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2.2 When considering the standard provided in section 3, the following is to be taken into account:
.1 it is essential that specifications, procedures and the various different steps in the coating application process (including, but not limited to, surface preparation) are strictly applied by the shipbuilder in order to prevent premature decay and/or deterioration of the coating system;
.2 proper periodic coating inspection and repair of any damage found during the ship life is necessary and is to be carried out by the operator of the vessel on behalf of the owner;
.3 the coating performance can be improved by adopting measures at the ship design stage such as reducing scallops, using rolled profiles and ensuring that the structural configuration permits easy access with tools and facilitate cleaning, drainage and drying of the space to be coated;
.4 the coating performance standard provided in this document is based on state of the art experience from manufacturers, shipyards and ship operators; it is not intended to exclude suitable alternative coating procedures providing a performance at least equivalent to that specified in this standard is demonstrated. Acceptance criteria for alternative procedures are provided in section 4.
3 COATING STANDARD
3.1 Performance standard
This standard is based on specifications 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 remains in "GOOD" condition according to resolution A.744(18). However, actual useful life will vary depending on numerous variables including actual conditions encountered in service and the frequency and extent of maintenance and repair performed.
3.2 Basic coating requirements
.1 The basic requirements for a coating system meeting the performance standard specified in paragraph 3.1 are listed in Table 1.
.2 Coating manufacturers should give clear evidence of the quality of the product and its ability to satisfy the requirements of Table 1 while the shipyard and/or its subcontractors should provide clear evidence of their experience in coating application.
.3 Detailed criteria for coating selection, job specifications, inspection, maintenance and repair should be agreed by the shipyards and/or its subcontractors, owner and manufacturer in consultation with the Administration or an organization recognized by the Administration, before the ship's construction. These detailed criteria should be documented in an agreed scheme for the selection, application and maintenance of the coating system.
Table 1 - Basic coating system requirements
| |
Characteristic |
Requirement |
Reference standard |
| .1 Design of coating |
| .a |
Selection of the coating system |
The selection of the coating system should be considered by the parties involved with respect to the service conditions and planned maintenance.
The following aspects, inter alia, should be considered:
.1 location of space relative to heated surfaces;
.2 frequency of ballasting/deballasting operations;
.3 required surface conditions;
.4 required surface cleanliness and dryness;
.5 supplementary cathodic protection, if any (where coating is supplemented by cathodic protection system).
Coating manufacturers should have products with documented satisfactory performance records and technical data sheets. The manufacturers should also be capable of rendering adequate technical assistance.
Coatings for application underneath sun-heated decks or on bulkheads forming boundaries of heated spaces should be able to withstand constant or repeated heating without becoming brittle. |
- |
| .b |
Coating type |
Epoxy (or other equivalent hard coating) based.
Multi-coat treatment with coating layers of contrasting colour are recommended.
The top layer of coat should be of a light colour in order to facilitate in-service inspection. |
- |
| .c |
Coating pre-qualification test |
Certified performance test from laboratory corresponding to classification B1 for hard coating. |
TSCF Guidelines for Ballast Tank Coating Systems and Surface Preparation, 2002, Appendix 3, Testing and classification of ballast tank coatings |
| .d |
Number of coats |
As a minimum, two full stripe coats followed by two full spray coats.
Stripe coats beyond the first coat should be applied by brush or roller.
Each coating layers should be adequately cured before application of the next coat, in accordance with coating manufacturer's recommendations.
Intermediate coats must not be contaminated with dirt, grease, dust, salt, over spray, etc.. Job specifications should include the dry-to-recoat times given by the manufacturer. |
- |
| .e |
NDFT (nominal total dry film thickness) |
Minimum 300 μm for epoxy based coatings, other systems to coating manufacturer's specifications.
Maximum according to manufacturer's detailed specifications.
Care should be taken to avoid increasing the thickness in an exaggerated way. Excessive thickness could lead to dangerous consequences, such as solvent and thinner retention, film cracks, gas pockets, etc.. Wet coating thickness should be checked during application.
Thinner should be limited to those types and quantities recommended by the manufacturer. |
- |
| .2 PSP (Primary Surface Preparation) |
| .a |
Steel surface |
The steel surface should be prepared so that the coating selected can achieve an even distribution at the required NDFT and have an adequate adhesion by removing sharp edges, grinding weld beads and removing weld spatter and any other surface contaminant. |
- |
| .b |
Blasting and profile |
SA 2 ½; 30-75 μm
Blasting should not be carried out when:
.1 the relative humidity is above 85%; or
.2 the surface temperature of steel is less than 3℃ above the dew point or;
.3 there is any possibility that the surface of the steel is wet, or there are traces of moisture, or condensation occurs before the primer coat is applied.
Checking of the steel surface cleanliness and roughness profile should be carried out at the end of the surface preparation and before the application of the primer, in accordance with the manufacturer's specifications. |
ISO 8501,
ISO 8503-1/3 |
| .c |
Soluble salt limit |
≤30 mg/m2 |
ISO 8502-9 |
| .d |
Pre-construction primer |
zinc containing, silicate based |
- |
| .3 SSP (Secondary surface preparation) |
| .a |
Steel condition |
Preparation grade P2
Three pass edge grinding of sharp edges |
ISO 8501-3 |
| .b |
Pre washing (fresh water) |
Required |
SSPC SP1 |
| .c |
Water soluble salts limit before SSP |
≤30 mg/m2 |
ISO 8502-9 |
| .d |
Surface treatment |
Sa 2 ½ on damaged pre-construction primer and welds; Sa 2 on intact pre-construction primer, removing 70% of primer |
ISO 8501 |
| .e |
Surface treatment after erection |
Butts Sa 2 ½; small damages (<3% of total area) ST3 |
ISO 8501 |
| .f |
Profile requirements |
As coating requirements |
ISO 8503-1/3 |
| .g |
Dust |
"1" |
ISO 8502-3 |
| .h |
Water soluble salts after blasting/grinding |
≤30 mg/m2 |
ISO 8502-9 |
| .i |
Abrasive inclusions |
None (as viewed without magnification) |
- |
| .4 Miscellaneous |
| .a |
Ventilation |
Adequate ventilation is necessary for the proper curing of coating. Ventilation should be maintained throughout the application process and for a period after application is completed, as recommended by the coating manufacturer. |
- |
| .b |
Environmental conditions |
Coating should be applied under controlled humidity and surface conditions, in accordance with the manufacturer's specifications. |
- |
| .c |
Testing of coating |
Destructive testing should be avoided.
Dry film thickness tests should be carried out after each coat, not just at the end of the coating application, using appropriate thickness gauges. |
- |
| .d |
Inspection |
Inspections relevant to surface preparation and coating application should be agreed upon between the shipowner and the shipyard under the manufacturer's advice. Clear evidence of all the above mentioned inspections should be reported in an agreed format. Such reports should be at the disposal of the interested parties, including the Administration or an organization recognized by the Administration.
The activities that should be verified, inter alia, are:
.1 working conditions, e.g. illumination, access, staging, etc.;
.2 environmental conditions, e.g. temperature and humidity;
.3 removal of sharp edges;
.4 blast cleaning/mechanical cleaning;
.5 cleaning up after blast cleaning;
.6 shielding of painted surfaces from blasting operations;
.7 curing times for individual coats in relation to temperature and humidity;
.8 thickness measurement of each coat;
.9 use and quantity of specified thinner;
.10 continuity of coatings;
.11 storing of coating materials and abrasives;
.12 cleaning of coated surfaces before application of next coat;
.13 handling/storing/transport of coated objects; and
.14 coating repair when damaged. |
|
| .e |
Acceptance criteria |
Following conditions should cause rejection:
.1 excessive sags and runs; isolated sags and runs defined as 1 per each 100 m maximum are acceptable;
.2 pin-holes: none allowed;
.3 air bubbles or air bubble craters: none allowed;
.4 low dry film thickness (DFT): none permissible;
.5 excessive DFT: none permissible with the exception of acceptable sags and runs;
.6 blistering: none acceptable;
.7 lifting or peeling: none permissible;
.8 insufficient dehumidification, heating and/or ventilation;
.9 poor cleaning, presence of inclusions or invisible contamination in excess of the specifications. |
- |
| .f |
Repair |
Any defective areas, e.g. pin-holes, bubbles, voids, etc. should be marked up and appropriate repairs effected. All such repairs should be re-checked and documented. |
- |
| .g |
Health and safety |
Precautions should be taken to reduce health risks, fire and/or explosion risk and other safety risks, in accordance with the regulations of the Administration. |
- |
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4 ALTERNATIVE PROCEDURES
4.1 The performance standard indicated in this document is based on a recognized and commonly used coating system. It is not meant to exclude other, alternative, systems.
4.2 Acceptance of alternative systems will be subject to documented evidence that they ensure a corrosion prevention performance at least equivalent to that indicated in this document, this documented evidence is to be to the satisfaction of the Administration.
4.3 As a minimum, the documented evidence shall consist of satisfactory performance corresponding to a target useful life of 15 years in either actual field exposure (ballast spaces) or laboratory testing.
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