F.H. Kármán

Corrosion inhibition by 1-hydroxy-ethane-1,1-diphosphonic acid : an electrochemical impedance spectroscopy study

Impedance spectra of carbon steel in the presence of 1-hydroxy-ethane-1,1-diphosphonic acid (HEDP) has been investigated in neutral solutions. The aim of the measurements was to study the effect of HEDP on the carbon steel corrosion as a function of inhibitor concentration. An optimal inhibitor concentration was found. A two-time constant equivalent circuit model including a constant phase element was consistent with experimental data in the frequency range studied. The system parameters, obtained by a nonlinear fit procedure are discussed in terms of the model used. Inhibitor efficiencies derived from impedance data are compared with those obtained from polarization and weight loss measurements. Results of these investigations show that a low concentrations, HEDP inhibits carbon steel corrosion by a precipitation mechanism forming insoluble iron complexes and repairing the porous oxide layer formed n the metal surface. Increasing HEDP concentration beyond the optimal value decreases its inhibition efficiency due to the dissolution of the oxide layer.

Effects of Bivalent Cations on Corrosion Inhibition of Steel by 1‐Hydroxyethane‐1,1‐diphosphonic Acid

The influence of calcium and zinc ions on the corrosion inhibition effect of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) on carbon steel has been investigated by electrochemical techniques, X-ray photoelectron spectroscopy, and atomic force microscopy. Addition of calcium or zinc ions greatly increased the inhibition efficiency of HEDP in a synergistic manner. The highest inhibition effect was obtained for molar ratios of Ca/HEDP = 0.5 and Zn/HEDP = 3 for 3 X 10 -4 mol dm -3 HEDP. The corrosion inhibition mechanism in the presence of these additives proved to be different from that with HEDP alone and was related to the formation of different complex species between HEDP and cation additives. The frequency response of the studied system was described by a transfer function containing two relaxation time constants corresponding to the charge-transfer process and the porous oxide layer. Higher zinc and phosphorous content in the inhibitor layer and a continuous change in the O-Fe and HO-Fe ratio were achieved by increasing zinc concentration in the solution (in the range Zn/HEDP = 0.5-3) as supported by XPS measurements. Changes in the chemical structure were established in the oxide-hydroxide layer developed spontaneously on the steel surface. The synergistic effect of inhibitor compounds appeared also in surface morphology, leading to the development of smooth, i.e., dense, protective layers as revealed by atomic force microscopy.

The role of oxide layer formation during corrosion inhibition of mild steel in neutral aqueous media

Abstract The influence of phosphonic acid with Ca cation on iron surfaces in neutral aerated media (0.5 mol dm − NaClO 4 ) has been studied by electrochemical and surface analytical methods. X-ray induced photoelectron (XPS) and Auger electron spectroscopy (XAES) provided the possibility for identification of different chemical states of the constituents of the corrosion protective layers. The presence of certain cations led to a synergistic effect. It was found that calcium ions were incorporated into the film that developed on the mild steel surface, containing a mixed oxide and hydroxide complex. Electrochemical Impedance Spectroscopy (EIS) was used to determine the inhibitor efficiency of phosphonic acid at different concentrations. The data obtained were fitted and modelled by an equivalent circuit model.

Corrosion and scale inhibitors with systematically changed structure

Abstract The corrosion inhibiting properties of some substituted carboxylic acids were studied with respect to the corrosion of mild steel in neutral solutions. Corrosion inhibition varied with the nature of the substituted components. The concentration dependence of inhibition was determined for the most efficient compounds.

Modeling of scale formation and corrosion from geothermal water

Abstract Simulation of particle size evolution and of scale formation and corrosion along the flow path is of the greatest importance for data interpretation as well as for engineering applications ( eg minimisation of the scale formation) in geothermal and hot water plants. An equilibrium simulation algorithm and a computer program for calcite scale formation in a CaCO 3  H 2 OCO 2 system has been developed using the Davies and Pitzer activity calculation methods. An equilibrium simulation algorithm and a computer program for CaCO 3 , CaSO 4 , BaSO 4 , SrSO 4 scale formation in a NaKMgCaHBaSrClBrSO 4  OHHCO 3 CO 3 CO 2 H 2 O system are also constructed using the Davies and the Pitzer activity calculation methods. The program determines the Langelier and Ryznar saturation indexes too, which are useful for the description of the scaling and corrosion characteristics in a solution. An equilibrium simulation algorithm and a computer program for the determination of the bubble point and of the partial pressure profiles of the gases CO 2 , CH 4 and N 2 between the bubble point depth and the well head in a geothermal well are constructed.

Inhibition efficiency of N-containing carboxylic and carboxy-phosphonic acids

Abstract Organic compounds for protection against corrosion—mainly amino carboxylic acids and their N -phosphonomethyl derivatives -with or without additives (zinc or metavanadate ion) have been studied in neutral solution by three different methods via impedance spectroscopy, weight loss and potentiostatic polarization in order to show the significance of CH 2 -PO 3 H 2 substitution and to detect a synergism in the presence of metals. For understanding the synergistic effect the stability of the zinc ion complex with organic acids was determined pH-metrically.

Preliminary investigations of scaling and corrosion in high enthalpy geothermal wells in Hungary

Abstract A solubility equilibrium program GEOPROF was applied to the determination of the bubble-point depth, pressure and temperature, as well as the partial pressure profiles of the gases CO 2 , CH 4 and N 2 between the bubble-point depth and the wellhead, in two high enthalpy geothermal wells, NSZ-2 and FAB-4 in southern Hungary. The pH, alkalinity, total carbonates, and equilibrium solubility for CaCO 3 , CaSO 4 , BaSO 4 , and SrSO 4 along the well depth profile in the Na–K–Mg–Ca–H–Ba–Sr–Cl–Br–SO 4 –OH–HCO 3 –CO 3 –CO 2 –H 2 O system were also determined and the concentrations of Ca 2+ , Ba 2+ , Sr 2+ , H + , OH − , HCO 3 − , CO 3 2− , and H 2 CO 3 * were computed at the actual temperature and CO 2 pressure using the Davies and Pitzer activity calculation methods. The calculated amounts of CaCO 3 scaling along the wells and at the surface were used in estimating service life. The results for well FAB-4 contain high uncertainties because of the estimated gas separation analysis data.

Dispersibility of Carbon Nanotubes

Availability of a stable carbon nanotube suspension is a prerequisite for production of polymer composites with carbon nanotube as additives. In this work nanotube suspensions, which have been prepared from various nanotubes in different dispersion agents, were compared. Dispersibility of the samples was investigated by scanning electon microscopy and atomic force microscopy. Solution of a non-ionic surfactant was also used successfully as a new dispersion agent. Geometrical parameters of the carbon nanotubes were determined by using atomic force microscopy. Correlation was found between the dispersibility and the parameters of the nanotubes and relative permittivity of the different solvents.

Potential-time measurements on mild steel in etch primer solutions

Abstract Experiments were carried out in a two pack system; polyvinyl butyral, zinc tetroxychromate in one pack, and phosphoric acid in the other with an isopropanol solvent in both packs. This study examines the functions of the phosphoric acid and the chromate containing pigment separately by utilising the feature that the alcohol dispersed components have sufficient conductivity to carry out potential-time measurements in the wet components before and during mixing.

Environmentally Friendly Corrosion Inhibitors

The sections in this article are Introduction Electrochemical Corrosion and Inhibition Routes to the Development of Corrosion Inhibitors Corrosion Inhibition by 1-Hydroxy-Ethane-1,1-Diphosphonic Acid (HEDP) Complexing Agent (HEDP—Iron) Multifunctional Inhibitor Molecules N-Acyl Amino Acids The Impact of the Acyl Moiety and the Amino Acid Side Chain on the Corrosion Inhibition of Mild Steel Corrosion Inhibition of Stainless Steel by Acylated Amino Acids Interaction of Unsaturated Organic Inhibitors with Mild Steel Influence of Aryl and Aralkenyl Amino Acid Derivatives on Mild Steel Corrosion Inhibition Efficiency of Carboxy and/or Phosphonic Acids Inhibition of Copper by Benzo-Hydroxamic Acids of Systematically Changed Structure Synergism Effect of Bivalent Cations on the Inhibition Efficiency of HEDP Adsorption of HEDP-Zn2+ on a Gold Surface Impedance Study of Synergistic Inhibition Study of the Surface Morphology by AFM (Atomic Force Microscopy) Surface analytical Study of Corrosion Inhibition Mechanisms Effect of Surface Pretreatment Effect of Inhibitor Concentration Effect of Bivalent Cations on Inhibitor Adsorption Quantitative Relationships between the Chemical Structure and Efficiency of Corrosion Inhibitors Conclusions Acknowledgements