steel panels coated with flame- sprayed aluminum, a wash primer 

 and vinyl topcoat were immersed in seawater at Freeport, Texas, and at 

 Wrightsville Beach, North Carolina. Inspection of the panels at the end 

 of 12 years revealed that protection of the steel was excellent with the 

 exception of panels having aluminum 3 mils thick. The other aluminum 

 thicknesses tested were 6, 9, 12, 15 and l8 mils. Panels with the same 

 coating system were also placed at mean tide level for alternate immersion 

 and atmospheric exposure. These panels appeared to be in the same general 

 condition as the totally immersed panels (American Welding Society, 1967). 



Of approximately 21 vinyl coating systems tested in Port Hueneme 

 Harbor, a vinyl mastic had the longest exposure. After 9 1/2 years it 

 was still providing a fair degree of protection to the steel (Alumbaugh 

 and Brouillette, I966). Two other vinyl systems with 6 1/2 and 8 years 

 of exposure were performing very well. The performance of vinyl coatings 

 and other types are given in Figures lla-c and 12. Other findings from 

 these tests were that alumin\am pigmented vinyls showed no conclusive 

 superiority and that failure of vinyl systems could usually be attributed 

 to poor adhesion. 



A coating system consisting of proprietary primer, vinyl, vinyl- 

 alkyd and vinyl antifouling coats was rated in "good-fair" conditions 

 after exposure for nearly 5 years on mooring buoys COrisko, 1968). 

 Three other vinyl coating systems (lO, 11 and 12, Table VIII ) performed 

 poorly and were removed from the test due to failure after approximately 

 2 1/2, 1 1/2 and k 1/^ years, respectively. 



(3) Rubber . Short-term tests by the U. S. Naval Civil 

 Engineering Laboratory showed neoprene synthetic rubber coatings to be 

 relatively good for protecting steel piling from corrosion by seawater 

 in each of the corrosion zones. Tables II a and II b show the ratings 

 given to neoprene coatings after 2 1/2 years of testing on steel piling 

 in the surf zone. 



Steel panels coated with neoprene rubber were exposed in the atmos- 

 phere, at mean tide, and continuously submerged in seawater for 6 years 

 along with 83 other coating systems. Alexander, Forgeson and Southwell, 

 1958 report that a neoprene rubber coating ranked second only to vinyl 

 coatings with antifouling topcoats in the mean tide exposure. Mean tide 

 was stated to be the most severe of the test zones. Table V gives the 

 five top-ranking coatings in this zone. The synthetic rubber coating 

 ranked highest in protecting the steel in the seawater immersion test. 

 It should be noted that the coating was exceptionally thick. 



Chlorinated rubber was used as a seal over flame-sprayed zinc applied 

 to steel panels and exposed to seawater continuously immersed and at mean 

 tide level (American Welding Society, I962). After 6 years of exposure, 

 an inspection of the panels -revealed that the chlorinated rubber seal coat 

 appeared to be completely gone from the specimens totally immersed and 

 from those at mean tide level, and that some of the sealed panels showed 

 more corrosion than the unsealed ones. 



30 



