Corrosion Behavior Of Typical Stainless Steels In The Concrete Under Marine Environment

The high alkaline environment provided by concrete pole solution in reinforced concrete structure can protect the rebar.However,in the marine environment,chloride ions can rapidly enrich to a very high level due to the intrusion and transpiration.Under the high chloride ion concentration solutions,carbon steel cannot remain passivated,thus causing corrosion.The volume expansion caused by the corrosion products will destroy the concrete and accelerate the failure of the components.Stainless steel can greatly improve the stability of passive film,resist chloride ion erosion and greatly extend the life of the components.In this paper,the cyclic polarization curve,electrochemical impedance spectrum,Mott-Schottky,X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),Energy Dispersive Spectrometer(EDS)and other techniques were used in passivation and corrosion behavior of some grades of stainless steel in simulated marine environment concrete.The research showed that the corrosion resistance of stainless steel decreases with the increase of chloride ion concentration and the decrease of alkalinity.The relationship of corrosion resistance among the stainless steels were 2507 > 2205 > 2304 > 316 L > 304 SS > 301 SS,which is in same with the relationship of the pitting resistance equivalent numbers(PREN).According to the XPS analysis,the content of the passive film formed in the solutions of higher pH value has higher Cr ratio and lower Fe ratio.Studies on inclusions in 2304 stainless steel showed that in alkaline environments,alumina was dissolved and(MgAl)-oxides did not.This result in the sensitivity of alumina inclusions to the alkaline environment and the higher sensitivity of the(MgAl)-oxides to the neutral environment.The corrosion resistance of stainless steel with alumina inclusions was reduced with the rise of the solution alkalinity.The carbonation process of real stainless steel concrete system was studied.Research showed that the concrete has a good protection effect to the stainless steel.The corrosion of stainless steel will not occur before completely carbonization process.The relationship between electrode potential and corrosion behavior was constructed based on several experiments.The method of on-line inspection of stainless steel concrete structure was proposed.