Profiles showing the pitting rates of the piles concerned in Figure 7 

 are given in Figure 8. 



Tests indicate that when piling is installed where there is con- 

 siderahle movement of abrasive "bottom materials, the portion of the 

 piling subjected to the abrasion will deteriorate at the fastest rate 

 (Ross, 19^+8, Alumbaugh, 1962 ). 



Observation of steel sheet pile groins installed at Palm Beach, 

 Florida, indicated that the localized corrosion rate in the sand abrasion 

 zone could be as high as 373 mils per year (Ross, 19^8). Due to the 

 severity of corrosion in this zone and the distinctive difference in the 

 environment, it is felt that it should be treated as a separate zone 

 when it exists. 



The most severe corrosion zone on steel piling after the abrasion 

 zone is the splash zone when a structure is located where splashing water 

 exists a large percentage of the time. Localized corrosion rates as high 

 as 63 mils per year have been reported for this zone (Rayner, 1952). 



3. Low Alloy Steels 



Various metals have beeri added to steel with the objective of 

 producing steel which is more corrosion resistant in a marine environment. 

 Steel bars containing percentages of copper were tested by immersing in 

 seawater and found to be somewhat more resistant to corrosion than ordi- 

 nary steel (U. K. Department of Scientific and Industrial Research, 1928). 

 However, in alternately wet and dry conditions, steel with higher copper 

 content lost more weight than that with lower percentages of copper. The 

 improved corrosion resistance of copper-bearing steel is attributed to 

 the copper causing a more durable corrosion film to form which retards 

 further corrosion. Ross (19^8) reports that steel sheet pile groins 

 containing copper showed no superiority over ordinary steel in tests at 

 Palm Beach, Florida. Mariner steel piling, containing more copper, silica 

 and phosphorus than A-328 steel, is expected to give 2 to 3 times the 

 corrosion resistance of A-328 steel in the splash zone, depending on the 

 degree of exposure to wave action (U. S. Steel, 196i+). Figure 9 shows 

 comparative corrosion rates for these two steels. 



Section VII. CORROSION PROTECTION FOR STEEL PILING 



1. General 



Methods now used to combat the corrosion of steel structures in 

 seawater include the encasement of steel in concrete, the application of 

 various protective coatings, cathodic protection, and various combinations 

 of these methods . The paragraphs to follow will describe these methods 

 of protection and present information of value when considering their 

 use. 



