الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 136 |  |  |
| | | from | 136 | | |
Abstract
The aim of the present work is to study the corrosion behavior of carbon steel used in petroleum pipe lines in 0.5 M H2SO4 using carrageenan compounds namely, e.g (λ–carrageenan, i–carrageenan , K- carrageenan and monomer ) and also in 0.5 M NaOH using natural oils namely ,e.g (lettuce , radish and parsley) . The thesis comprises three main chapters :- Chapter 1:- This chapter deals with the introduction , which includes definition , classification of corrosion , corrosion inhibitors . literature survey on corrosion behavior of carbon steel in aqueous solutions . Chapter 2 :- Deals with the experimental part includes complete description of the working procedures, preparation of solutions, electrode treatment, electrolytic cell and electrochemical measurements . Chapter 3 :- In this part (A) potentiodynamic anodic polarization curves of carbon steel in 0.5 M H2SO4 solution containg different concentrations of NaCl solution and also, potentiodynamic anodic polarization curves of carbon steel in 0.5 M NaOH solution containg different concentrations of NaCl solution were studied. It was found that the addition Cl- ions cause the destruction of the passivation oxide film and initiate pitting corrosion. The pitting corrosion potential for these additives are shifted to more negative values with increasing chloride ion concentrations. Trials were made to inhibit the pitting corrosion of carbon steel by using carrageenan compounds in H2SO4 solution and also by using natural oils in NaOH solution. These compounds shifted the pitting potential to more positive values, indicating the inhibiting effect of these compound. Part (B): This part study the effect of addition of different concentrations of carrageenan compounds and some oils on the galvanostatic polarization curves of carbon steel in 0.5 M H2SO4 and 0.5 M NaOH, respectively. Some corrosion parameters were calculated such as corrosion potential (Ecorr) ,corrosion current density (Icorr), anodic (ba) and cathodic(bc) Tafel slopes. By increasing the concentrations of carrageenan compounds and natural oils The corrosion current density decrease and consequently the inhibition efficiency is increased. The adsorption isotherm for each carrageenan compounds and natural oils on the steel surface follow Langmuir adsorption isotherm at constant temperature. Part (C ): This part contains the results of the potentiodynamic anodic polarization curves of carbon steel in 0.5 M H2SO4 in absence and presence of some carrageenan compounds at scanning rate of 50 mV sec-1. Also, the effect of some natural oils towards the corrosion of carbon steel in 0.5 M NaOH was studied. These results indicated that: I)There is one anodic peak (A) due to the dissolution of iron. Ii)The values of peak anodic current decreases and consequently the inhibition efficiency increases indicating an increased resistance to corrosion. -Finally the mechanism of inhibition for the additives compounds was suggested . -This thesis contains also references , English and Arabic summaries.