Oxide Film Growth on Copper in Neutral Aqueous Solutions

The copper electrode potentials measured by the open circuit potential method in strongly aerated solutions of SO4-2, Cl-, Br-, I-, CrO4-2, CO3-2, and NO2- with difference concentrations, till steady state values are attained. The copper electrode potentials of the all experiments increase from negative to more positive values indicating oxide film growth. The copper oxide film thickness attains maximum value at low and high concentrations of each aggressive and inhibitive anions respectively. The rate of oxide film thickening is determined by use the relation: E = a + b log t, where a and b are constants. The concentration of the inhibitive anions, CrO4-2, CO3-2, and NO2- that can withstand a certain concentration of the aggressive ions, , Cl-, Br-, and I-, varies due to the relation: logC inh. = A + n logC agg., where A and n are constants. The all experiments were investigated at 25oC in all electrolytes. Keywords: Copper; oxide growth; passivity; open circuit potential

Simple N Compounds Electrochemical Behavior of Steel in Aqueous Solutions

Chemical polishing or electropolishing, instead of mechanical polishing, are recommended for the attainment of metallic surface polishes without the introduction of contaminates or tensions in the surface layers of the metal. The fundamental difference between the chemical and electropolishing processes is that in the latter anodic currents/potentials are used to help in the dissolution and passivation of the metal. The elctropolishing process inhibited with different ratio by addition of amide derivatives with concentration range 1x10-6 to 5x10-3M .The results reveal that amides have strongest inhibitive effect ranging from 4 to 38 %.  Thermodynamic parameters as well as adsorption isotherms were driven. Keywords: Electropolishing, amide derivatives Thermodynamic parameters, adsorptio

Investigation of Inhibition Effect of Acrylic acid on C-Steel Corrosion in Sulfuric Acid Solutions

Acrylic acid was tested as a corrosion inhibitor for C-steel in 0.5 M H2SO4 using gasometry, weight loss, and galvanostatic polarization techniques. Polymeric film is built up by cyclic voltammetry technique. The potentiodynamic polarization is used to examine the inhibition effect with the coated polymeric film. The data obtained from the different techniques coincide in that acrylic acid is a good mixed-type inhibitor. The inhibition process is based on the adsorption of acrylic acid on the surface of C-steel according to Temkin’s adsorption isotherm. The inhibition efficiency increases with inhibitor concentration and decreases with temperature. The thermodynamic parameters ΔE, ΔH*, ΔS*, and ΔG*ads were calculated to elaborate the mechanism of corrosion inhibition

Oxide Film Destruction on Al-Mg Alloys in HCl Solutions

Open circuit potential technique is used to follow the oxide film destruction of three of Al-Mg alloys in HCl solutions of varying concentrations.  Dissolution of the passive film on pare metal surface takes place in two distinct steps indicating that the film is composed mainly of a barrier layer of Al2O3 adjacent to the metal surface and an outer porous modification on the top of the first one. The rates of oxide film destruction and/or dissolution (δ1¯ and δ2¯) follow a direct logarithmic law. The extent of oxide film destruction and metal dissolution were found to increase with increasing the acid concentration and the percent of Mg content in the alloy sample

Inhibitive Effect of Urea and Urea Derivatives on the Corrosion of Silver in Acetic Acid Solutions

The corrosion of silver in acetic acid was studied using potentiodynamic polarization technique in absence and presence of different concentrations of urea, thiourea and N-allylthiourea. The inhibition efficiency was found to depend on both the inhibitor type and concentration. The inhibitive action of these compounds is based on the formation of salt complex and/or the adsorption of the protonated species on the metal surface according to Temkin's isotherm. The thermodynamic parameters Kads and ΔG°ads for the adsorption process are calculated and discussed

Inhibition effect of famotidine towards the corrosion of C-steel in sulphuric acid Solution

The inhibition effect of  famotidine drug  towards  the corrosion of C-steel in 0.5M H2SO4 was studied using weight loss, gasometry, potentiodynamic polarization and electrochemical frequency modulation (EFM) techniques, as well as, surface examination by SEM. The inhibition mechanism of FA is based on the adsorption process forming a film barrier layer protect the steel from acid attack. The adsorption is found to obey Frundlich model. The inhibition efficiency increased by increasing inhibitor concentration and decreased with temperature. Some thermodynamic parameters for adsorption process are deduced and discussed. Keywords: C-steel, famotidine, Adsorption, Corrosion

Physico-chemical studies of some aminobenzoic acid hydrazide complexes

The stability constants and related thermodynamic functions characterizing the formation of divalent Ni, Cu, Zn, Cd and Hg complexes with o- and p-aminobenzoic acid hydrazide were determined potentiometrically at different temperatures. The formations of the complexes are endothermic processes. The formed bonds are mainly electrostatic. Conductometric titration was carried out to determine the stoichiometry and stability of the formed complexes. The structures of complexes were characterized by their IR, 1H-NMR and 13C-NMR spectra, as well as X-ray diffractograms. The coordination process takes place through the carbonyl group and the terminal hydrazinic amino group. The thermal stability of the complexes was followed in the temperature range 20600ºC

Initiation and inhibition of pitting corrosion on reinforcing steel under natural corrosion conditions

Initiation and inhibition of pitting corrosion on reinforcing steel in saturated, naturally aerated Ca(OH)2 solutions, under natural corrosion conditions, are followed through measurements of corrosion current, electrochemical impedance spectroscopy and SEM investigation. Induction period for pit initiation and limiting corrosion current for pit propagation are found to depend on aggressive salt anion and cation-types, as well as, concentration. Ammonium chlorides and sulfates are more corrosive than the corresponding sodium salts. Benzotriazole and two of its derivatives are found to be good inhibitors for pitting corrosion of reinforcing steel. Adsorption of these compounds follows a Langmuir adsorption isotherm. The thermodynamic functions ?E?, ?H? and ?S? for pitting corrosion processes in the absence and presence of inhibitor are calculated and discussed.Scopu