Fig. 10 — Rust comes from one of the trunion wheel bearings of this gantry crane above. There was no sign of corrosion prior to the salt water inundation from Hurricane Sandy.
...as any other devices. Usually considered “water-proof” due to the prevalent use of brass materials, many of these critical components go uninspected following a salt water event — only found to be compromised when they are activated.
Brass is severely affected by the salt ions dissolved in sea water. Brass affected by salt can lessen the usefulness of devices such as standpipe or fire hose bib valves following its first exposure to salt water. The failure mode usually involves corrosion between the brass valve stem and brass valve stem guides. Also affected, and usually overlooked, are the associated limit switches used to sense when the valves are actuated.
Any ferrous-based ductwork that takes on salt water is susceptible to corrosion and subsequent failure. Prevalent galvanized ductwork easily corrodes in the presence of salt water. When the inside of the ductwork is affected, corrosion may only be noticed after it has advanced to the point of corroding surfaces from the inside out. Whether or not ductwork surfaces are actually breached, the resulting roughened surfaces of the affected interior areas may create additional drag on airflow when in use, seriously affecting the system’s energy consumption. (Fig. 7)
Mechanical and Process Equipment Mobile and stationary mechanical equipment can trap salt water in critical locations without being noticed by maintenance personnel. The consequences can range from rusted fasteners to oxidized process equipment — causing operating inefficiencies — and on through to damaged load-bearing devices, which can halt equipment operation. Salt residue allowed to remain on threaded fittings can result in plumbing leaks as well. (Figs. 8, 10)
Salt water inundation of structural infrastructure components can create latent issues that manifest themselves years later. Salt ions forced into the cracks of concrete can attack both the reinforcement steel as well as the concrete itself. Both can lead to an incremental decrease in strength, spalling, carbonation of the concrete, and cracking. In addition, the scaling of exposed rebar as a result of contact with salt water, will reduce the grip of newly poured surrounding concrete unless the scale is sufficiently removed. (Fig. 9)
Salt water can also attack polyurethane sealants and mastic adhesives, causing either to lose effectiveness. In the case of urethane sealants, elasticity is reduced. In the case of mastics, adhesion strength is reduced.