Cathodic Pretreatment Research Articles

Voltammetric and galvanostatic studies of hydrous and anhydrous iridium oxide films

Electrolytically grown hydrous oxide films on iridium wire electrodes have been thermally treated from 473 to 773 K. Anhydrous oxide films formed by this treatment have been subjected to cathodic polarization at the potential of the hydrogen evolution reaction, square-wave pulsing of potential from −0.25 to +1.25 V with respoect to SCE and to anodic galvanostatic polarization in 0.5 mol dm−3 H2SO4. Cathodic pretreatment caused an increase of the voltammetric charge in the oxide formation region while the square-wave pulsing formed a hydrous oxide film whose voltammetric charge was superimposed on the charge of the anhydrous oxide film. Both procedures restored the hydrophilic nature of the electrode/solution interface. Potential-time curves during anodic galvanostatic polarization served as a diagnostic criterion for the stability and the state of the oxide film.

ChemInform Abstract: Cathodic Codeposition of Cadmium Telluride on Conducting Glass.

AbstractIt is demonstrated that high quality, adherent cadmium telluride films of up to 5 μm thickness can be deposited on glass plates covered with a conductive tin oxide film after a cathodic pretreatment of the tin oxide film.

アルミニウムエッチングの前処理としてのＮａＯＨ洗浄とカソード処理の検討

Electrochemical investigation of NaOH cleaning was carried out as a pretreatment for etching of electrolytic capacitors. An attemp was made using electrochemical equipment to clarify the relation between NaOH cleaning and cathodic pretreatment. It was found that surface treatment of aluminum by NaOH cleaning is electrochemically equvalent to cathodic treatment in a deaerated NaCl solution.

Potentiometric monitoring of proteins. Part IV. Application to electrophoresis gels.

A simple method for the determination of proteins separated by gel electrophoresis is described based on direct potentiometry with copper electrodes. Results are presented for a number of proteins in agarose gels. Several different electrode designs are considered and the effects of various buffer systems are investigated. It is shown that cathodic pre-treatment of the monitoring electrodes gives a fast and reproducible response which is sufficient to form the basis of a simple, reliable and inexpensive method for the quantitative monitoring of proteins in electrophoresis gels.

Potentiometric monitoring of proteins. Part 3.—Direct potentiometry with a copper electrode

Results are presented for the direct potentiometric determination of L-cysteine, L-histidine and a number of proteins with copper electrodes which are cathodically treated before measurement. Comparisons are made with untreated and chemically treated electrodes. It is shown that provided the cathodic pretreatment technique is used the electrode response is fast and reproducible enough for the method to form the basis of a simple, reliable and inexpensive procedure for the monitoring of proteins. The Nernstian responses and equilibration times, together with the improved behaviour of the electrochemically pretreated electrodes, are discussed in terms of various models for the complexation of copper with amino acids and proteins.

Influence of cathodic reduction on the photoelectrochemical behaviour of titanium dioxide under UV radiation measurement of the photocurrent in chloride medium

It is established that a cathodic pretreatment of thermic titanium dioxide increases considerably the photoresponse to TiO 2 under uv radiation in chloride solution. The effects of the duration of the pretreatment and of the nature of the acidic media used to perform the cathodic pretreatment are investigated. The variation law of the increase of the photocurrent with the pretreatment duration, which is the sum of two exponential laws at least, reveals the presence of various phenomena in the improvement of the energetic efficiency. The various mechanism involved there are discussed according to different hypotheses.

The anodic dissolution process on active iron in alkaline solutions

Steady state anodic polarization curves were taken for Armco iron and in some experiments for high purity Puratronic iron in KOH solutions in the concentration range 5 x 10 −2-5M. After the 30 min cathodic pretreatment, well reproducible anodic Tafel plots are obtained. The experimentally obtained diagnostic criteria b a = 67–70 mV dec −1, n OH− = 1.1 and n HFeO 2 − = −0.45 are interpreted by the anodic reaction mechanism in which FeOH adsand Fe(OH) 2,ads appear as the intermediates adsorbed under Temkin conditions, the primary stable product of the electrode reaction being HFeO 2 −, and the final product Fe (OH) 2, formed by precipitation.

Effect of cathodic pretreatment on the passivation of iron in neutral solution

Pure iron specimens anodically oxidized at +600 mV ( vs sce) for one minute were partially reduced with a cathodic current of 10 μA/cm 2 and then reoxidized at the same potential for one hour. The experiment was performed in a boric acid/borate buffer solution at pH = 8.43 at room temperature. Variation in the thickness of the oxide film during the experiment is discussed for an inner Fe 3O 4 and outer γ-Fe 2O 3 layers, with emphasis on the effect of cathodic treatment. In the discussion, the amounts of charges for anodic and cathodic processes and the amount of dissolved Fe 2+ ions during the cathodic reduction are utilized.

Cathodic pretreatment of zinc and zinc-coated surfaces

Cathodic pretreatment of zinc and zinc-coated surfaces

Passivity of Zirconium In Sulfuric Acid Solutions–Effect of Cathodic Pretreatment

Abstract The effect of cathodic pretreatment at −1.3 V vs a saturated calomel electrode (SCE) on the passivity of Kroll zirconium in 5, 10, and 20 vol % H2SO4 solution at room temperature was determined through potentiostatic anodic polarization studies. The cathodic treatment made the attainment of passivity easier and reduced the passive currents considerably. Studies on potential vs time and active and passive currents vs time indicated a protective film formation during the cathodic treatment. The possibility of a zirconium oxide film formation due to cathodic polarization induced alkalinity at −1.3 V (SCE) is discussed.

Discussion on the paper “influence of cathodic pretreatment on the anodic dissolution kinetics of stainless steels in dilute acid media”

Discussion on the paper “influence of cathodic pretreatment on the anodic dissolution kinetics of stainless steels in dilute acid media”

Effects of mass-transport and oxide films on the cathodic reduction of O 2 on Ni

A study has been made of the effects of oxide films and mass-transport on the reduction of O 2 at rotating cylindrical Ni electrodes. In alkaline solutions the film of Ni(OH) 2 effectively stifles the steady-state mass-transport controlled O 2 reduction that occurs on bare Ni. The film is very persistent and its effects are observed at potentials below its legitimate potential range unless the metal is subjected to considerable cathodic pretreatment. In acid solutions Ni(OH) 2, said to form a prepassive porous film, has less effect on the reaction. It appears that there is a complete change in the kinetics with the formation of an oxide film and the reaction passes from mass transport control to severe activation control without an intervening mixed mass-transport-charge transfer control.

Influence of cathodic pretreatment on theanodic dissolution kinetics of stainless steels in dilute acid media

In the past 25 y electrochemical techniques have been utilized in a variety of programmes designed to produce alloys of superior corrosion resistance to specific environments. The potentio-dynamic polarization technique gives unique information on the passivation properties of steels. The data obtained from the above technique, however, can be subject to error if specific precautions are not taken in the experimental procedure. This paper describes the results of an investigation on the influence of cathodic pretreatment on the anodic-dissolution kinetics of AISI Types 430 and 304 stainless steel in dilute H 2SO 4. Laboratory tests on Type 304 stainless steel have shown that prolonged exposure to cathodic hydrogen evolution increases the magnitude of the critical anodic c.d. Also, cathodic pretreatment produces a passive current maxima, the amplitude of which is related to the duration of the cathodic pretreatment. The magnitude of the effect is markedly different on ferritic steels compared with austenitic steels, being greater for the ferritic steels because of the higher diffusivity of hydrogen in a body-centered cubic lattice. These data show that previous theories about the cause of passive current maxima, such as carbide precipitation following a sensitizing heat treatment, or Ni enrichment, are in error.

Influence of Prepolarization on the Electrochemical Behavior of Iron-Carbon Alloys

Abstract The influence of anodic and cathodic prepolarization of electrodes, containing respectively 0.03, 0.48, and 1.3 percent carbon, in de-aerated N and 0.1 N sulfuric acid at 25 C (77 F) on the subsequent open circuit potential-time curves has been determined. Anodic pretreatment always lowers and cathodic pretreatment raises the initial potential on these curves. Magnitude of the potential shift and time required to resume the rest potential are larger the higher the prepolarizing time. The influence of carbon content and acid concentration is complex. Special experiments have indicated the importance of specimen, and especially solution history, and have permitted an interpretation in terms of polarization diagrams. The most likely explanation is the influence of sulfide or noble metal or metalloid ions derived from the alloy or possibly the solution in altering the number of active anodic sites. This is achieved by an increase in the degree of hydrogen poisoning or by accumulation or plating out of metals or metalloids.

Enhanced Catalytic Activity of Platinum Electrodes resulting from Cathode Pretreatment

A RECENT report1,2 describes the effect on Raney platinum electrodes of cathodic pretreatment in 10N H2SO4. Current-voltage curves for the oxidation of formic acid in 3N H2SO4 before and after pretreatment were compared and the enhanced currents measured for the treated electrodes were attributed to an adsorbed layer of sulphur formed by deposition during the cathodic pretreatment. This is surprising because the inhibiting effect of sulphur adsorbed on platinum on many other surface reactions and electrode reactions is well known and was observed by Faraday3. Enhanced catalytic activity was also observed1,2 by using electrodes pretreated with gaseous hydrogen sulphide at high temperatures and with electrodes cathodically polarized in solutions of selenium oxide in dilute sulphuric acid. Extended cathodic pretreatment in 10 N H2SO4 yielded a less active electrode. Here, the sulphur was said to have formed a monolayer.

The Effect of Electrode Pretreatment on the Oxygen Reduction on Platinum in Perchloric Acid

The effect of pretreatment of a platinum electrode on the electrochemical reduction of oxygen and of hydrogen peroxide in perchloric acid was studied at room temperature. Hydrogen and oxygen pretreatments affect the oxygen reduction in a manner similar to cathodic and anodic pretreatments, respectively. An interpretation of various electrode characteristics is given on the basis of this parallelism. Removal of strongly bound oxygen by hydrogen pretreatment or cathodization accelerates the decomposition of hydrogen peroxide and increases the open‐circuit potential and the rate of the oxygen reduction in solutions containing 10−5 to 10−7M peroxide. Decay rates from a high anodic potential provide a sensitive measure for peroxide concentrations in the electrolyte.