Green Plant Extract as a passivation- promoting Inhibitor for Reinforced Concrete Abdulrahman A. S. Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM/ Mechanical Engineering Department, Federal University of Technology Minna, Nigeria asipita68@yahoo.com Mohammad Ismail Faculty of Civil Engineering Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia mohammad@utm.my ABSTRACT The present corrosion inhibitors in market for the protection of steel reinforcement in concrete exposed to chloride attack are toxic to the environment and compromises sustainability drives. There is the needs to develop inhibitor that are eco-friendly and sustainable. In this work the ability of hydrophobic green plant extracts inhibitor (Bambusa arundinacea) to repassivates the chloride induced corrosion of steel was studied. Its efficacy and effectiveness was also compared with calcium nitrite inhibitor. Concrete mix was designed to 30MPa with 0.45 W/C ratios and 1.5% weight of cement content of chloride was added to initiate corrosion. Inhibitors additions were 2%. Electrochemical impedance spectroscopy, linear polarization resistance and Field emission spectroscopy (FESEM) were used to monitor corrosion behavior of steel at 180 days exposure period. Corrosion rate of the inhibitors studied showed that Bambusa Arundinacea is superior as compared to calcium nitrite as results of its high concrete resistivity, chloride binding property and polarization resistance. Bambusa Arundinacea may be considered a better substitute for nitrite based corrosion inhibiting admixtures for durable concrete structures due its versatility. Keywords: Concrete; Chloride attack; Green plant extracts; Inhibitors; Carbon Steel Introduction Reinforcement steel in concrete normally acquires a permanent state of passivity due to the high alkalinity of the environment (Abd El Haleem et al. 2010a). pH values higher than 12 result from the liberation of Ca(OH) 2 and the presence of potassium and sodium hydroxides ensuring continuous protection of the steel (Abd El Haleem et al. 2010b; Abd El Haleem et al. 2010c). Presence of oxygen stabilizes the passive film on the surface of the embedded steel. Although the precise nature of the passive film is unknown, several views have been advanced in this context. A spinel α-Fe 3 O 4 –γ-Fe 2 O 3 solid solution is proposed to form the passive film on steel (Batis and Rakanta 2005; Ann et al. 2010; Balafas and Burgoyne 2010). However, Contamination of concrete with ions like Cl - causes breakdown of passivity and initiation of localized attack (El Hassan et al. 2010). Chloride ions can enter the concrete from de-icing salts, from sea water in marine environments, from chloride containing admixtures and/or from mixing water (Alvarez et al. 2011). Above a certain threshold chloride ion concentration, the passive layer on the reinforcing steel breaks down as a result of chloride induced pitting of steel (Berke 2005; Blau et al. 2007; Apostolopoulos and Koutsoukos 2008). Over the years a number of protection measures have been suggested by many workers to delay, slow, or stop the corrosion process, thereby enhancing the service life of concrete structures. One of the practical methods suggested for the control of steel corrosion in concrete is the use of corrosion inhibitors either preventive or curative treatment (Trépanier et al. 2001; Tritthart 2003; Martínez and C. Andrade 2008; Tittarelli and Moriconi G. 2008; Tao et al. 2009; Tommaselli et al. 2009; Vedalakshmi et al. 2009; Yuan et al. 2009; Zhang et al. 2009; Zhang et al. 2009; Jing and Wu 2011). Abdulrahman A. S. et al. / International Journal of Engineering Science and Technology (IJEST) ISSN : 0975-5462 Vol. 3 No. 8 August 2011 6484