Marine durability

Marine durability conditions for adhesive type approval (DNV 2009)... 

Warne, M. A. and Mayfield, P. C. S., Durability Tests on Marine Impressed Current Anodes , IMl Marston/Excelsion Ltd., 15 March (1971)... 

Applications Ion implantation is widely employed to improve the life of tools. Thus press tools, dies and gear cutters can be treated to increase their durability by three times or more. Nitrogen-implanted tungsten carbide drawing dies for copper and iron wire can be improved up to fivefold. By implanting chromium, aluminium or silicon a considerable increase in the corrosion resistance of steel can be obtained. Implantation of chromium into aircraft bearing alloys has improved their durability in marine environments . 

Compared with tar, which has a relatively short lifetime in the marine environment, the residence times of plastic, glass and non-corrodible metallic debris are indefinite. Most plastic articles are fabricated from polyethylene, polystyrene or polyvinyl chloride. With molecular weights ranging to over 500,000, the only chemical reactivity of these polymers is derived from any residual unsaturation and, therefore, they are essentially inert chemically and photochemically. Further, since indigenous microflora lack the enzyme systems necessary to degrade most of these polymers, articles manufactured from them are highly resistant or virtually immune to biodegradation. That is, the properties that render plastics so durable... 

Gravel and crushed rock—stone chips— are obtained by quarrying. Some gravels are collected by sea dredging, which destroys marine environments. However, secondary aggregates, such as crushed rubble from demolition works, offer an alternative to newly quarried materials, and make an attractive, durable surface. 

Extensive information on durability of adhesive joints is more available on aluminum than on other substrates. Figure 15.17 illustrates typical results showing the effect of adhesive variations on joint durability during marine exposure. Vinyl-phenolics and nitrile-phenolics have... 

FIGURE 15.17 Effect of adhesive on the durability of etched 6061-T6 aluminum alloy joints exposed to a marine environment. (1) Two-part epoxy, (2) one-part epoxy, (3) nitrile-phenolic, (4) vinyl-phenolic, (5) vinyl-phenolic.33... 

Differences in performance are also noted depending on the specific nature of the environment. Differences can be expected in joint durability when bonds are exposed to an aggressive wet-freeze-thaw cycle, marine seacoast, or inland environments. Outdoor weathering conditions are often classified by one of the following exposure conditions ... 

FIGURE 15.19 Durability of polyamide-epoxy two-part adhesives exposed to marine atmosphere (fillers are indicated). ... 

However, the corrosion resistance of aluminum as well as the durability of joints made with epoxy adhesives is very dependent on the type of aluminum alloy used. Bonds made with relatively corrosion-resistant 6061-T6 aluminum alloy will last about 4 times as long as equivalent joints made with 2024-T3 alloy when exposed to marine environments. 

Copper substrates are commonly bonded with epoxy adhesives in the microelectronics and marine industries. Compared to aluminum substrates, copper when bonded with epoxy adhesives provides lower initial strength. Depending on the adhesive and the type of test used, this can be as much as 50 percent lower. Similar to aluminum joints, copper joints bonded with epoxy adhesives can show poor durability in moist environments unless the interface is protected. 

Vinyl finish 35 50 60 min 16 h Durable finish coat over high build chlorinated rubber and vinyl systems applied to interior and exterior surfaces in marine and industrial environments... 

The vinyl copolymers can be used most efficiently in special applications such as hospital and dental equipment where durability is more important than initial cost. For laboratory equipment, epoxy resins may be preferred because the vinyls are sensitive to some solvents. The vinyl coating systems consisting of corrosion-inhibiting primer and chemical-resistant finish coats are used on new equipment for chemical plants. The metal conditioner based on zinc chromate and polyvinylbutyral are widely used over sandblasted steel as a use for vinyl systems on both industrial and marine equipment. 

Uralkyds have superior adhesion, hardness, abrasion resistance, durability, and chemical resistance to the unmodified alkyds. They find major applications in wood floor finishes, marine coatings, metal primers, and maintenance paints. 

Very few wood species have sufficient natural durability to allow their use in marine environments without additional protection. Two species that have provided... 

PCP was first introduced in the 1940s as a substitute for ereosote. The aetive ingredient, a chlorinated phenol, is a crystalline solid that dissolves in a variety of organic solvents. The performanee of PCP and the properties of the treated wood are influenced by the ehoiee of solvent. A heavy oil solvent is preferred where treated wood is to be used in ground eontact - wood treated with lighter solvents is not as durable. PCP treated wood has many characteristics and properties that mimic those of creosote, except that it is ineffeetive against marine borers. 

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