Research Article:

Ahmed Rajih Hassan, Eng. College, Chemical Eng.

Ali Khalil Ismael, Eng. College, Civil Eng.

Firas Naif Hassan, Eng. College, Chemical Eng.

E-mail addresses:  ah.ra3@yahoo.com, aly_khalil78@yahoo.com, Firas_nayfe@yahoo.com

ABSTRACT

Corrosion inhibitors studies were carried out on carbon steel rebar samples under different pH
conditionsand in the presence and absence of chloride ions in solution. A known amount of
sodium nitrite was added asan inhibitor and the mechanism of inhibition was studied by tracking
both the thermodynamic and kineticproperties of the system. The studies indicate thatInhibition
efficiency decreases with increase of temperature, and there is a competition between the
corrosion and passivationreactions, and the resulting open-circuit potential depends on the
relative strength of the corroding and passivatingenvironments. The corrosion rate depends to a
great extent on the pH of the solution. Nitrite ions act asanodic inhibitors by increasing the rate of
formation of a barrier oxide film. The protective action of the nitriteions seems to be more
pronounced in highly corroding environment. This is due to the mechanism of inhibition,which
uses the product of the unwanted corrosion reaction and converts it into a favorable passivating
one. Fora given amount of chloride, a minimum threshold concentration of nitrite is essential for
protecting the steel.

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