| At present, damage of durability of concrete structures which induced by steelcorrosion has been a serious problem in all over the world. To solve this problem, aseries of protective measures have been studied, of which is the corrosion inhibitor.Due to its high efficiency and convenience, it is widely applied in practicalengineering. The primary cause of steel corrosion in marine environment is thepenetration of chloride. Taking the marine environmental issues into account, it hasbeen a research focus to study the property of steel corrosion inhibitor of highefficiency and low toxicity.In this paper, anticorrosion properties of three soluble vitamincompounds（ascorbic acid, nicotinic acid, pyridoxine） and two triazolecompounds（triadimefon, uniconazole） were studied by quantum chemicalstructure-activity relationship, the coulostatic method, electrochemical impedancespectroscopy （EIS） and potentiodynamic polarization curves.Quantum chemistry method was used to study the molecular optimism geometry,total charge density distribution and frontier molecule orbital density distributions ofthe selected compounds to obtain their advantages on structures as inhibitors. In3.5%NaCl solutions with different concentrations of corrosion inhibitor, the change ofcathode Tafel slope a, anode Tafel slope cand corrosion current density Icorrweremeasured by the coulostatic method to calculate the corrosion efficiency. The resultsshowed that if the concentrations of vitamin corrosion inhibitors reach the range of1.0×10-3mol/L～1.5×10-3mol/L, the corrosion current density decreases sharply andanticorrosion efficiency improves significantly. And if the concentrations of triazolecorrosion inhibitors reach the range of1.0×10-4mol/L～6.5×10-4mol/L, theanticorrosion efficiency becomes stable, the cathodic Tafel slope decreases slowly andbecomes constant in some interval. The efficiencies of corrosion inhibitors wereevaluated and predicted with combination of the coulostatic method and the quantum structure-activity relationship. The results showed that calculated corrosion efficiencyE Cal（%） and experimental corrosion efficiencyE exp（%） for vitamins and triazolecompounds are of good correspondence, and the correlation coefficient R=0.92929and R=0.97835respectively.The anticorrosion properties of inhibitors with different concentrations in3.5%NaCl solutions were measured by EIS. The results showed that when theconcentrations of the ascorbic acid and pyridoxine reach4.0×10-3mol/L, the radius ofcapacitance arc become the largest, which mean these inhibitors of this concentrationhas the greatest efficiency. Meanwhile, when the concentrations of triadimefon anduniconazole reach1.0×10-4mol/L, the anticorrosion efficiency becomes stable.The study of the durability of inhibitors was carried out by the method of acimpedance, the study showed that the selected five kinds of corrosion inhibitors havelong-lasting anticorrosion and the result showed that three vitamin compoundsimpedance spectroscopy capacitive reactance arc radius increased with the extensionof time in the first20d; the capacitive reactance arc radius of ascorbic acid andnicotinic acid still showed the trend of increase in45～65d. However, impedancespectroscopy capacitive reactance arc radius of pyridoxine obviously reduced;impedance spectroscopy capacitive reactance arc radius of triadimefon anduniconazole increased with the extension of time in the first20d; and still kept thetrend of increase and had high impedance modulus in45～65d, while impedancespectroscopy capacitive reactance arc radius of triadimefon reduced obviously.Anticorrosion efficiency of corrosion inhibitors at different temperatures weremeasured by EIS and potentiodynamic polarization test. The results show thatanticorrosion efficiency decreases with increasing temperature.The results of concrete by adding vitamin corrosion inhibitors find that corrosioninhibitor don’t affect mechanical properties of concretes, and increase the abilities ofcarbonization and chloride resistance to some extent. |
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