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تثبيط تاكل الحديد الكاربوني الواطئ في حامض الكبريتيك باستعمال كحول البولي فينيل ومستخلص نبات PIPER LONGUM == Corrosion Inhibition of Low Carbon Steel In Sulfuric Acid By PVA And Piper Longum Extracts
Author name:
اياد بهاء الدين احمد
Supervisor name:
ماجد ابراهيم عبد الوهاب | ابرائيل سركيس يارو
General topic:
Chemical Engineering
Specific topic:
Chemical Engineering
Degree:
Doctorate
University:
University of Baghdad - College Of Engineering - Department Of Chemical Engineering
Language:
English
University location:
Baghdad
First pages:
38T269 - p.pdf
Abstract:
The inhibitive power of Polyvinyl Alcohol (PVA) and the synergistic effects added on the inhibition power of PVA by two types of Piper Longum (PL) Ethanol Extracts (PLEXT) were investigated toward the corrosion of carbon steel in (0.2N) H2SO4 solution in the temperature range (30 - 60?C) and PVA concentration range (150 - 2000 PPM).The corrosion rate measurements were carried out using the following two standard corrosion measurements techniques.1. Weight loss technique was applied on carbon steel plates to evaluate inhibition efficiency in presence and absence of these inhibitors.2. Electrochemical Techniques were used to validate and support inhibition efficiencies found in weight loss techniques.A detailed study of the experimental methods and results is reported for each test conducted.The weight loss results showed that PVA could serve as a corrosion inhibitor but its inhibition power was found to be low for the corrosion of carbon steel in the acidic media.It was shown that the inhibition efficiency for (PVA) decreased with increasing temperature at a given PVA concentration. On the other hand it was shown that at given temperature the inhibition efficiency of (PVA) was increased with increasing of PVA concentration until a PVA concentration of 2000 ppm PVA was reached then only a slight decrease in inhibition efficiency was observed when increasing PVA concentration further.The Maximum inhibition efficiency reached was about 71 % at 30?C & 2000 ppm (PVA) concentration, calculated by the weight loss techniques.In order to improve the inhibition efficiency of PVA, by adding 6 ml/l of ethanol extracts of piper longum (PL) to a liter of the acid solution in presence of concentrations of PVA 150,500,1000.1500, and 2000 ppm at temperatures (30,40,50, and 60?C) was investigated.Weight loss results showed a jump in inhibition efficiency (% IE) value of the modified inhibitor mixture compared with the presence of PVA alone at all (PVA) concentrations for temperature range considered in this investigation.This study demonstrated the extra inhibition power added by the (PL) fruit extracts to the organic polymer (PVA) used. Maximum inhibition efficiencies recorded were approximately 95% for Piper Longum Extract Number two (PLEXT2) at 30?C and 2000 ppm PVA.The kinetic and thermodynamic parameters regarding the adsorption process of inhibitors used was calculated.It was found that the changes corrosion rates correlates well with the Arrhenius equation in absence and presence of inhibitors.The Results showed that the adsorption of the polymer and the plant extract follows Langmuir adsorption isotherms and the adsorption of the inhibitor molecules on the metal surface is mainly physical, nevertheless the adsorption is believed to be slightly deviated from the Langmuir model at 30?C.Electrochemical analysis of the corrosion process of carbon steel in an electrochemical corrosion cell was investigated using 3 - Electrode corrosion cell coupled with a potentiostat interfaced with a computer which assisted polarization data interception and interpretation.Polarization technique was used to obtain polarization data which was recorded for carbon steel in 0.2N H2SO4 solutions in presence and absence of the inhibitors investigated. Electrochemical runs were done in the (PVA) concentrations of 150, 1000, and 2000 PPM and a temperatures of 30, 40, 50, and 60?C.Tafel slopes, Corrosion currents, and corrosion rates were calculated from polarization curves by Tafel extrapolation method. Results showed corrosion rate trends similar to findings by the weight loss method. It was indicated also that the corrosion of carbon steel in 0.2N H2SO4 is highly activity controlled.Results revealed that the inhibition action is occurring at both anodic and cathodic sites on the metal surface so that both corrosion reactions were affected, so that the composite inhibitor could be considered as mixed - type inhibitor.Electrochemical results confirmed that (PLEXT2) was more efficient as inhibition improvement additive to (PVA) than (PLEXT1) at all experimental conditions range encountered in this study.The highest inhibition efficiency recorded using Tafel polarization method was 83% obtained at 30?C and 2000 ppm of PVA with 6 ml/l PLEXT2.
