In many cases, service life of reinforced concrete structures is severely limited by chloride penetration until the steel reinforcement. Today, concrete with high resistance with respect to chloride penetration can be produced by internal hydrophobic treatment. The aim of this study was to fill this gap in regards to reinforced concrete structures inserted in a marine environment. Results indicated the efficacy of the hydrophobic agents in cases where capillary suction is the mechanism of water penetration. However, when the transport mechanism is permeability this product is not advisable. Moreover, it was demonstrated that the chloride diffusion coefficient is reduced by the hydrophobic agents, and the corrosion rate of reinforcement could be well protected in the treated concrete with hydrophobic agents of silane. The durability of reinforced structures can be considerably increased and can be accurately designed by the application of an appropriate and optimized protective layer.