THE INHIBITIVE effect of theophylline anhydrous on aluminum corrosion in hydrochloric acid solution was investigated using chemical and electrochemical techniques. It was found that the compound acts as good corrosion inhibitor with inhibition efficiency more than 99.9%. The inhibition efficiency was found to increase with inhibitor concentration and exposure time. On the other hand, it decreases by rising the temperature. The inhibition action was discussed in view of adsorption of the organic compound molecules on the aluminum surface. It was found that the adsorption of theophylline anhydrous on aluminum surface follows Langmuir adsorption isotherm. The thermodynamic parameters for the corrosion process in free and inhibited media were calculated and interpreted.

Celery (Apium graveolens) was used as natural corrosion inhibitor of carbon steel in 1.0 M HCl. The results of weight loss method and polarization showed that the inhibition efficiency was increased by increasing the Celery (Apium graveolens) inhibitor doses and reached the maximum at 500 ppm. The inhibition action of the extract was discussed in view of Temkin adsorption isotherm. It was found that the adsorption of the extract on Carbon steel surface is a spontaneous process. The effect of temperature on the IE% was studied; the IE% was decreased with increased temperature. Also, it was found that the presence of extract increases the activation energy of the corrosion reaction. Furthermore, the thermodynamic parameters of the adsorption process were calculated.

The inhibitive effect of polymeric surfactants on the corrosion of carbon steel in 0.5M HCl has been investigated by weight loss and polarization techniques.Potentiodynamic polarization measurements showed that these compounds are mixed type inhibitors.The adsorption of these inhibitors on carbon steel surface obeys Langmuir adsorption isotherm.The effect of temperature on the corrosion behavior of carbon steel in hydrochloric acid in presence of the most effective concentrations of the inhibitors was studied in temperature range (25 -70°C).The associated activation energy of carbon steel corrosion as well as energy of adsorption of studied compounds has been determined.

The inhibitive effect of Thevetia peruviana on the corrosion behavior of carbon steel in 1 M HCl was studied using the weight loss method, polarization, AC electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. The inhibition efficiency was found to depend on the concentration of the extract and the temperature of the medium. Results showed that this extract acts as a mixed-type inhibitor. The charge transfer resistance increases but the double layer capacitance decreases by increasing the extract concentration. It was found that the investigated extract acts via adsorption on the carbon steel surface and obeys the Temkin adsorption isotherm. The effect of temperature on the corrosion rate in the absence and presence of the extract was investigated, some activated, and the adsorption parameters were calculated. The results of the electrochemical methods were in good agreement with the weight loss measurement results.

ETYLTRIMETHYL ammonium bromide (CTAB) was investigated …….as corrosion inhibitors of mild steel in 0.1 and 0.5 M HCl solutions using weight loss, Tafel polarization and electrochemical impedance spectroscopy techniques.The experimental results showed that the inhibition efficiency increases with increasing of CTAB concentrations but decreases with increasing temperature.The adsorption of CTAB on the mild steel surface obeyed the Langmuir adsorption isotherm.Potentiodynamic polarization curves showed that CTAB acted as a cathodic inhibition predominantly in hydrochloric acid.This was supported by the impedance measurements which showed a change in the charge transfer resistance (R ct ) and double layer capacitance (C dl ) indicating adsorption of CTAB on the mild steel surface.Thermodynamic parameters were also calculated to know the mechanism of the inhibition.The thermodynamic functions of the adsorption processes were calculated from the weight loss and effect of temperature data and were used to analyze the inhibitor adsorption mechanism.The thermodynamic parameters indicate that physical adsorption and chemisorptions of the inhibitor on the metal surface may occur.

The corrosion inhibition of C-steel in 1 M HCl solution by cyanoacetamide derivatives was investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The results obtained from these techniques show that, the inhibition efficiency of these inhibitors increased with increase in inhibitor concentration but deceased with rise in temperature. Adsorption of these derivatives follows the Temkin adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed-type inhibitors for both anodic and cathodic reactions. Some activated thermodynamic parameters were computed and discussed. The results obtained from the four different techniques were in good agreement. Quantum structure-activity relationships have been used to study the effect of molecular structure on inhibition efficiency of the inhibitors.

The effect of Achillea fragrantissima on the corrosion of zinc in 0.5 M HCl has been studied using weight loss, hydrogen evolution and polarization measurements. The inhibition efficiency was found to increase with increasing concentration and decrease with increasing temperature. Inhibition effect was explained on the basis of adsorption of Achillea fragrantissima components on the metal surface through the active centers contained in their structures. It was found also that adsorption of Achillea fragrantissima on zinc surface follows Langmuir adsorption isotherm. Thermodynamic and kinetic parameters for zinc corrosion and inhibition processes were calculated and interpreted.

The effect of 2-amino-4,6-dihydroxy pyrimidine (ADHP) on the corrosion of carbon steel in 1 M HCl has been studied using weight loss and galvanostatic polarization measurements. The percentage inhibition efficiency was found to increase with increasing concentration of the inhibitor, and with decreasing temperature. The inhibitive effect of these compounds was explained on the basis of the formation of an insoluble complex adsorbed on the metal surface. The adsorption process follows Langmuir adsorption isotherm. The effect of temperature on the rate of the corrosion in the absence and presence of these compounds was also, studied. The activated thermodynamic parameters were calculated and explained.

Inhibition of corrosion of aluminium in 0.5 M HCl solution using polyethylene glycol compounds (PEG with different molecular weight, 600, 2000, 6000 g mol) has been studied using weight loss measurements, glvanostatic,and potentiodynamic anodic polarization techniques. The results drawn from these techniques are comparable and exhibit small discrepancy. The percentage of inhibition efficiency was found to increase with increasing the concentration of inhibitors and the decrease of temperature. The inhibiting action of these compounds depends on the chemical structure, the concentration of the inhibitors, and the temperature. The efficiency of inhibition increases in the order: PEG600 <PEG2000 < PEG6000 in the studied concentration range. Inhibition is attributed to the adsorption of these compounds on the aluminium surface. The adsorption process fitting a Temkin adsorption isotherm. It was found that PEG compounds protect aluminum surface pitting attack in chloride containing solution by shifting the pitting corrosion potential to more noble direction. [M. Abdallah, H.E. Megahed, M. A. Radwan and E. Abdfattah. Polyethylene Glycol Compounds As Corrosion Inhibitors for Aluminium in 0.5M Hydrochloric Acid Solution. J Am Sci 2012;8(11):49-55]. (ISSN: 1545-1003). http://www.jofamericanscience.org. 7

The effect of five compounds of ethoxylated fatty esters with different number of ethylene oxide units on the corrosion of copper in 1 M HNO3 solution has been studied using weight loss and galvanostatic polarization techniques. The inhibition efficiency was found to increase with increasing concentration and number of ethylene oxide units per molecule. Inhibition effect was explained on the basis of adsorption of ethoxylated fatty esters on the metal surface through their ethoxy groups. The adsorption process was found to follow Temkin adsorption isotherm. Polarization data suggested that the used additives act as mixed type inhibitors. It was found also that the ethoxylated fatty esters provide a good protection to copper against pitting corrosion in chloride containing solutions.

The effect of Ni2+ cation, imidazole, and mixtures of them on the corrosion behavior of carbon steel in 0.5 M H2SO4 solution was studied by using galvanostatic polarization, potentiodynamic anodic polarization, and weight-loss techniques. Ni2+ cation, imidazole, and mixtures of them provide a good protection to carbon steel against pitting corrosion in chloride-containing solutions. The inhibiting solutions were analyzed by using UV–Vis spectrophotometry. The inhibition was explained on the basis of formation of a complex between the two components. The inhibition mechanism was discussed in terms of the results derived from corrosion and UV–Vis spectrophotometric measurements as well as conductometric investigations.

Pitting corrosion of nickel and its alloys (Inconel 600 and Incoloy 800) in 0.1 M H2SO4 solution containing of NaCl was studied using cyclic voltammetry and potentiodynamic anodic polarization techniques. The integrated charge amounts Deltaq(a) in presence of Cl- ions was taken as a measure of pitting corrosion. The pitting potential was varied with Cl- ion concentrations according to an S-shaped curves. Addition of dihydrazide derivatives of malonic, succinic and adipic acid caused a shift of pitting potential in the noble direction accounting for increased resistance to pitting attack.

The electrochemical behaviour of Fe and C-steel samples in oxalic acid solutions was studied by the use of cyclic voltammetry. Two peaks were observed; the first one was the anodic peak and the second one an unexpected reductive dissolution peak which could be observed in the cathodic branch of cyclic voltammograms of all electrodes studied. The carbon content was found to increase the active dissolution of steels and to decrease their tendency towards passivation. The inhibitive efficiency of phenyl phthalimide derivatives on the active dissolution of Fe and steel samples in 0.1M oxalic acid were investigated.

New CuII, CoII, NiII, CdII, ZnII, HgII, PdII and UO 2 II complexes of the Schiff base ligand (FBz) formed by condensation of fluorenone withS-benzyldithiocarbazate have been prepared and characterized by elemental analysis, magnetic and spectroscopic measurements. The Cu(FBz)2(Cl)2 complex is paramagnetic. The Ni(FBz-H)2 complex is diamagnetic, four-coordinate and square planar. The CoII ion is oxidized in the presence of the Schiff base with the concomitant formation of CoIII complex of empirical formulae Co(FBz)Cl3OH2. The ligand was tested as a corrosion inhibitor for copper. Inhibition efficiency was calculated and the limiting concentration of FBz to give maximum efficiency was 10−3 mol dm−3 at 25°C. The polarographic reduction of FBz was investigated in Britton-Robinson buffer solutions of pH 3–10. The polarograms at dme indicated that the depolarizer is reduced through two two-electron irreversible diffusion-controlled waves. The mechanistic pathway of the electrode reaction is commensurate with this result.