During the last decade, the use of several kinds of inhibitors has increased significantly. However, it is needed to ensure the long-term inhibiting capacity of the substance.

This paper presents the results of the exposure of concrete specimens containing ZnO and ZnO/Ca(NO2)2 as inhibitors to an aggressive marine environment after more than three years. The inhibiting capacity results will be described based on electrochemical measurements. Besides, a possible mechanism of ZnO action will be given.

To study the effect of these inhibitors, 244 specimens were prepared with tap water and water from lake Maracaibo (≅ 3000 ppm Cl-), and exposed to saline environment for more than three years. Water/cement ratios 0.45, 0.5 and 0.6 were used, with inhibitor concentrations of 2 %, 3 % and 4 % of ZnO or Ca(NO2)2, and a mixture of both at 2 %, concentration on cement weight basis.

All the results (physic-chemical and electrochemical), indicate that ZnO and its mixture with Ca(NO2)2 show better performance than Ca(NO2)2. In spite of the higher corrosion rates (icorr > 0,1 μA/cm2) of the ZnO specimens (w/c = 0.45), the potentials values (E > -200 mV vs Cu/CuSO4) and the cyclic polarization curves show passivation of the steel after more than two years of exposure to the aggressive environment.

Cyclic voltammetric method at 200 mV/s for studying the inhibiting effect of these substances is described. Pore solution and pure iron were used as the electrolyte and working electrode, respectively. The results show that there are not differences in the passive film formed in pore solution with and without the inhibitors.

Subject
Water, Rebar, Passive films, Iron, Mixtures, Pores, Zinc oxide, Specimen preparation, Corrosion inhibitors, Steel, Chlorides, Corrosion potential, Concrete
Keywords:
Corrosion, Reinforced Concrete, Inhibitors, Zinc Oxide, Calcium Nitrite
© 2003 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2003
Association for Materials Protection and Performance (AMPP)
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