Effect Of Cathodic Protection On The Hydrogen Permeability Of The Reinforcing Steel In Concrete

As an excellent building material,reinforced concrete has attracted much attention because of its durability.The corrosion of the reinforcing steel in concrete is a major cause of premature failure of reinforced concrete structures.Cathodic protection can directly control the corrosion process of rebars.This hydrogen evolution reaction can lead to hydrogen embrittlement of the reinforcing steel if the potential gets too negative.In this paper,we investigated the effects of applied potential and chloride ions on the corrosion behavior,hydrogen permeability,and mechanical properties of the reinforcing steel through conventional electrochemical tests,electrochemical hydrogen permeation,and low strain rate tensile testing under in-situ hydrogen charging.The optimal protection potential of the reinforcing steel in a saturated calcium hydroxide solution is-0.85 V,and-0.75 V in a saturated calcium hydroxide solution containing 3.5%NaCl.The positive shift of the optimal protection potential confirmed the synergistic effect of chloride ions and hydrogen generated at a more negative potential.Hydrogen promotes pitting initiation and accelerates pit growth,thus enhancing the adsorption of chloride ions on the passivation film.Applied potential and chloride ions together promote the hydrogen permeability of the reinforcing steel.The IPZ model fails to consider the effect of the Heyrovsky mechanism on the hydrogen evolution reaction,and the linear relationship in the expression cannot be strictly established.With the negative shift of applied potential,the plasticity and strength loss of the reinforcing steel occur.When applied potential is-1.05 V,-1.20 V,the fracture mode of the reinforcing steel is brittle cleavage.The ductile-brittle transition occurs at-0.95 V,and the fracture morphology is delaminated.Applied potential of reinforced concrete structures in the actual marine environment should not be less than-0.95 V,otherwise the material is prone to brittle fracture.