching up or repainting is done using the same colours as the originals.

Cutting or welding of any painted surface should take into account the properties of the paint used. Failure to do this can result in the release of harmful vapours and in most cases a fire risk. Eye protection should always be worn when working in painted areas especially if preparing for repainting because of the risk of paint chips striking eyes. When preparing old paint surfaces, the danger of dust from the paint should not be underestimated. Rubbing down wet is a sensible precaution. PPE must be worn when using paint strippers because of their caustic nature.

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