The points raised in the paper entitled “Comments on the paper entitled ‘The formulation and modelling of the anodic dissolution of zinc through adsorbed intermediates”’ have been discussed. It has been shown that, in contrast to the statements in the “Comments”, most of the papers concerning the reaction schemes suggested for the interpretation of the dissolution or deposition of metals, which were considered as a support for the opinion of the Authors of the “Comments”, support the views expressed in our original paper [J. Electroanal. Chem. 583 (2005) 148]. On the other hand, it has been stressed again that the criticism expressed in the original paper refers to dubious conclusions drawn on the basis of transient measurements.

The problem of the stability of perchlorate ions in the presence of iron group metals is discussed. It is suggested that electrochemists should consider the reduction process as important evidence that should be taken into account. It has been shown that the mechanical properties of the passive layer on nickel are influenced by the presence of Cl− ions, presumably because chloride ions incorporated in the passive film facilitate the formation of a more ordered structure.

The problem of the distinction between the so-called free charge and the thermodynamic (total) charge of electrodes was discussed in the light of the relevant IUPAC definitions calling attention to the strict relationships existing between charge and mass balances during the formation of a double layer at electrodes or/and particles. It is demonstrated that the origins of controversial views concerning partial charge transfer and electrosorption valency, notions widely used nowadays in the electrochemical literature, could be ascribed to confusion of the free and thermodynamic charges. Although there are, even if sporadic, evidences and theoretical considerations in the literature proving that electrosorption valency as usually defined is an extrathermodynamic and self-contradictory concept, it is widely used by many authors for the interpretation of electrosorption phenomena. One of the most important aims of the present work was to demonstrate that independent of the thermodynamic considerations, the concept of electrosorption valency cannot be reconciled with elementary laws of electrochemistry. On the basis of analysis of real processes occurring in the interfacial layer of electrodes it was urged to avoid the treatment of some double-layer phenomena in terms of electrosorption valency in order to eliminate far-reaching misinterpretations leading to serious contradictions.

Some problems in connection with the simulation of Cl electrosorption on Ag(100) reported in Electrochimica Acta 50 (2005) 5518 are discussed.It is concluded, that although the electrostatic model could be correct, the results of the simulation can be hardly reconciled with the experimental data owing to the contradictions discussed in the present paper. (c) 2006 Elsevier Ltd. All rights reserved.

Dissolution mechanisms suggested for Zn have been discussed. It has been shown that the anions adsorbed on the metal or metal hydroxide surfaces play an important role in the dissolution process, therefore involvement of anions in the charge and mass balance cannot be neglected. An attempt has been made to demonstrate that without taking into account the real meaning of charge transfer processes, the application of the suggested mechanism and the relevant kinetic equations may lead to serious problems in the interpretation of the experimental results.

The problem of the stability of perchlorate ions in the presence of iron group metals is discussed in the light of new experimental results obtained at various temperatures, perchlorate concentrations and pH values. Results obtained with Fe, Co and Ni were compared. It was found that the behavior of nickel in perchlorate solution significantly differs from that of Fe and Co, which have very similar and significant reactivity in the reaction with perchlorate ions. Although the reaction rate with nickel is slow, its role cannot be neglected. The reduction of ClO4- ions in contact with iron group metals, first of all with Fe and Co, is so pronounced that it seems inevitable to revise many statements in text-books and monographs dealing with systems containing iron group metal and perchlorates. It is suggested that electrochemists should consider the reduction process as important evidence that should be taken into account. This also involves that all experimental results and their mechanistic interpretation concerning this field should be revisited.

Critical remarks have been formulated in connection with the surface stress measurements reported by Tian et al. It has been shown that due to the shortcomings of the experimental procedure some conclusions of the authors are hardly acceptable.

The adsorption of radiolabelled Cl− and SO4− ions from aqueous perchlorate solutions onto powdered Mn metal was studied. It was found that the extent of the adsorption is determined by the continuous increase of the thickness of the surface oxide/hydroxide layer formed as a consequence of the slow corrosion of the metal in neutral or quasi-neutral media. At low pH values (pH < 6) the extent of the adsorption decrease significantly owing to the dissolution of the surface layer. At high pH values (pH > 10) the adsorption decreases presumably owing to the competitive adsorption of OH− ions or the modification of the adsorption centres by some kind of deprotonation.

This chapter examines the liquid/fluid interfaces. These interfaces play an important role in many chemical and biological systems in addition to being interesting model systems for the study of the statistical physics of interfaces and membranes. The industrial utilization of materials with liquid/fluid interfaces, either in processing or in the finished product, is vast. Biopolymers, especially proteins and hydrocolloids, are used in foods to stabilize dispersed systems, such as food foams and oil-in-water emulsions, and also to control rheological and textural properties of foods. Because proteins are amphiphilic and exhibit a high tendency to adsorb to air/water and oil/water interfaces, they primarily function as emulsifiers in foods. Direct determination of the amount of species adsorbed per unit area of liquid/gas or liquid/liquid interface is not generally undertaken because of the difficulty of isolating the interfacial region from the bulk phase.

On the basis of the comparative radiotracer study of the adsorption of sulfate and pertechnetate ions on gamma-Al2O3, it is shown that the application of the radiotracer technique allows us to distinguish specific and nonspecific adsorption without the knowledge and the use of quantitative data as to the extent of the adsorption or the surface area of the adsorbent. It is demonstrated that the study of the adsorption of the TcO4- ion offers a tool for the investigation of electrostatic effects at the Al2O3/electrolyte interface.

The specific adsorption of sulfate ions on powdered Cr was studied by a radiotracer technique using 35S-labeled sulfuric acid in low concentration (c<10−3 mol dm−3) in the presence of a large excess of perchlorate supporting electrolyte. The pH and concentration dependence were determined. On the basis of a comparison of the results obtained for Cr2O3 and Cr, it can be assumed that, similar to other metals, the overall sorption behavior of Cr is determined by the protective oxide film present on the surface.

The problem of the reduction of perchlorate ions is discussed in the light of recent results bearing in mind the perchlorate environmental contamination challenge and recent problems concerning the electrochemical stability of ClO4− ions. The catalytic and electrocatalytic transformations are compared in the case of WC and Pt electrodes (catalysts). Various methods for the detection of the occurrence of the reduction process are presented (radiotracer technique, potential step method and voltammetry). It is shown that the interpretation of the results of studies of corrosion processes of Al, Zn, Cu, Ni and Fe carried out in the presence of ClO4− ions cannot be considered as adequate without taking into consideration the reduction of ClO4− ions and all previous work should be revisited on the basis of the new findings. Some elements of the mechanistic aspects of the complicated reduction processes are discussed.

The specific adsorption of radiolabeled sulfate ions from perchlorate supporting electrolyte onto TiO2 powder (anatase) has been investigated. The pH and concentration dependence of the adsorption was determined. Langmuir-like adsorption behavior similar to that on other oxides was found. From the pH dependence it follows that the protonation of the surface should precede the specific anion adsorption. The results obtained are compared with those reported for TiO2 bulk electrodes.

The pH and concentration dependence of the adsorption of sulfate ions on powdered Bi 2 O 3 was studied by a radiotracer technique in the presence of a large excess of perchlorate supporting electrolyte. It was found that, similar to other oxides such as Al 2 O 3 , Cr 2 O 3 and Fe 2 O 3 , the extent of adsorption is determined by the protonation of the Bi 2 O 3 surface. The redox transformations of Bi adatom layers are discussed in the light of the results obtained. It is established that for the interpretation of the redox processes occurring at the Bi/electrolyte interface the role of protonation of the oxide formed and the anion adsorption induced by the oxide layer should be taken into consideration.

The occurrence of the reduction of ClO4− ions in the course of the dissolution (corrosion) of Co was indicated through the study of the adsorption of radio labelled (36Cl) Cl− ions. A detailed analytical study determining the Co2+ and Cl− content of the solution phase furnished firm evidences that under suitable chosen experimental conditions the 4Co+ClO4−+8H+=4Co2++Cl−+4H2O reaction could be as important as the Co+2H+=Co2++H2 reaction considered in the literature as the only reaction path.

The specific adsorption of radiolabeled sulfate and phosphate ions from perchlorate supporting electrolyte onto nano-AlOOH and nano-Fe2O3 powder has been investigated. The pH dependence of the adsorption of anions onto nanopowders was compared with that of the same ions onto γ-Al2O3 and hematite. It was demonstrated that the character of the pH dependence of the adsorption is very similar in the comparable cases. It was found, however, that in contrast to the behavior of γ-Al2O3, nano-AlOOH dissolves at a significant rate at low pH values (pH<2). Thus the study of the pH dependence of the anion adsorption encounters difficulties at these pH values. Disregarding this fact, it can be concluded that no special effects can be observed in the anion adsorption onto the nano-oxides studied.

The problem of the application of perchloric acid and/or perchlorate supporting electrolyte in electrochemical and corrosion studies is discussed. It is demonstrated that in contrast to the general view in the literature the reduction of perchlorate ions could be an important step in the overall process occurring in the course of spontaneous dissolution of some metals in acid perchlorate medium. It is shown that especially in the case of the dissolution of iron the reduction of ClO4− leading to the formation of Cl− plays a substantial role. Consequently, all interpretations concerning the dissolution of iron in the presence of ClO4− ions should be revisited taking into consideration the possibility of the reduction process.

Combined EQCM and voltammetric studies in conjunction with radiotracer adsorption investigations were carried out in order to obtain direct information on the interfacial behavior of the Cu2+–Cu system under equilibrium and dynamic conditions with the aim of clarifying the role and participation of Cu+ ions formed by the interaction of cupric ions and copper metal. The appearance and accumulation of Cu+ ions in the solution phase is clearly demonstrated through radiotracer experiments using labeled Cl− ions. The formation of bulk CuCl phase is preceded by the formation of a CuCl surface layer. Data obtained from combined voltammetric and EQCM studies allow us to separate the potential regimes where the electrosorption, the formation of Cu+ or Cu2+ ions, and dissolution of CuCl are the predominant processes.