coating conditions in water ballast tank, void space and cargo oil ...

Shipbuilding Technology ISST 2007, Osaka, 2007
COATING CONDITIONS IN WATER BALLAST TANK, VOID SPACE AND CARGO OIL
TANK OF AGED SHIPS AND REQUIRED PERFORMANCE STANDARD OF
PROTECTIVE COATINGS FOR NEW SHIPS
Takanobu Murakami, Shin Kurushima Dockyard Co., Ltd.
Takayuki Sasaki, IHI Marine United Inc.
Masahiro Kuwajima, Mitsui Engineering & Shipbuilding Co., Ltd.
Masanobu Koori, Mitsubishi Heavy Industries, Ltd.
SUMMARY
PSPC (Performance Standard for Protective Coatings) for water ballast tanks and double hull spaces of bulk carrier was
adopted at MSC82 as resolution MSC.215(82) in last December, and protective coatings for void spaces was discussed
at DE50 in March this year. Furthermore, protective coatings for cargo oil tanks have been discussed at JWG (Joint
Working Group) of IACS, and the proposal of JWG will be submitted to IMO.
We, members of SAJ (the Shipbuilders’ Association of Japan) participated in all discussions and introduced the actual
situation of ship’s coating through the results of several investigations.
In this paper, we would introduce the coating conditions of the ships aged more than 10 years in water ballast tanks, void
spaces and cargo oil tanks with some photos, and express our considerations regarding the relation between tank coating
at new building stage and the coating conditions of aged ships.
1. INTRODUCTION
In these couple of years, coating standard including
surface preparation and coating application has been
discussed for the purpose of enhancing the safety of ships.
It has been expanding from double hull space of bulk
carrier to water ballast tanks and void spaces of all kinds
of ships, and further to cargo tanks of oil tankers.
Discussion in IMO on the coating standard for water
ballast tanks was started based on TSCF15 (15 years
specification issued by Tanker Structure Co-operative
Forum). During the discussions at IMO meetings and in
corresponding group, we have repeatedly express our
view on the effectiveness and practicability of the
standard.
With regard to the expansion of the standard to void
spaces and cargo oil tanks, NMRI (National Maritime
Research Institute) and SAJ carried out the inspection of
ships to clarify the actual coating conditions of aged
ships in order to know the necessary specification and
application of coating for 15 years target life.
In this connection, we would show our considerations on
the necessary standard for each spaces of ship, i.e. ballast
water tanks, void spaces and cargo oil tanks.
2. NEW REGULATIONS FOR PAINTING
2.1 WATER BALLAST TANKS
As for water ballast tanks, new regulation was adopted as
resolution MSC.215(82) in last December.
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The summary of the resolution is as follows;
a) The resolution shall apply to ships of not less than 500
gross tonnage:
for which the building contract is placed on or after 1
July 2008; or
in the absence of a building contract, the keels of
which are laid or which are at a similar stage of
construction on or after 1 January 2009; or
the delivery of which is on or 1 July 2012.
b) The resolution shall apply to all dedicated seawater
ballast tanks arranged in ships and double side skin
spaces arranged in bulk carriers of 150 m in length
and upwards.
c) CTF (Coating Technical File) shall be kept on board.
d) Inspection work shall be done by qualified inspectors
certified to FROSIO LevelⅢ or NACE Level 2 or
equivalent.
e) Epoxy type multi-coat system with stripe coats shall
be applied.
f) Coating system shall pass pre-qualification test.
g) NDFT (nominal dry film thickness) of 320μm with
90/10 rule shall be applied.
h) Free edges shall be treated to rounded radius of 2 mm,
or by three pass grinding or equivalent process.
i) Damaged shop primer and welds shall be blasted to Sa
2 1 /2.
j) After erection, butts shall be treated to St 3 or better or
Sa 2 where practicable. Small damages up to 2% of
total area shall be treated to St 3, and contiguous
damages over 25 m 2 or over 2% of the total area of the
tank shall be treated to Sa 2 1 /2 respectively.
k) Requirements of surface cleanliness such as oil
contamination, dust, water soluble salts are prescribed

Shipbuilding Technology ISST 2007, Osaka, 2007
Guideline for implementation of MSC.215(82) is being
discussed in IACS/JWG for practical and consistent
application.
2.2 VOID SPACES
PSPC for void space was discussed at DE50 in March
this year. As the output of DE50, the draft resolution will
be submitted to MSC83. While the meeting in DE50, we
proposed the practical standard based on the inspection
results for void spaces of aged ships.
The summary of the draft resolution is as follows;
a) The draft resolution shall apply to bulk carriers and
oil tankers as recommendation basis until the SOLAS
amendments to make it mandatory will be adopted.
b) Definition of void spaces is clarified.
c) Epoxy based paint and NDFT of 200μm with 90/10
rule shall be applied.
d) Free Edges shall be treated by one pass grinding or
equivalent.
e) Damaged shop primer shall be treated to Sa 2 or St 3.
f) After erection, butts shall be treated to St 3 or better
or Sa 2 where practicable.
g) One stripe coat shall be applied to thermally cut free
edges and small holes only.
h) Requirements for dust quantity and soluble salts limit
are relaxed compared with those for water ballast
tanks.
2.3 CARGO OIL TANKS
European countries and shipowners’ and oil companies’
associations submitted their proposal of new SOLAS
regulation to MSC82 which make PSPC for cargo oil
tanks mandatory. In this connection, Japan submitted the
proposal of using corrosion resistance steel in the cargo
oil tanks as an alternative.
DE50 instructed the correspondence group to develop the
draft new SOLAS regulation regarding cargo oil tank
protection for the discussion at DE51. The development
of PSPC for cargo oil tanks will be further considered at
DE51.
3. REPORT ON THE COATING CONDITION
OF ACTUAL SHIPS
3.1 INSPECTED SHIPS
In order to investigate appropriate coating standard, three
(3) aged ships were inspected. Outline of the inspected
ships are shown on Table 1.
Table 1. Inspected ships
Ship A Ship B Ship C
Type of Ship Tanker
Tanker
Bulk Carrier
(VLCC)
(VLCC)
(PANAMAX)
Age of Ship 15 years old 12 years old 11 years old
Shipyard Japanese Japanese Japanese
Operator Japanese company Japanese company Japanese company
Major Sea Route East Asia – Middle East East Asia – Middle East East Asia – Oceania
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Shipbuilding Technology ISST 2007, Osaka, 2007
3.2 WATER BALLAST TANKS
3.2.1 COATING SPECIFICATIONS IN WATER
BALLAST TANKS
Coating specifications in water ballast tanks of inspected
three (3) ships are shown on Table 2.
Table 2. Coating Specifications in Water Ballast Tanks
Ship A Ship B Ship C
Type of Paint Tar Epoxy paint Tar Epoxy Paint Tar Epoxy paint
Dry Film Thickness 200μm
200μm
220μm
(1spray)
(1spray)
(1spray)
Stripe coat Not applied Holes and narrow spaces Not applied
Primary surface preparation Sa2.5 (shot blast)
Sa2.5 (shot blast) Sa2.5 (shot blast)
IZP
IZP
IZP
Steel Free edge Removed burrs 1 pass grinding 1 pass grinding
condition Weld bead No treatment No treatment No treatment
Surface treatment St 3 St 3 Sa2.5 (Partially St3)
3.2.2 OVERVIEW IN THE WATER BALLAST
TANKS
Ship A)
Photo-A-W-1
Photo-A-W-2
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Photo-A-W-3
These photos show deck head areas under upper deck,
and these areas are considered to be in severest condition
for corrosion. There were some areas of which condition
was worse than of these photos and deck plates of such
areas had cut off for renewal work.

Shipbuilding Technology ISST 2007, Osaka, 2007
Ship B)
Photo B-W-1
Photo B-W-2
Photo-B-W-3
These photos show middle areas in height. Some rust
was initiated from edges, welds, small fittings and small
holes.
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Deck head areas of this ship had already recoated at
previous docking and kept good condition.
Ship C)
Photo C-W-1
Photo C-W-2
These photos show middle areas in height.
Rust was initiated from edges and welds and spread to
surrounding.
3.3 VOID SPACES
3.3.1 COATING SPECIFICATIONS IN VOID
SPACES
Coating specifications in void spaces of inspected three
(3) ships are shown on Table 3.

Shipbuilding Technology ISST 2007, Osaka, 2007
Table 3. Coating Specifications in Void spaces
Ship A Ship B Ship C
Coating type Alkyd based Tar epoxy Surface-tolerant epoxy
Dry film thickness 70μm
125μm
100μm
(2 spray)
(1spray)
(1spray)
Stripe coat Not applied Not applied Not applied
Primary surface treatment Sa 2.5 (Shot blast) Sa 2.5 (Shot blast) Sa 2.5 (Shot blast)
IZP
IZP
IZP
Steel Free edge No treatment No treatment No treatment
condition Weld bead No treatment No treatment No treatment
Weld spatter Loose spatter to be Loose spatter to be Loose spatter to be
removed by scraper removed by scraper removed by scraper
Surface Grade St 2
Between St 2 and St 3 Loose rust to be brushed
treatment
(By disk sander and/or (By disk sander and/or
off.
power brush)
power brush)
Treated area Damaged shop primer, Damaged shop primer, Damaged shop primer,
welds and rusted areas welds and rusted areas welds and rusted areas
Water soluble salt Removed to the extent invisible to the naked eye.
Oil contamination Removed. The traces may be visible.
3.3.2 OVERVIEW IN THE VOID SPACES
Ship A)
Photo-A-V-1
Photo-A-V-2
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Photo-A-V-3
Almost all areas were in quite good condition. Slight rust
was found on the welds in Photo-A-V-2 and at the edge
of manhole in Photo-A-V-3, but did not spread further.

Shipbuilding Technology ISST 2007, Osaka, 2007
Ship B)
Photo-B-V-1
Photo-B-V-2
Photo-B-V-3
All areas including edges and welds were in perfect
condition. Photo-B-V-3 shows a part where main coating
was not applied and shop-primer was exposed. Slight rust
was found on the shop primer damaged during
construction, but good condition was kept where shopprimer
was intact even without main coatings.
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Ship C)
Photo C-V-1
Photo-C-V-2
Photo-C-V-3
Almost all areas were in quite good condition. There
were small mechanical damages at the edge of opening in
Photo-C-V-2, but the rust did not spread further. Some
rusted areas caused by mechanical damages were
appeared on the floor in Photo-C-V-3, but the rust also
did not spread further.

Shipbuilding Technology ISST 2007, Osaka, 2007
3.4 CARGO TANKS
3.4.1 COATING SPECIFICATIONS IN CARGO
TANKS
Coating specifications in cargo oil tank (slop tank) of
inspected two (2) ships are shown on Table 4.
Slop tanks were inspected because ordinary cargo tanks
were not coated.
Table 4. Coating Specification in Cargo tanks
Ship A Ship B Ship C
Type of Paint Tar Epoxy paint Tar Epoxy Paint -
Dry Film Thickness 200μm
200μm
-
(1spary)
(1spray)
Stripe coat Not applied Holes and narrow spaces -
Primary surface preparation Sa2.5 (shot blast)
Sa2.5 (shot blast)
-
IZP
IZP
Steel
Free edge Removed burrs 1 pass grinding -
condition Weld bead No treatment No treatment -
Surface treatment St 3 St 3 -
3.4.2 OVERVIEW IN THE CARGO TANKS
Ship A)
Photo A-C-1
Photo A-C-2
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Photo-A-C-3
These photos show rusted areas of deck head under upper
deck.A lot of rust was found but the condition was much
better than in water ballast tanks of this ship, and plate
thickness loss was quite small.
Ship B)
Photo B-C-1

Shipbuilding Technology ISST 2007, Osaka, 2007
Photo B-C-2
Photo B-C-3
Overall coating was still in good condition. Coating
damages were observed mainly on upper deck plate and
on fillet welds of upper deck longitudinal.
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4. CONCLUSION
From the results of the inspection, it is considered as
follows;
4.1.1 WATER BALLAST TANKS
・ Deck head area under upper deck seems to be in quite
severe environmental condition, while other regions
are comparatively in mild condition.
・ In general, rust is initiated from edges and welds, and
good treatment on edges and welds will prevent rust
initiating.
・ Apparently, coating specifications of the ships for
water ballast tanks at new building don’t satisfy 15
years coating life.
4.1.2 VOID SPACES
・ Although all inspected ships had been in use for 10 to
15 years, coatings in void spaces were still almost
perfect condition.
・ Very small local corrosions were observed in the areas
prone to be damaged mechanically. (estimated to be
smaller than 0.1% of the total area)
・ Coating specifications of the ships in the void spaces
at new building are sufficient for 15 years coating life.
4.1.3 CARGO TANKS
・ Coatings in the cargo tanks were comparatively in
better condition than those in water ballast tanks.
・ Though some corrosions were observed in deck head
areas, plate thickness loss was quite small, while
recoating or plate renewal was necessary for some of
deck head areas in water ballast tanks of the same ship.
・ Therefore, PSPC for cargo tanks could be relaxed
compared with those required by PSPC for water
ballast tanks.