Page 278 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

256 CORROSION CONTROL AND PREVENTION

TABLE 4.25 Total Annual Corrosion-Related Costs
Agency Cost (Millions)
US Army Corps of Engineers (maintenance @ 5%) 70.0
US Public Ports – Corrosion-related maintenance 87.3
Corrosion-related replacements 95.0
US Coast Guard – Lighthouse maintenance 23.5
Replace steel ocean buoys 2.0
Paint buoys 5.0
Replace river buoys 2.0
Corrosion-related maintenance 8.6
Total $293.4

steel support piles), bulkheads and retaining walls (steel sheet piling, steel-reinforced
concrete elements, backside, and anchors on structures retaining dredged fill), and
mooring structures and dams (steel gates, hinges, intake/discharge culverts, grates,
and debris booms). Stationary navigational aids suffer from corrosion of support
piles and steel-reinforced concrete pile caps. Floating steel buoys are also prone to
corrosion (Table 4.25).
Typical corrosion control methods for freshwater structures include coatings for
atmospherically exposed steel and corrosion allowances for submerged and splash
zone steel. Dielectric coatings are normally used for structural steel above water,
while galvanizing is often used for railings, ladders, gates, and gratings. Copper con-
taining steel alloys are sometimes utilized for structural elements and sheet pile walls.
These alloys, which form a tenuous oxide film in the atmosphere, provide little protec-
tion when buried or submerged. CP is occasionally used on submerged steel elements.
Marine corrosion control methods also include coatings for atmospherically
exposed steel elements and a corrosion allowance for submerged and splash zone
steel structures. Specialty marine dielectric coatings are normally used for structural
steel above and often below water.
Although galvanizing is used for railings, ladders, gates, and gratings non-ferrous
alloys provide better service in the aggressive saltwater marine conditions. Marine
structures commonly use CP to control corrosion on submerged steel. CP is occa-
sionally used on atmospherically exposed steel-reinforced concrete, in particular, in
warm climates. The most cost-effective corrosion control on submerged and splash
zone steel is achieved by using CP in conjunction with a heavy dielectric coating.
Although corrosion allowances are often used for saltwater marine structures, they
are not as helpful as in freshwater because the corrosion damage tends to be localized
in the tidal zone (wet/dry cycling) and at the mud interface zone.
Although corrosion is a significant issue within waterways and ports, funding for
protection against corrosion is in short supply. Out of 276 lock chambers at 230 sites,
only 191 sites with 237 lock chambers were funded in 1998 toward maintenance
work. Neglected structures include single-pile navigational aids left in service until
failure occurs. It is estimated that a new $15,000 navigational aid is necessary and
the underwater pole needs to be removed.