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資料5-4
SUB-COMMITTEE ON SHIP DESIGN AND EQUIPMENT
48th session
Agenda item 12
DE 48/12
19 November 2004
Original: ENGLISH
PERFORMANCE STANDARDS FOR PROTECTIVE COATINGS
Draft performance standards for protective coatings
Submitted by BIMCO, International Association of Classification Societies (IACS), International Chamber of Shipping (ICS), International Association of Dry Cargo Shipowners (INTERCARGO), International Association of Independent Tanker Owners (INTERTANKO)
SUMMARY
Executive summary: This document provides draft performance standards for protective coatings as requested by the Sub-Committee at its forty-seventh session and by the MSC at its seventy-eighth session.
Action to be taken: Paragraph 9
Related document: DE 47/WP.12, paragraphs 18.3 and 18.4 |
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1 At DE 47, the Sub-Committee, in view of draft SOLAS regulation XII/6.4, requested IACS and the industry to develop draft performance standards for protective coatings in double-side spaces of bulk carriers.
2 Consequently, an IACS-Industry Joint Working Group on Corrosion Prevention (JWG/COR - comprised of representatives of IACS, BIMCO, ICS, INTERCARGO, INTERTANKO, OCIMF, as well as one observer from EMSA) was formed and undertook the development of such draft standards that are attached hereto as annex.
Introduction
3 The attached draft performance standard for coating of ballast spaces and similar spaces is based on the following concepts:
.1 the "target useful life" of a protective coating system. This is the durability which should be considered when designing the protective coating system;
.2 performance standard: the target useful life of a protective coating system should be 15 years; and
.3 basic coating specifications for a protective coating system having a target useful life of 15 years.
Technical background
4 JWG/COR agreed that the most practical performance standard is a 15 years target useful life. This is because:
.1 such target useful life, while producing a safety level felt adequate, would lead to an average anticipation for re-coating only once in a ship's life;
.2 a 10 years standard would likely result in more than one re-coat during the ship life (which is a major economical undertaking) as well as provide a lower level of performance; and
.3 a 20 or 25 years standard, besides not ensuring a "re-coating free" ship life, was considered un-practical to be mandated as a minimum standard in view of the additional requirements needed to achieve the extended useful life.
5 From the technical point of view, the attached draft performance standard is based on resolution A.798(19) "Guidelines for the Selection, Application and Maintenance of Corrosion Prevention Systems of Dedicated Seawater Ballast Tanks" and on the industry recommendations provided by the Tanker Structure Co-operative Forum's (TSCF) "Guidelines for Ballast Tank Coatings Systems and Surface Preparation", in particular the TSCF 15 guide for a 15 years system specification.
6 The JWG/COR found TSCF15 to be an excellent basis for the performance standard for the following reasons:
.1 it is a widely used standard for newly built oil tankers, hence it has a well proven record of experience;
.2 although it was originally developed for ballast tanks of oil tankers, the JWG/COR found it applicable to ballast tanks and void spaces of double side skin bulk carriers.
7 Relevant aspects of resolution A.798(19) were judged to be a useful addition to the TSCF15 standard. The rationale being that, since a good performance of the coating system depends on proper steel preparation, application and verification, several aspects of resolution A.798(19) are to be considered as an integral part of a coating standard.
Additional views of the JWG/COR
8 It is the view of the JWG/COR that the Sub-Committee may wish to consider in the future, when and if felt appropriate, the following coating related aspects:
.1 the development of a detailed checklist for the inspections relevant to surface preparation and coating application (see paragraph 3.8.1 of resolution A.798(19));
.2 IMO's Procedures for the Approval of Active Substances (G9), currently under development, should take into account that these substances/chemicals are compatible with the coating system; and
.3 that the JWG/COR consider that the attached draft standard has a general validity as far as ballast water spaces are concerned hence its application need not be limited to the double side skin spaces of bulk carriers. Therefore the Sub-Committee may wish to take the annex into account if the matter of coating of ballast tanks in bulk carriers and/or oil tanker will be addressed in the future.
Action requested of the Sub-Committee
9 The Sub-Committee is invited to note the above comments and the instructions at annex and take actions as appropriate.
For reasons of economy, this document is printed in a limited number. Delegates are kindly asked to bring their copies to meetings and not to request additional copies. |
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ANNEX
[DRAFT] PERFORMANCE STANDARD FOR PROTECTIVE COATINGS OF THE DOUBLE-SIDE SKIN SPACES OF BULK CARRIERS AND OF BALLAST TANKS
1 DEFINITIONS
For the purpose of this standard, the following definitions apply:
a. abrasive inclusions: are abrasive particles shot into the surface of the steel;
b. ballast spaces: are spaces that can be used for storing ballast water. They normally include, but are not limited to, ballast tanks as defined in resolution A.798(19) and resolution A.744(18) and tanks which, according to the ship's loading manual, can be used for both cargo and ballast;
c. dew point:: is the temperature at which air is saturated with moisture;
d. NDET: is the nominal dry film thickness;
e. hard coating: is a coating that chemically converts during its curing process or a non-convertible air drying coating which may be used for maintenance purposes. Can be either inorganic or organic;
f. primer coat: is the first coating applied in the shipyard (to differentiate it from shop-primer);
g. shop-primer: is the prefabricated thin primer coating applied to steel plates, often in automatic plants;
h. solvent: is a volatile liquid capable of completely dissolving a given binder;
i. stripe coating: is an application, normally by brush, of one or more coating layers on locations where it is not easy to achieve the final total dry film coating thickness with the simple spray applications;
l. target useful life: is the target value, in years, of the durability for which the coating system is designed. It is noted that the design of a coating system includes criteria for selection of the coating and for its proper application;
m. thinner: is a volatile liquid that does not necessarily dissolve the binder, but which is capable of reducing the viscosity of the binder solution (vehicle), for example in reducing the viscosity of a paint spraying consistency.
2 GENERAL PRINCIPLES
2.1 The ability of the coating system to reach its target useful life depends on the type of coating system, steel preparation, and regular coating inspection and maintenance. All these aspects contribute to the good performance of the coating system. All are dealt with in this document with the exception of regular coating inspection, which is covered by resolution A.744(18), and maintenance.
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