Marine tank coatings

Table 11.1. The most important paint systems for marine tank coatings...

Uses Epoxy curing agent for two-pkg. air-dry coatings, e.g., industrial maintenance primers, midcoats, and topcoats, anticorrosive marine primers, zinc-rich primers, methanol-resist, tank coatings, concrete floor coatings... 

Chem. Descrip. Polyamide in Aromatic 100 Uses Curing agent tor adhesives, flooring compds., pipe and tank coatings, marine finishes, castings, potting and encapsulation Properties Gardner 12 color sp.gr. 0.96 dens. 8.0 Ih/gal vise. 2000 cps ... 

Uses Poiysuifide in seaiant/cauik appiics. in building, insulating glass, and marine industries, casting compds., elec, potting compds., and fuel tank coatings... 

The coated aluminum strips were suspended in fresh and salt water tanks containing fresh and marine water sediments, respectively (Figure 11). Fresh water sediment was obtained from the Scioto River (Columbus, OH) and marine sediment was obtained from Tampa Bay (FL) and the pH of the sediments was 7.5 and 7.9, respectively. Each three gallon fish tank contained 6 liters of distilled water and 305 grams of the appropriate sediment. To the marine tank, sea salt (0.5 cup/gallon of water) was added. The tanks were stored in the dark and the water was stirred to simulate movement of a boat in water. 

The ambient-cured coatings are extensively used as heavy duty industrial and marine maintenance coatings, tank linings and floor coverings, for farm and construction equipment and aircraft primers and in do-it-yourself finishes. Due to higher reactivity, these are usually available as two-pack systems where the components are mixed immediately before application. 

Complex structures such as tank farms, tank bottoms and marine installations have complicated attenuation patterns and it is not feasible to use complex equations to determine the effect. This must be determined by a current drain test or by practical experience. For pipelines the attenuation depends on the linear resistance of the pipe, coating resistance, and to some extent the resistivity of the soil. Connections to foreign structures and the method of termination of the line also affect the attenuation (see Section 10.1). 

Epoxy-silica hybrids are well known for their abrasion resistance and low thermal expansion due to the presence of nanostructured bi-continuous domains. Most recently they have entered the market as anticorrosion coatings in the marine held, for yachts and for large metal vessels, such as oil tankers, and in particular for cargo or ballast tanks and on hulls (Figure 4.9). 

Coal tar pitch is the most widely used resinous extender for epoxy resins. It is primarily used in surface coating formulations, but can also be used as a cost reducer and flexibi-lizer in epoxy adhesives and sealants. In addition to the increase in flexibility (and reduction in thermal and chemical resistance), coal tar pitch extenders provide excellent water resistance. Their primary applications, therefore, are often in the marine, pipe, tank, and general industrial maintenance areas. 

Common uses of the impressed current method of protection include long transmission pipelines, complex underground structures, marine structures, ship hulls, and replacement for dissipated galvanic systems, large condenser water boxes, reinforcing steel in concrete, bare or poorly coated structures, unisolated structures and water storage tank interiors. 

Painting the exposed external surfaces of an AST provides corrosion protection, improved appearance, and reduced evaporation loss. Selection of coating type depends on the tank operating temperature and the presence of insulation that contains minerals and salts that may cause corrosion. External coatings must be able to withstand the effects of weather, ultraviolet light, and industrial or marine atmospheres. 

External corrosion problems in oil and gas production are similar to those in pipelines, but the economic impact on the total cost of production is limited as the lines are shorter and smaller in diameter. Atmospheric corrosion of structures and vessels is a problem for offshore fields and those operating in marine environments. The improved quality of the protective coatings for offshore environments resulted in reduced frequency of repainting platforms and tanks. 

The painting areas of a ship are shown in Figure 11.1. The main requirement of marine coating systems is corrosion prevention. Detailed requirements vary with the particular internal or external area (e.g., chemical resistance in cargo tanks resistance to seawater in ballast spaces heat resistance in engine rooms impact and abrasion resistance on boottoppings, external hulls, and decks cosmetic qualities on superstructure and topsides). 

The environment in chemical tanks is amongst the severest to which marine coatings are subjected. Each tank may have to transport some 1500 bulk, liquid cargoes that include crude oil, refined gasoline, aviation spirit, diesel oil, solvents, vegetable oils, or wine. Inorganic cargoes are also carried in solution (e.g., alkalis and acids). New demands also appear such as methanol as a fuel and feedstock, and methyl rert-butyl ether as an additive for lead-free petrol. 

Chem. Descrip. 2-Hydroxy-4-n-octoxybenzophenone CAS 1843-05-6 EINECS/ELINCS 217-421-2 Uses Lt. stabilizer, UV absorber for plastics and coatings, e.g., polyethylene, PP, PVC, and EVA uses ind. pipe, storage tanks, and auto, marine, garden prods., auto retinish and industrial coatings, adhesives and sealants stabilizer tor food-grade polymers Regulatory FDA 21 CFR 178.2010 (0.5% of polymer), 178.3710 (0.01 %... 

Uses Epoxy tor high-performance, two-package systems tor coatings (structural steel primers, concrete sealers and surfaces, tank linings, container coatings, flooring, and marine coatings)... 

Chem. Descrip. Zinc clad hollow microspheres Uses Filler to build high-mil coatings at less weight, and in zinc-rich coatings for structural steel, marine, automobile underbodies, tank linings, mstdl coils etc... 

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