Section 2 Coating breakdown

2.1.1 Naval ships are built with very little (if any) redundancy in structure and any corrosion could seriously affect structural integrity. The Rules require that all steel work be protected by a suitable coating, see Vol 1, Pt 1, Ch 3, 5.4 Examination and testing – Additional items for steel ships 5.4.3 and Vol 1, Pt 6, Ch 6, 3.1 General of the Rules for Naval Ships.

2.1.2 In naval ships all tanks and compartments are usually coated. A breakdown of coatings will lead to corrosion. Coating condition can be graded as GOOD, FAIR or POOR (see Vol 1, Pt 1, Ch 3, 1.5 Definitions 1.5.8 of the Rules for Naval Ships). Only these terms are to be used for reporting coating of structure deterioration. These definitions also refer to the corrosion condition of steel structure.

2.1.3 A protective paint coating system will normally be a hard coating. However, other types of paint coating or corrosion prevention system may be considered as an alternative to hard coating, details of which should be forwarded to LR Headquarters prior to acceptance for use.

2.1.4 It should be noted that Vol 1, Pt 3, Ch 6, 6 Protective Coatings of the Rules for Naval Ships, requires that salt water ballast tanks, in new construction, which have boundaries formed by the hull envelope, are to have a corrosion protection coating system applied in accordance with the manufacturer’s recommendations.

2.1.5 Corrosion is a major cause of defects in water ballast tanks and varying corrosion levels can be present in the same tank. This is often exacerbated in those tanks where protective coatings have broken down, or where tanks are adjacent to machinery spaces, fuel oil/DIESO tanks, or otherwise subjected to large changes in temperature. Water compensated fuel tanks can also be sites of extensive corrosion.

2.1.6 The repair of a tank coating, or the replacement of a corrosion prevention system, should be in accordance with the manufacturer’s requirements or recommendations.

2.1.7 If it is proposed to supplement an existing hard coating, which has broken down, by fitting anodes, details of the anodes should be recorded and reported.

2.1.8 Owners/Naval Authorities should be encouraged to maintain salt-water ballast tank coatings in a ‘GOOD’ condition and, when found to be in a ‘FAIR’ condition, to reinstate coatings to their original condition. When found to be in a ‘POOR’ condition, the Owner/Naval Authority should be advised that coatings must be repaired. When coatings are not repaired, spaces are uncoated, or a soft coating has been applied, then these are to be considered as ‘critical areas’ from the corrosion aspect, and should be included in the Hull Memoranda for examination at each Annual Survey.

2.2.1 The common practice adopted in naval ships for lagging removal is to remove 300 mm² panels at the forward, midship and aft ends of main watertight bulkheads at three positions: deck, deckhead and between these two.

2.2.2 This practice may be adopted at the Surveyor’s discretion, to prevent wholesale lagging removal at surveys.

2.2.3 The Surveyor may also require removal of lagging or coverings in areas that are prone to corrosion, see Ch 10, 3.1 General, or areas of high stress concentration where corrosion and fractures may occur, see Ch 13 Fractures.