Handbook of Solvents - George Wypych - ChemTech - Ventech!

1032 Mohamed Serageldin, Dave Reeves
and for other performance requirements such as preventing corrosion and fouling; protecting
cargoes from contamination; providing safety warnings and informational markings;
providing cosmetic and camouflage colors; preventing slipping and sliding on walking surfaces;
reducing fire hazards; and providing cathodic protection. 21 The coating systems of
marine coatings are selected to meet:
• the type of marine environment to which a vessel will be exposed
• the time a vessel is to remain operational before it needs to be reworked.
General areas of a ship include: (1) underwater hull, (2)superstructures and freeboard,
(3) interior habitability areas, (4) exterior deck areas, and (5) fuel, water ballast and cargo
tank. 22 The freeboard is the area above water hull. These areas have different characteristics
and operational requirements. Table 14.26.3 23 shows the predominant resin and solvent
types used on ships based on a 1991/1992 survey of the industry obtained as part of the shipbuilding
and ship repair regulation was being developed. The summary table also gives average
VOC and HAP content for the various coating category types. Epoxy coatings
constitute a large percentage of the coatings used. The epoxy films are strongly resistant to
most chemicals and are very good anti-corrosion coatings, and require little surface preparation.
Table 14.26.3. Summary of marine coating usage (by coating type) 23
Coating types
General use types
Average usage in
U.S. shipyards, %
Average VOC
content, g/L (lb/gal)
Average HAP
content, g/L (lb/gal)
alkyd based 10 474 (3.95) 355 (2.98)
epoxy based
Speciality types
59 350 (2.92) 56 (0.47)
antifouling (multiple resins) 1
11 388 (3.23) 268 (2.25)
inorganic zinc based 10 545 (4.54) 274 (2.30)
other speciality categories 10 400 (3.33) 144 (1.20)
TOTAL 100
1 resins: epoxy, polyurethane, vinyl, and chlorinated rubber
The coating system used will depend on service requirements. Maximum protection at
an economical price can be achieved when the user understands the protection needed and
the functions performed by the coatings. Coatings are designed for spray viscosity, drying
time, pot-life, and cure profile; all of these parameters affect shelf stability. 24 The physical
parameters and properties of a coating are affected by the volatile constituents (mainly organic
solvents) in a coating, some of which are VOCs, HAPs, ozone depleters, and SARA
313 toxic chemicals that need to be reported. 25
14.26.6 THINNING OF MARINE COATINGS
The sprayability of a coating is determined by its viscosity at application. The viscosity is a
measure of the ability of a material to resist flow and is an important formulation design parameter.
Application viscosity is affected by the ambient conditions and by the degree of