5.1.2
Safety. Refer to the Recommendations
for entering enclosed spaces aboard ships (resolution
A.864(20)). It is an absolute requirement that all of the ship's
safety and tank entry procedures and policies are adhered to. In addition,
it is strongly recommended that all travel coating squad members are
trained in safe usage of all the equipment and tools to be used for
the project on board, before being sent to the ship.
5.1.3
Salt contamination will cause
accelerated deterioration of the maintenance coating if not removed
prior to coating application. A recommended procedure to reduce salt
contamination is to remove loose rust scale followed by good fresh
water rinsing, if possible. This should be the starting point in any
surface preparation process in ballast tanks on board ships.
5.1.4
Rust scale that is not removed
prior to coating application will cause early failure. Loose top-scale
is easy to remove, however the inner (black) hard scale is much more
adherent. When over-coated it will soon detach between the steel and
the scale and come off, typically with the coating adhering very well
to the outside of it. If the hard scale cannot be removed, the service
life expectancy of the treatment is 1 to 2 years regardless of the
coating used.
5.1.5
Pitting corrosion is a common
problem in ballast tanks that have been exposed to seawater for some
time. If it has been accepted that the pits need not be welded up,
in order to prevent further accelerated damage, a coating should be
applied. Soluble salts will be present within the pits and it is essential
that these are removed otherwise corrosion will soon start inside
over-coated pits, affecting the service life. Various methods of salt
removal from pits have been proposed for long term repair, however,
for shipboard maintenance purpose, high pressure fresh water washing
is highly recommended, if available.
5.1.6 When Microbiologically Influenced Corrosion
(MIC) is involved, the pits are of a much wider nature, typically
shiny clean inside with sharp edges to unaffected surrounding
steel and often with a foul smell, like rotten egg, being evident
when breaking up the scale cap. An MIC attack can proceed very deep,
very fast.
5.1.7
Temperature is a critical parameter
to consider. When trading in cold water, it will be hard to keep the
inside tank surfaces free from condensation and to cure the coating
in a timely manner. Plan, if possible, the maintenance operation for
periods, or locations, of warmer water.
5.1.8
Condensation is always a risk
on board ships. It is advisable that the crew have a good understanding
about relative humidity and its relation to substrate temperature
and dew point. To paint over a surface that is at or below the dew
point, or that will be at or below the dew point while the coating
is wet, will not perform. Ideally the temperature should be at least
3°C above the dew point.
5.1.9
Ventilation is a vital factor.
This is one item that clearly supports both the quality of the application
and the safety of the operation. Arrange the ventilation that it extracts
from the lowest and furthest corners to ensure the fast and efficient
removal of dangerous solvents. The use of solvent free coating systems
does not mean that ventilation is not required.
5.1.10
Compatibility of coating systems is
of utmost importance for a good end result. To ensure compatibility
of coating systems, using the same coating system as was originally
employed is recommended. If this is not possible, the paint manufacturer
recommendations should be followed. When applying touch up, the intact
coat next to the damaged area should be feathered for good adhesion.