The results showed excellent corrosion resistance for electroless nickelplated steel embedded in concrete specimen exposed to outdoor or seawater. The chlorine contents of concrete specimens increase as the days of immersing time in seawater pool increase during 500 days. Another steel bond strength test revealed that the electroless nickelplated steel has similar performance as the conventional one. This means that the electroplating has no significant impact on steel bond strength. In most cases, the reinforcing steel bar which was coated with an electroless nickel-plated film showed a reduced corrosion probability.
In recent years, more and more incidences of problems with corrosion of reinforcing steel in concrete structures have been reported throughout the world. While there are several different theories on how steel corrodes in concrete, the problem is known to be associated with high concentration of chloride ions in the concrete and is especially severe in marine environments, coastal regions or where deicing salts are used. Steel embedded in concrete is normally protected from corrosion by an alkaline environment provided by the concrete cover. However, when chloride ions penetrate into the concrete, the PH of the concrete is reduced and this protective environment can be destroyed (Lee and Lee 1998). Corrosion protection for rebar has been provided usually by coating the rebar with an epoxy. It has been assumed generally that epoxy coated rebar is immune to corrosion. However, performance of concrete structures using epoxy coated rebar has pointed to the contrary. Among a great number of examples of failures is the Long Key Bridge in Southern Florida, which showed severe signs of corrosion-related spalls within seven years after construction. Numerous additional spalls developed in other parts of the bridge substructure during subsequent years (Sagues 1994). In addition, corrosion spalls began to appear also in the substructure of other Keys bridges built with epoxy-coated rebar at about the same time as the Long Key Bridge.
