19 June 2001
ASTM A 572, Specification for High-Strength, Low-Alloy
Columbium-Vanadium Steels of Structural Quality.
ASTM A 242, Specification for High-Strength, Low-Alloy Structural
Steel conforming to ASTM A 690 is recommended for steel H-piles and sheet
piling, because of its greater corrosion resistance over plain carbon steel in the
splash zone. The low-alloy steels offer no more resistance to corrosion than
ordinary carbon steel, however, when submerged. Under this condition, the low-
alloy steels require coatings or cathodic protection, or both. Composite piles of
ASTM A 690 and ASTM A 36, Specification for Structural Steel may be used
when more resistance in the splash zone is required. ASTM A 242 steels are not
recommended for buried structures, submerged conditions, and marine
atmospheres unless they are exposed to the wind, rain, and sun.
Coatings for, and cathodic protection of, low-alloy steels are the same
as for plain carbon steel as discussed in Paragraph 3-4.3.
3-4.1.3 Stainless Steels. Stainless steels have application in the marine
environment under certain conditions. They do well when exposed to wind, rain,
sun, or high-velocity conditions in seawater. In calm or stagnant waters, salt
spray zones, or in buried conditions, corrosion is likely to occur. Stainless steels
in the 300 series (302, 304, 316) are substantially more corrosion resistant than
the 400 series stainless steels. Except in certain atmospheric environments,
stainless steels should only be used for specialized applications where
performance experience has been superior to more commonly used materials to
justify the high cost.
Deterioration of Steel. Although exposure to the atmosphere, severe
temperature changes, and wind erosion all contribute to the deterioration of steel
in waterfront facilities, exposure to saltwater is the major concern. Corrosion
rates of metals exposed to seawater are much higher than those of similar
metals exposed to freshwater.
Biological fouling, the growth of marine organisms on the steel, also
contributes to increased corrosion. This type of fouling can be decreased by
using antifouling coatings.
The other major causes of deterioration are: wave and current effects,
abrasion from objects, and elements in the seawater.
Preventive Maintenance for Steel. The primary preventive measures
available to increase the life of steel are protective coatings and cathodic
protection. The decision of which approach to use is a function of location on the
waterfront structure (submerged or not) and economics. The use of cathodic
protection is restricted to submerged or buried structures.