Critical chloride threshold values as a function of cement type and steel surface condition

Purpose The purpose of this study is to investigate the inhibition efficiency and mechanism of a specific carboxylate corrosion inhibitor which consists of benzoic acid and dimethylethanolamine on steel surface. Design/methodology/approach The performance of carbon steel influenced by this organic inhibitor under different concentration of Cl− and immersion time was studied by linear polarization resistance and electrochemical impedance spectroscopy in a simulated concrete pore (SCP) solution. The surface morphology and composition of steel was also analyzed by optical microscopy, SEM and EDS to investigate the effect of inhibitor on the pattern of the steel surface after long-term immersion. Findings Carboxylate of benzoic acid and dimethylethanolamine can increase the chloride threshold level and decrease the corrosion area of carbon steel in SCP solution with 0.6 mol/L Cl− even after 120 days exposure. The inhibition mechanism of inhibitor lies in quick adsorption and buffering effect at initial time then formed deposited layer on steel surface after long-term immersion in chloride-rich environment. Originality/value It demonstrated that the carboxylate corrosion inhibitor not only can improve the chloride threshold level for carbon steel but also effectively decrease the corrosion rate even in chloride-rich SCP solution after long-term immersion, which is different form the conventional amino alcohol.

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A discussion of the paper “Chloride threshold values to depassivate reinforcing bars embedded in a standardized OPC mortar” by C. Alonso, C. Andrade, M. Castellote, and P. Castro

Cement and Concrete Research ◽

10.1016/s0008-8846(01)00485-9 ◽

2001 ◽

Vol 31 (5) ◽

pp. 835-838 ◽

Cited By ~ 11

Author(s):

T.U Mohammed ◽

H Hamada

Keyword(s):

Threshold Values ◽

Reinforcing Bars ◽

Chloride Threshold

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Influencing Parameters Analysis of Chloride Threshold Value on Reinforcements Embedded in Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.250-253.202 ◽

2011 ◽

Vol 250-253 ◽

pp. 202-206 ◽

Cited By ~ 3

Author(s):

Wei Qun Cao ◽

Xiao Mei Wan ◽

Tie Jun Zhao

Keyword(s):

Corrosion Potential ◽

Threshold Value ◽

Corrosion Current ◽

Visual Observation ◽

Cement Type ◽

Surface Conditions ◽

Chloride Threshold ◽

Type C ◽

Parameters Analysis ◽

Definition Of

The chloride threshold to develop active corrosion of the reinforcing steel does not seem to be a unique value and it depends on several factors, such as concrete mix proportions, cement type, C3A content of cement, blended materials, water/cement ratio, temperature, relative humidity, steel surface conditions and source of chloride penetration among others. Numerous studies have been already devoted to the study of the chloride threshold value for depassivation of the steel embedded in concrete. One of the reasons found for the scatter is the large number of variables that influence the chloride amount for depassivation. The other reason is the lack of accordance for the definition of the chloride threshold itself, either on the determining parameters (visual observation, corrosion potential or corrosion current) or on the expression of the threshold (as[Cl-]/[OH-] ratio or by weight of cement or concrete). The present paper presents chloride thresholds expressed as total, free and [Cl-]/[OH-] ratio.

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