piling from corrosion by seawater. The best flame-sprayed zinc coating 

 of the test (5-5 mils thick) failed after h 1/2 years, whereas one of the 

 flame-sprayed aluminum coatings (U.5 mils thick) was still providing ex- 

 cellent protection after 11 1/2 years exposure in seawater. However, 

 when sealed with other types of topcoats, the flame-sprayed zinc was 

 far superior to the flame-sprayed aluminum. For a comparison of flame- 

 sprayed zinc coatings with others, see Figures 11 a-c . Figure lie shows 

 that flame-sprayed zinc in combination with either saran, vinyl, epoxy, 

 or furan have provided good protection to steel piling specimens for 



10 1/2 years. Further testing will be required to determine the maximum 

 duration that these coating systems are effective. Alumbaugh and 

 Brouillette (1966) further report that when a phenolic mastic coating 

 was applied to a flame-sprayed zinc coating blisters occurred before the 

 test specimen was exposed to seawater. 



(2) Flame-Sprayed Aluminum . Flame-sprayed aluminum coat- 

 ings 6, 9, 12, 15 and I8 mils thick on steel panels were evaluated after 

 6 and 12 years of exposure immersed in seawater at Freeport , Texas, and 

 Wrightsville Beach, North Carolina. The results are given in reports by 

 the American Welding Society (1962 and 196T). After 6 years there were 

 small amounts of base metal corrosion on panels from both test sites 

 (American Welding Society, I962). Evaluation of the flame-sprayed alumi- 

 num coatings after 12 years of exposure revealed that all unsealed coat- 

 ings had blistered, but that there were no pits in the steel under the 

 blisters (American Welding Society, I96T ) . 



Some steel panels coated with flame-sprayed aluminum and sealed 

 with a wash primer and vinyl coat have been tested immersed in seawater 

 for up to 12 years. The results of these tests are included under "Vinyl 

 Coatings". Other steel panels with the flame-sprayed aluminum coating 

 were exposed at meantide level for 12 years. The report of the 12-year 

 inspection states that although mean tide level exposure is considered 

 to be more severe in corroding bar steel than total immersion, it ap- 

 peared to be no more severe for steel with flame-sprayed al\iminum or 

 zinc. 



The results of a six-month test of flame-sprayed aluminiMi (Alumbaugh, 

 I96H ) are included in Table III. 



Alumbaugh and Brouillette (1966) report that a i+.5-mil flame-sprayed 

 aluminium coating is still effectively protecting steel in seawater after 



11 1/2 years of exposure. This process used powdered zinc. The fact that 

 a thicker (5 mil) flame-sprayed aluminum coating using aluminum wire had 

 practically failed after 11 1/2 years may or may not be of significance 



as to which is the better application method. 



b. Non-Metallic Coating . This group comprises many coatings, 

 including both organic and inorganic. The earlier non-metallic coatings 

 for steel piling were generally coal tar or asphalt; neither of which 

 has been very successful in seawater. One of the major problems is pene- 

 tration of these coatings by fouling organisms. Coal-tar epoxy coatings 



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