A potentiostatic study of the behaviour of Inconel (600) in molar sulphuric acid has been carried out over the temperature range 293-313 K. Values have been established for the potentials and current densities of the corrosion, active-passive transition, passivity and transpassive states. For corrosion, the current density (ic) and potential (Ec) have been determined from well-defined Tafel lines. The potential and current density prior to the commencement of passivity have been obtained corresponding respectively to the critical potential (Ecr( and to the current density (icr) for the active-passive transition state. The passive range was defined by the respective potentials and current densities for passive film formation and dissolution. The dissolution point was correlated with transpassive potential (Et) and current density (it). All the estimated potentials and current densities for the various states were influenced by temperature and the presence of additives in the sulphuric acid. Additives such as nitric acid, thiourea and sodium chloride lowered the corrosion current density (ic) of the alloy while hydrochloric acid enhanced the value of ic. Addition of thiourea or sodium chloride or hydrochloric acid caused a shift in the corrosion potential (Ec) to less negative values while nitric acid shifted Ec to more negative potentials. The kinetic effect of the additives have been studies. Values of activation energy (E) were considered to be apparent and some negative values of E have been obtained with certain additives for the critical and passivity processes. Such negative E values were attributed to small values of true energies of activation together with relatively large exothermic enthalpies of such processes.
In this work, corrosion parameters were evaluated using potentiodynamic polarization curves. In order to determine corrosion parameters of potential and current density of the interesting metal, carbon steel, environmental conditions of external corrosion of buried carbon steel pipeline in Iraqi soil were prepared in the laboratory using simulated prepared conditions. Solutions of sodium chloride at different concentrations (300, 1100, 1900, 2700, and 3500 ppm) were used. pH of solution were acidic at pH =5, and alkaline at pH = 9. Laboratory conditions were similar to those of Iraqi soil where the pipelines were buried. Temperature was constant at 20 °C. Potentiodynamic polarization curves, of potential vs. log current density, were ob
... Show MoreRotating cylinder electrode (RCE) is used . in weight loss technique , the salinity is 200000 p.p.m, temperatures are (30,5060,7080Co) . the velocity of (RCE) are (500,1500,3000 r.p.m). the water cut (30% , 50%). The corrosion rate of carbon steel increase with increasing rotating cylinder velocity. In single phase flow, an increase im rotational velocity from 500 to 1500 r.p.m, the corrosion rate increase from 6.88258 mm/y to 10.11563 mm/y respectively.
In multiphase flow, an increase in (RCE) from 500 to 1500 r.p.m leads to increase in corrosion rate from 0.786153 to 0.910327 mm/y respectively. Increasing brine concentration leads to increase in corrosion rate at water cut 30%.
Corrosion inhibiting admixtures are unique among other methods to protect reinforced concrete from corrosion damage. In this study, the effect of furfural on the fresh and hardened properties of concrete mixes of 35 and 45 MPa compressive strengths as well as the corrosion inhibition of furfural was evaluated. Furfural was added at different dosages (1, 2 and 3% by weight of cement) with and without superplasticizer (HRWR). Different electrochemical measurements were performed (Half-cell potential, Tafel plot and linear polarization resistance). Electrochemical measurements confirmed that furfural dramatically reduces the rate of corrosion; the inhibition efficiencies were 62.7 and 63.8 % due to 3% furfural addition to 35 and 45MPa-concr
... Show MoreThis work includes preparation of Az, Qz, and Tz derivatives from the reaction of Schiff base (Sb) derivative with anthranilic acid, chloroacetyl chloride, and sodium azide, as well as, the characterization via FT-IR, 1H-NMR, and 13CNMR. The anticorrosion inhibition of these compounds was studied and the measurements of carbon steel (CS) corrosion in sodium chloride solution 3.5% (blank) and inhibitor in solutions were calculated at a temperature range of 293-323 K by the technique of electrochemical polarization. In addition, some thermodynamic and kinetic activation parameters for inhibitor and blank solutions (Ea⋇, ΔH⋇, ΔS⋇, and ΔG⋇) were determined. The results showed high inhibition efficacy for all the prepared compounds,
... Show MoreThe inhibitive effect of imidazol on the dissolution of Zn in (1M) HCl has been studied. The inhibion effect of imidazol ,protection efficiency and the corrosion rate of Zn in (1M) HCl were investigated at various concentrations (1x 10-3 – 5x10-3) M and tempearture range (285-328) K. The corrosion inhibitive of Zn by imidazol was studied using weight loss measurement and analytical titration of the amounts of dissolved zinc in acidic solution in presence and absent of imidazol. It was observed that imidazol led to protection efficiency reached to (88.93)% when (10)mM imidazol concentration was used. A linear relationship came true between (C/?) and (C); where (?) is the coverage of Zn surface by imidazol which could be obtained from
... Show MoreThe corrosion of low carbon steel boiler tubes in demi water had been investigated. The purpose of this investigation was to determine the change produced in corrosion behavior of the carbon steel as a result of the specific presence of chloride and copper ions in the water under different temperatures. For low carbon steel experiments, the temperature was taken in three levels (125, 175, and 215°C) under about 27 bar pressure and 1500 rpm in autoclave. Using weight loss technique, the corrosion rate ranges from (85 to 789 gmd) for low carbon steel boiler tubes.
The effect of mixed corrosion inhibitors in cooling system was evaluated by using carbon steel specimens and weight loss analysis. The carbon steel specimens immersed in mixture of sodium phosphate (Na2 HPO4) used as corrosion inhibitor and sodium glocunate (C6 H11 NaO7) as a scale dispersant at different concentrations (20,40, 60, 80 ppm) and at different temperature (25,50,75 and 100)ºC for (1-5) days. The corrosion inhibitors efficiency was calculated by using uninhibited and inhibited water to give 98.1%. The result of these investigations indicate that the corrosion rate decreases with the increase the corrosion inhibitors concentration at 80 ppm and at 100ºC for 5 days, (i.e,
... Show MoreAbstract
Stainless steel (AISI 304) has good electrical and thermal conductivities, good corrosion resistance at ambient temperature, apart from these it is cheap and abundantly available; but has good mechanical properties such as hardness. To improve the hardness and corrosion resistance of stainless steel its surface can be modified by developing nanocomposite coatings applied on its surface. The main objective of this paper is to study effect of electroco-deposition method on microhardness and corrosion resistance of stainless steel, and to analyze effect of nanoparticles (Al2O3, ZrO2 , and SiC) on properties of composite coatings. I
... Show MoreThe present study was conducted to evaluate the effect of different inhibitors on the corrosion rate of aluminum in 50% (v/v) ethylene glycol solution at 80°C and pH 8.0 in which the electrochemical technique of linear sweep voltammetry was employed to characterize each inhibitor function and to calculate the corrosion rate from Tafel plots generated by a computer assisted potentiostat.
It is found that both sodium dichromate and borax reduces the corrosion rate by polarizing the anodic polarization curve while sodium phosphate, potassium phosphate, and sodium benzoate reduces the corrosion rate by polarizing both the anodic and cathodic polarization curve.
When inhibitor concentration increases from I g/l up
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