Marine protection from Jotun

Citation

(1999), "Marine protection from Jotun", Pigment & Resin Technology, Vol. 28 No. 4. https://doi.org/10.1108/prt.1999.12928daf.004

Marine protection from Jotun

Marine protection from Jotun

Keywords: Jotun, Marine corrosion, Paints, Coatings, Corrosion prevention

Now with the Royal Fleet Auxiliary (RFA) rapid response force (RRF), Sea Centurion is the first of Stena Ro-Ro's advanced new "4-Runner" class, and has been protected throughout by Jotun paint systems (Plate 1). A sister ship, Sea Crusader, was scheduled for completion in April 1999, and will also join the RRF flotilla.

The two vessels are the first in a series of the "4-Runner" class to be built at the Viareggio yard of SocietÄ Esercizio Cantieri, and the MoD found it unnecessary to make any changes to the standard specification to meet its requirements for an RFA operated RRF. The 12,350-dwt vessels have a length overall of 182.6m, beam overall of 25.8m and a design draught of 6.6m. They have a speed of 22 knots and offer a vehicle lane length of 2,715m.

Plate 1 Sea Centurion

Jotun Paints manufactures a comprehensive range of marine coatings and, using carefully chosen products from this range, systems can be formulated to give the best possible protection for each differing working area of a vessel. The systems specified for the Sea Centurion are an excellent example.

For the hull below the waterline the Jotun system comprised "Marathon IQ" heavy-duty epoxy, "Safeguard" coal-tar epoxy and "Seavictor 50" tin-free antifouling. "Marathon IQ" is stated to be a high-build, solvent-free coating specifically formulated for resistance to extreme conditions, such as the abrasion likely to be suffered during ice-going voyages. "Seavictor 50" is a TBT-free self-polishing antifouling claiming effective protection for up to 48 months with improved control of green algae.

Blue topside areas of the Sea Centurion, together with her trailer-area sides and overheads, and decks outside the trailer area, are protected by "Jotamastic 87" epoxymastic and "Conseal Topcoat" semi-gloss acrylic. "Jotamastic 87" provides very good resistance to water, solvents and many chemicals. Claiming a low solvent content and no isocyanate, this product is reported to have a much reduced environmental impact. It complies with current NORSOK standards. "Conseal Topcoat" is stated to be quick drying and has good resistance to chemicals and corrosion.

"Jotamastic 87" also provides the principal protection for the white topsides and superstructures of the Stena "4-Runner". On these areas, however, the finishing coat is "Jota-bright Antistain", which reacts with rust staining to make it unobtrusive. On the trailerdeck and ramps, "Jotamastic 87" is used without a topcoat but, as on most other deck areas, an antiskid treatment was included at the surface preparation stage.

Visible internal vertical and overhead steel surfaces throughout the Sea Centurion are protected by a "Mammut" high-build urethane alkyd system, including a white topcoat which, as part of the system, is said to be certified not to spread surface flames.

Numerous other carefully formulated Jotun systems were used to protect surfaces in many varied areas of the Sea Centurion, including accommodation, ballast tanks, engine room, machinery, deck equipment, storage tanks and funnel.

Jotun also reports that following its introduction two years ago, its "Tankguard Special" phenolicepoxy coating system was used to refurbish the cargo tanks of the 18,700dwt Portuguese tanker Galp Leixêes. Recent inspection of the tanks revealed no detachment or blistering of the coating, and only insignificant patches of corrosion.

When, in 1996, the Galp Leixêes drydocked for repair to her cargo tanks, a considerable amount of steelwork needed to be replaced, and the total area cleaned and coated, including both new and remaining old surfaces, was 5,500m2.

The vessel's tanks were surveyed by Jotun and, in accordance with the company's own "Tankcoating Code of Practice for Newbuildings and Ships in Service", the required high standards for the refurbishment were established with the owner and the yard.

The "Tankguard Special" coating system was recommended and comprises three coats, namely, "Tankguard Special Primer" (light red), "Tankguard Special Mid-Coat" (yellow), and "Tankguard Special Topcoat" (grey). For the Galp Leixêes each coat was applied to give a dry-film thickness of 100 microns, with a stripe coat before each full coat on difficult areas.

Jotun state that in addition to an excellent resistance to chemicals and solvents, including petroleum spirit with up to 20 per cent methanol, the "Tankguard Special" system offers very good resistance to water making it ideal for use in tanks containing "grey" water. In addition, the topcoat has a glossy finish and, hence, is easy to clean.

It is reported that at the recent inspection, the cargo tanks of the Galp Leixêes were found to be in excellent condition with no detachment or blistering of the coatings; the gloss finish of "Tankguard Special Topcoat" was found to be virtually "as new".

The tanks were said to be generally clean with cargo residues detected only on some longitudinals and on the tank bottoms. According to Jotun corrosion had occurred on only 0.2-0.3 per cent of the tank-tops, and this was partly due to destaging damage which had not been correctly recoated afterwards. There were also minor spots of corrosion in difficult access areas, and on steps and hand rails, with some staining on flanges.

Following the inspection and assessment. the rust spots on the tank tops were repaired, with a procedure involving degreasing, vacuum blasting to Sa 2.5 standard, washing and touching-up with the three "Tankguard Special" coatings.

In order to obtain the best possible protection, the coating of tanks in a product carrier must be carefully pre-planned and conscientiously carried out, with the work being carefully monitored at all stages. There are many traps for the unwary.

Old steelwork, for example, will often be badly pitted and contaminated with salt. In such a condition, it is imperative that the surfaces are adequately cleaned before new coatings are applied.

Applying a coating over a salt film is a frequent cause of blistering. Although for a ballast tank coating, for example, a salt level of 50mg/m2 is normally acceptable, the much lower level of approximately 10mg/m2 is essential to ensure the expected results from a product carrier cargo tank coating.

It is not always realised that salt contamination is seldom removed by blastcleaning alone, and that high-pressure water washing is needed before the final blastcleaning to Sa 2.5 standard. In some cases, even this procedure will need to be repeated before the steelwork is fit to be coated.

In applying the coating, the manufacturer's recommendations should be strictly adhered to. For example, a stripe coat should be applied, by brush, to all edges, sharp corners, welding seams and other "difficult" areas prior to every full coat.

Details available from Jotun-Henry Clark Ltd. Tel: +44 (0)171 481 2741; Fax: +44 (0)171 265 1836; E-mail: linda.diamond@jotun.co.uk