Electrochemistry of Reinforcing Steel in Salt-Contaminated Concrete

Abstract

Corrosion rates of reinforcing steel have been measured in concrete using the polarization resistance technique. The corrosion rates have been calculated for seven different sodium chloride content and two different surface conditions of steel in concrete. The results from partially coated reinforcing steel specimens indicate the existence of a critical sodium chloride concentration between 0.1 and 0.2 percent by weight of concrete at which the rate of corrosion increases significantly. Anodic and cathodic Tafel slopes have also been determined experimentally. The high values of Tafel slopes may be attributed in part to IR drop; however, more research is needed to clarify this matter.

Chloride-induced corrosion of reinforcement in low-calcium fly ash-based geopolymer concrete

“…Average B constants were ranging from 82 to 278 depending on the sodium chloride content of the concrete, which are much higher than the proposed 52 and 26 for passive and active samples respectively [63]. Locke and Siman argued that the higher observed Tafel slopes are in part due to IR-drop, which was not compensated [66]. The amplifying effect of uncompensated IR-drop on the Tafel slopes of the polarization curve is theoretically discussed in detail in [67]; Although, it is of course insignificant for very low electrolyte resistances [68].…”

“…Locke and Siman [66] investigated the effect of sodium chloride concentration on corrosion rate and Tafel constants of reinforced concrete samples. Average B constants were ranging from 82 to 278 depending on the sodium chloride content of the concrete, which are much higher than the proposed 52 and 26 for passive and active samples respectively [63].…”

“…These parameters can be listed as: the conductivity of the electrolyte [68] which depends on the moisture content and presence of various ions in the electrolyte, the presence and concentration of chloride ions [66], pH of the electrolyte that can be affected by the carbonation or chemical composition of the electrolyte [70], the polarization mechanism (i.e. activation polarization or concentration polarization) which depends on the availability of the ions involved in redox reactions [65,71], dependency of the Tafel constants on the corrosion potential which varies with time [43,72], the presence of surface films or the mill scale covering the surface of the reinforcement and the surface preparation method [66,73], and pore structure of the concrete which influences the transport properties of different species within the concrete medium. Although chemical composition of the binder (electrolyte) is only one of the many parameters which affect the corrosion kinetic, the polarization curve, and hence the Tafel slopes, given the distinct lack of data on Geopolymer-based corroding systems, measuring the Tafel constants seems to be a necessary step toward developing a database which can be used further in the non-destructive LPR test method.…”

Corrosion of steel reinforcement in concrete of different compressive strengths

“…They reported that the calculated corrosion rate was in the range of 0.20-2.5 mpy. Locke and Simon [22] found for concrete mixed with 0-1% NaCl, the estimated corrosion rate based on linear polarization resistance technique was in the range of 0.03-0.52 mpy. Wheat and Eliezer [23] used potentiodynamic polarization technique for corrosion rate measurements of steel in concrete specimens immersed in 10% NaCl solution for 30 and 150 days.…”

Measuring the corrosion rate of reinforcing steel concrete - final report

“…An early review of the literature revealed a dearth of information in this area (9). A means of measuring the corrosion rate of steel in concrete would be extremely useful for many applications, and several laboratories, including the National Bureau of Standards (NBS), have devoted time to developing some understanding of how this measurement can be made in a nondestructive manner (10)(11)(12).…”