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It is considered that corrosion of reinforcement induced by chlorides is the biggest problem for the durability of reinforced concrete structures is a mechanism related to the physico-chemical structure and the external environment (Helena, 1993 ).

It is often observed, particularly in structures exposed to marine environment. The level of localized corrosion, pitting or more often by the formation of micro, observed in the corrosion of reinforcement induced by chlorides. Chlorides into the concrete by the concentration gradient, whose attack is much more intense than
carbonation, resulting in the rapid formation of pits (Brown, 2002; Cascudo, 1997; Elsener, 2002).

In many cases of corrosion during an exhibition open to points near the armor of the highest concentration cloretos16 and / or surface inclusions or passive layer of steel. (Cascudo, 1997, Brown 2002).

Above a certain concentration of chloride, passivation first start of the dissolution of portlandite layer around the reinforcement due to the increased migration of ions follows the destabilization of the chemical dissolution with little or no layer Passive (leek, Poole, 1990 apud Sakr, 2004). The proximity of chloride increases the migration of ferrous ions in the passive layer while the passive barrier is less effective in respect the last link in the metal. Finally, at some point, the layer ceases to exist and is replaced by an anodic region (TRAUENBERG; FOLEY, 1971 apud GAID 2004).

Despite this explanation, the mechanism by which chlorides accelerate the corrosion of reinforcing is complex and still poorly known (Cascudo, 1997; GAID 2004). Because in the presence of chlorides, the protective layer can be destroyed even at pH values well above 11.5, so the armor around a concentration of
enough chloride (Jung Yoon Sohn, 2003).

The presence of chlorides in concrete, in a concentration exceeding a certain threshold, produces two simultaneous effects: an increase in the conductivity of the electrolyte layer and disruption of the oxide protective armor. The failure of the oxide layer is due to the formation of a soluble complex of iron chloride and chlorides, which makes it permeable and unstable, which facilitates the dissolution of metal ions (Brown, 2002; HELENE, 1993 ; Sakr, 2004; YALQYN; Ergaźn, 1996). After starting the engine, the well begins to function as cathodes (Sakr, 2004).

Electrons liberated in the anodic areas are attracted to the region forming an electric current cathodic Icorr (Sakr, 2004). The difference of potential existing in various places in the concrete, which may be the result of a concentration gradient of chloride own, is the electromotive force opening reactions between the anode and cathode (Thangavel; Rengaswamy, 1998 ).

After the destruction of the passive layer, with the presence of water (moisture) and oxygen, the iron reacts with hydroxyl chloride form of iron hydroxide, Fe (OH) 2, corrosion rust Form may be lost in cross-section of the bar (Brown, 2002; Cascudo, 1997 HELENA, 1993, Neville, 1997; Sakr, 2004):

FeCl2 2H2O + Fe (OH) 2 + 2Cl

The chloride ion can be used several times in the reactions, acting as a catalyst (Brown, 2002; HELENE, 1993; Thangavel; Rengaswamy, 1998):

6FeCl2 6H2O + O2 + + + + 12H-2Fe3O4 12cl

Because of this, once started, even a small amount of chloride can support the mechanism of corrosion and its effect (Brown, 2002; HELENE, 1993; Thangavel; Rengaswamy, 1998).

For not only the concentration of chloride, which governs the loss of passivity in all exposure conditions, but the relation of chloride-hydroxyl (Cl-/OH-) because the hydroxyl ions act as inhibitors. Experiments show that the pH increases, the limit of chlorides of the loss of capacity passivation also i.