film. As a single coat system they have outstanding corrosion resistance 

 on coastal structures for protecting metal exposed to aggressive marine 

 atmospheres. They may he topcoated to produce a coating system with an 

 even greater anticipated service life. Inorganic zinc coatings may also be 

 used in industrial environments. In mild industrial environments they may 

 Be used without topcoats. One application, which has found wide usage in 

 the past, is lining hydrocarbon tanks, both on ships and shore. 



Inorganic zinc has excellent abrasion resistance and is often used as 

 preconstruction primer. It must be topcoated for use in aqueous immersion. 

 Zinc coatings offer excellent resistance in the splash zone to saltwater 

 and to freshwater. Zinc-rich primers are often used as primers for organic 

 topcoats such as chlorinated rubber, vinyls, epoxies, urethanes, and 

 certain acrylics in more aggressive chemical atmospheres. It must also be 

 topcoated for continuous immersion in water. Surface preparation require- 

 ment is stringent and application requires skilled workers. 



(14) Organic Zinc . This classification of coating is composed of 

 zinc dust with organic binders such as epoxy resins. Zinc dust content 

 will vary between 45 and 80 percent by volume in the dry film. Performance 

 of the coating is related to the percentage of zinc in the final dry film. 

 Generally, the more metallic the zinc, the better the performance. Organic 

 zinc coatings also show excellent resistance to high humidity splash and 

 spray conditions of both fresh and salt water. Abrasion resistance is 

 somewhat less than the inorganic zinc primers. The organic coatings will 

 tolerate mildly alkaline atmospheres. They are often preferred to "inorganic" 

 zinc as primer for chemical atmospheres because surface preparation and 

 application procedures are less critical. 



(15) Underwater Curing Coatings and Mastics . These materials are 

 two-component 100 percent solids polyamide cured epoxy nonshrinking compounds 

 (sometimes combined with appropriate fillers), designed to chemically 

 displace water on the surface and form a tight bond. Extensive and careful 

 laboratory and field tests, combined with experience information, have 

 shown that good protection can be provided to in-place underwater structures 

 with these mastics. 



They are applied by gloved hand (palming) or trowel to a dry film 

 thickness of 3.2 to 6.4 millimeters (125 to 250 mils), and cure while under, 

 water after several days. Tensile strength, adhesion, impact strength and 

 abrasion resistance are fair to good. They can be used as patching com- 

 pounds to seal metal, concrete, wood, fiberglass and many other substrates 

 specifically in situations where the surface is damp, wet, or under water. 

 The surface preparation recommended is sandblasting for best results. 

 Costs of material and application are very high, $54 to $162 per square 

 meter ($5 to $15 per square foot) . 



(16) Other . There are other special coatings that may be used 

 from time to time for certain applications for coastal structures. These 

 materials are combinations and modifications of the above generic coating 

 classes. They will not be discussed in detail in this report. These 

 coatings include vinyl polyurethanes, epoxy/fiber reinforced mortars and 

 coatings, polyester/glass flake combinations, glass flake/coal tar/ epoxy, 

 100 percent solids urethane/elastomeric membranes, catalyzed hypalon/coal 



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