Piers and docks

Ferrous-Base Metals. Steel. Steel finds wide use in sea water, especially as a structural material such as for ships, off-shore drilling towers, piling for piers and docks, and sea walls. It is also used as piping to handle sea water. Compared to other metals, steel is one of the least expensive materials of construction. 

Reinforced concrete structures exposed to marine environments suffer premature corrosion-induced deterioration by chloride in seawater. Corrosion is typically found in piers and docks, bulkheads and retaining walls, mooring structures and navigational aids. 

Atmospherically exposed submerged zones typically experience the greatest corrosion. These zones are found on piers and docks (ladders, railings, cranes, and... 

Epoxy coatings cost approximately 4.7-5.3/l while antifoulants are more expensive at 11.8-21.1/1. Environmental regulations have led to decreased amount of chemicals released from industrial installations along waterways, especially corrosives such as chlorine. The materials of construction for some water structures have also changed. Piers and docks are no longer constructed with wood, but instead are constructed with steel-reinforced concrete. To improve the lifespan of the structure and prevent corrosion of reinforcing steel, fusion-bonded epoxy-coated reinforcement or corrosion-inhibiting admixtures are sometimes utilized in the concrete mix. 

While ordinary carbon or alloy steel is used most commonly for reinforcement or prestressing of concrete, stainless steels have been used in construction of piers with special service requirements [/] or in critical areas on other structures [2]. Other materials such as reinforced pktstics and nickel-copper alloy 400 have been used also to a limited extent or have been proposed for use as reinforcement for concrete in piers and docks. Stainless steel clad carbon steel is a relatively new development and its use for reinforcement of marine structures currently is being evaluated. Epoxy-coated carbon steel reinforcement also has been used successfully in many marine applications, but some failures have occurred. 

Cathodic protection is used widely for the protection of submerged steel in waterfront structures. It also can provide considerable benefit in the intertidal zone and can even reduce the usually high corrosion rate experienced at the boundary between the intertidal zone and the splash and spray zone. Cathodic protection also is used to prevent corrosion of the soil side of steel in marine structures such as sheet steel bulkheads. Cathodic protection also is effective in the control of the corrosion of reinforcing steel in concrete in all exposure zones in waterfiont structures. Particularly for impressed current systems, it is important to select materials for the cathodic protection system components such as rectifiers and junction boxes with consideration of the environment to which they will be exposed. When considering cathodic protection, periodic inspection and maintenance is required for proper system operation. The costs for inspection and maintenance must be considered in the overall cost of cathodic protection. While there are no specific standards for cathodic protection of piers and docks, information in NACE RP0176 (Corrosion Control of Fixed Offshore Platforms Associated with Petroleum Production) and NACE RP-0187 (Design Considerations for Corrosion Control of Reinforcing Steel in Concrete) contain information that is applicable to marine piers and docks. 

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