الفهرس 
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Abstract
Corrosion can cause serious failures, which lead to large economic loss,
sometimes combined with environmental pollution, or risk of personnel
injuries. The most important steps in order to hinder or reduce the extent of
such failures are sufficiently early detection, proper diagnosis and effective
prevention measures.
Among numerous inhibitors that have been tested and applied
industrially as corrosion inhibitors, those that are non-toxic or low-toxic are
now far more strategic than in the recent past. In the twenty-first century, the
research in the field of “green” or eco-friendly corrosion inhibitors has been
addressed towards the goal of using cheap effective compounds at low or zero
environmental impact. Research on green inhibitors is of considerable
interest in investigations into the replacement of hazardous classical
molecules.
In the present investigation on “Inhibitive action of Valerian
officinals, Chenopodium ambrosiodes, Hierochuntica Anastatica , Melissa
officinalis on the corrosion of carbon steel in acidic media and their
adsorption characteristics” has been undertaken and the results pertaining to
the current study is discussed in detail in chapter III.
Efforts have been taken to study the inhibitive action of Valerian
officinals, Chenopodium ambrosiodes, Hierochuntica Anastatica and
Melissa officinalis extracts in 2 M HCl solution by mass loss and
electrochemical polarization techniques. Studies were carried out at various
concentrations of the aqueous extracts at different times of immersion at room
temperature by mass loss method. Effect of temperature was also studied to
evaluate the kinetic and thermodynamic parameters. Various adsorption
isotherms were also fit for the adsorption of the studied extracts on carbon
steel surface. The electrochemical technique (Tafel intercept method) method
was adopted to understand the mechanism of inhibition. Efforts have also
been to suggest a suitable mechanism for carbon steel corrosion.
The thesis contains three chapters:
Chapter (I) is concerned with an introduction about the carbon steel
metal, its occurrence, its electrochemical reactions in aqueous
solutions, theories of corrosion, types of corrosion inhibitors and the
usage of naturally occurrence substances as corrosion inhibitors.
Moreover, the chapter contains a literature survey of the previous
works have been conducted in using of the naturally, organic and in
organic occurring substances in inhibition of carbon steel.
Chapter (II) deals with experimental part, which includes a description
of the used plants and the method of preparing the investigated extracts.
Experimental techniques, including the full description of the used
instruments and detailed procedures used for determination of the
corrosion rate and inhibition efficiencies of the used extracts.
Chapter (III) contains the results obtained from the different used
techniques as well as the interpretation of these results in view of the
theories of corrosion thermodynamics and kinetics. Moreover, a
proposed mechanism was given at the end of the chapter based on the
obtained results.